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kpatch/kpatch-build/create-diff-object.c
Seth Jennings 392049a283 make symbol section change an error 
make symbol section change an error, except when moving out of an
ignored section

Signed-off-by: Seth Jennings <sjenning@redhat.com>
2014-07-28 14:09:33 -05:00

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/*
* create-diff-object.c
*
* Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
* Copyright (C) 2013-2014 Josh Poimboeuf <jpoimboe@redhat.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA,
* 02110-1301, USA.
*/
/*
* This file contains the heart of the ELF object differencing engine.
*
* The tool takes two ELF objects from two versions of the same source
* file; a "base" object and a "patched" object. These object need to have
* been compiled with the -ffunction-sections and -fdata-sections GCC options.
*
* The tool compares the objects at a section level to determine what
* sections have changed. Once a list of changed sections has been generated,
* various rules are applied to determine any object local sections that
* are dependencies of the changed section and also need to be included in
* the output object.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <error.h>
#include <gelf.h>
#include <argp.h>
#include <libgen.h>
#include <unistd.h>
#include "list.h"
#include "lookup.h"
#include "asm/insn.h"
#include "kpatch-patch.h"
#define ERROR(format, ...) \
error(1, 0, "%s: %d: " format, __FUNCTION__, __LINE__, ##__VA_ARGS__)
#define DIFF_FATAL(format, ...) \
({ \
printf("%s: " format "\n", objname, ##__VA_ARGS__); \
error(2, 0, "unreconcilable difference"); \
})
#define log_debug(format, ...) log(DEBUG, format, ##__VA_ARGS__)
#define log_normal(format, ...) log(NORMAL, "%s: " format, objname, ##__VA_ARGS__)
#define log(level, format, ...) \
({ \
if (loglevel <= (level)) \
printf(format, ##__VA_ARGS__); \
})
char *objname;
enum loglevel {
DEBUG,
NORMAL
};
static enum loglevel loglevel = NORMAL;
/*******************
* Data structures
* ****************/
struct section;
struct symbol;
struct rela;
enum status {
NEW,
CHANGED,
SAME
};
struct section {
struct list_head list;
struct section *twin;
GElf_Shdr sh;
Elf_Data *data;
char *name;
int index;
enum status status;
int include;
int ignore;
union {
struct { /* if (is_rela_section()) */
struct section *base;
struct list_head relas;
};
struct { /* else */
struct section *rela;
struct symbol *secsym, *sym;
};
};
};
struct symbol {
struct list_head list;
struct symbol *twin;
struct section *sec;
GElf_Sym sym;
char *name;
int index;
unsigned char bind, type;
enum status status;
union {
int include; /* used in the patched elf */
int strip; /* used in the output elf */
};
};
struct rela {
struct list_head list;
GElf_Rela rela;
struct symbol *sym;
unsigned char type;
int addend;
int offset;
char *string;
};
struct string {
struct list_head list;
char *name;
};
struct kpatch_elf {
Elf *elf;
struct list_head sections;
struct list_head symbols;
struct list_head strings;
int fd;
};
struct special_section {
char *name;
int (*group_size)(struct section *sec, int offset);
};
/*******************
* Helper functions
******************/
char *status_str(enum status status)
{
switch(status) {
case NEW:
return "NEW";
case CHANGED:
return "CHANGED";
case SAME:
return "SAME";
default:
ERROR("status_str");
}
/* never reached */
return NULL;
}
int is_rela_section(struct section *sec)
{
return (sec->sh.sh_type == SHT_RELA);
}
int is_debug_section(struct section *sec)
{
char *name;
if (is_rela_section(sec))
name = sec->base->name;
else
name = sec->name;
return !strncmp(name, ".debug_", 7);
}
struct section *find_section_by_index(struct list_head *list, unsigned int index)
{
struct section *sec;
list_for_each_entry(sec, list, list)
if (sec->index == index)
return sec;
return NULL;
}
struct section *find_section_by_name(struct list_head *list, const char *name)
{
struct section *sec;
list_for_each_entry(sec, list, list)
if (!strcmp(sec->name, name))
return sec;
return NULL;
}
struct symbol *find_symbol_by_index(struct list_head *list, size_t index)
{
struct symbol *sym;
list_for_each_entry(sym, list, list)
if (sym->index == index)
return sym;
return NULL;
}
struct symbol *find_symbol_by_name(struct list_head *list, const char *name)
{
struct symbol *sym;
list_for_each_entry(sym, list, list)
if (sym->name && !strcmp(sym->name, name))
return sym;
return NULL;
}
struct symbol *find_symbol_by_name_prefix(struct list_head *list,
const char *name)
{
struct symbol *sym;
int namelen = strlen(name);
list_for_each_entry(sym, list, list)
if (!strncmp(sym->name, name, namelen))
return sym;
return NULL;
}
#define ALLOC_LINK(_new, _list) \
{ \
(_new) = malloc(sizeof(*(_new))); \
if (!(_new)) \
ERROR("malloc"); \
memset((_new), 0, sizeof(*(_new))); \
INIT_LIST_HEAD(&(_new)->list); \
list_add_tail(&(_new)->list, (_list)); \
}
/* returns the offset of the string in the string table */
int offset_of_string(struct list_head *list, char *name)
{
struct string *string;
int index = 0;
/* try to find string in the string list */
list_for_each_entry(string, list, list) {
if (!strcmp(string->name, name))
return index;
index += strlen(string->name) + 1;
}
/* allocate a new string */
ALLOC_LINK(string, list);
string->name = name;
return index;
}
/*************
* Functions
* **********/
void kpatch_create_rela_list(struct kpatch_elf *kelf, struct section *sec)
{
int rela_nr, index = 0, skip = 0;
struct rela *rela;
unsigned int symndx;
/* find matching base (text/data) section */
sec->base = find_section_by_name(&kelf->sections, sec->name + 5);
if (!sec->base)
ERROR("can't find base section for rela section %s", sec->name);
/* create reverse link from base section to this rela section */
sec->base->rela = sec;
rela_nr = sec->sh.sh_size / sec->sh.sh_entsize;
log_debug("\n=== rela list for %s (%d entries) ===\n",
sec->base->name, rela_nr);
if (is_debug_section(sec)) {
log_debug("skipping rela listing for .debug_* section\n");
skip = 1;
}
/* read and store the rela entries */
while (rela_nr--) {
ALLOC_LINK(rela, &sec->relas);
if (!gelf_getrela(sec->data, index, &rela->rela))
ERROR("gelf_getrela");
index++;
rela->type = GELF_R_TYPE(rela->rela.r_info);
rela->addend = rela->rela.r_addend;
rela->offset = rela->rela.r_offset;
symndx = GELF_R_SYM(rela->rela.r_info);
rela->sym = find_symbol_by_index(&kelf->symbols, symndx);
if (!rela->sym)
ERROR("could not find rela entry symbol\n");
if (rela->sym->sec && (rela->sym->sec->sh.sh_flags & SHF_STRINGS)) {
rela->string = rela->sym->sec->data->d_buf + rela->addend;
if (!rela->string)
ERROR("could not lookup rela string\n");
}
if (skip)
continue;
log_debug("offset %d, type %d, %s %s %d", rela->offset,
rela->type, rela->sym->name,
(rela->addend < 0)?"-":"+", abs(rela->addend));
if (rela->string)
log_debug(" (string = %s)", rela->string);
log_debug("\n");
}
}
void kpatch_create_section_list(struct kpatch_elf *kelf)
{
Elf_Scn *scn = NULL;
struct section *sec;
size_t shstrndx, sections_nr;
if (elf_getshdrnum(kelf->elf, &sections_nr))
ERROR("elf_getshdrnum");
/*
* elf_getshdrnum() includes section index 0 but elf_nextscn
* doesn't return that section so subtract one.
*/
sections_nr--;
if (elf_getshdrstrndx(kelf->elf, &shstrndx))
ERROR("elf_getshdrstrndx");
log_debug("=== section list (%zu) ===\n", sections_nr);
while (sections_nr--) {
ALLOC_LINK(sec, &kelf->sections);
scn = elf_nextscn(kelf->elf, scn);
if (!scn)
ERROR("scn NULL");
if (!gelf_getshdr(scn, &sec->sh))
ERROR("gelf_getshdr");
sec->name = elf_strptr(kelf->elf, shstrndx, sec->sh.sh_name);
if (!sec->name)
ERROR("elf_strptr");
sec->data = elf_getdata(scn, NULL);
if (!sec->data)
ERROR("elf_getdata");
sec->index = elf_ndxscn(scn);
log_debug("ndx %02d, data %p, size %zu, name %s\n",
sec->index, sec->data->d_buf, sec->data->d_size,
sec->name);
}
/* Sanity check, one more call to elf_nextscn() should return NULL */
if (elf_nextscn(kelf->elf, scn))
ERROR("expected NULL");
}
int is_bundleable(struct symbol *sym)
{
if (sym->type == STT_FUNC &&
!strncmp(sym->sec->name, ".text.",6) &&
!strcmp(sym->sec->name + 6, sym->name))
return 1;
if (sym->type == STT_FUNC &&
!strncmp(sym->sec->name, ".text.unlikely.",15) &&
!strcmp(sym->sec->name + 15, sym->name))
return 1;
if (sym->type == STT_OBJECT &&
!strncmp(sym->sec->name, ".data.",6) &&
!strcmp(sym->sec->name + 6, sym->name))
return 1;
if (sym->type == STT_OBJECT &&
!strncmp(sym->sec->name, ".bss.",5) &&
!strcmp(sym->sec->name + 5, sym->name))
return 1;
return 0;
}
void kpatch_create_symbol_list(struct kpatch_elf *kelf)
{
struct section *symtab;
struct symbol *sym;
int symbols_nr, index = 0;
symtab = find_section_by_name(&kelf->sections, ".symtab");
if (!symtab)
ERROR("missing symbol table");
symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
log_debug("\n=== symbol list (%d entries) ===\n", symbols_nr);
while (symbols_nr--) {
ALLOC_LINK(sym, &kelf->symbols);
sym->index = index;
if (!gelf_getsym(symtab->data, index, &sym->sym))
ERROR("gelf_getsym");
index++;
sym->name = elf_strptr(kelf->elf, symtab->sh.sh_link,
sym->sym.st_name);
if (!sym->name)
ERROR("elf_strptr");
sym->type = GELF_ST_TYPE(sym->sym.st_info);
sym->bind = GELF_ST_BIND(sym->sym.st_info);
if (sym->sym.st_shndx > SHN_UNDEF &&
sym->sym.st_shndx < SHN_LORESERVE) {
sym->sec = find_section_by_index(&kelf->sections,
sym->sym.st_shndx);
if (!sym->sec)
ERROR("couldn't find section for symbol %s\n",
sym->name);
if (is_bundleable(sym)) {
if (sym->sym.st_value != 0)
ERROR("symbol %s at offset %lu within section %s, expected 0",
sym->name, sym->sym.st_value, sym->sec->name);
sym->sec->sym = sym;
} else if (sym->type == STT_SECTION) {
sym->sec->secsym = sym;
/* use the section name as the symbol name */
sym->name = sym->sec->name;
}
}
log_debug("sym %02d, type %d, bind %d, ndx %02d, name %s",
sym->index, sym->type, sym->bind, sym->sym.st_shndx,
sym->name);
if (sym->sec)
log_debug(" -> %s", sym->sec->name);
log_debug("\n");
}
}
struct kpatch_elf *kpatch_elf_open(const char *name)
{
Elf *elf;
int fd;
struct kpatch_elf *kelf;
struct section *sec;
fd = open(name, O_RDONLY);
if (fd == -1)
ERROR("open");
elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
if (!elf)
ERROR("elf_begin");
kelf = malloc(sizeof(*kelf));
if (!kelf)
ERROR("malloc");
memset(kelf, 0, sizeof(*kelf));
INIT_LIST_HEAD(&kelf->sections);
INIT_LIST_HEAD(&kelf->symbols);
INIT_LIST_HEAD(&kelf->strings);
/* read and store section, symbol entries from file */
kelf->elf = elf;
kelf->fd = fd;
kpatch_create_section_list(kelf);
kpatch_create_symbol_list(kelf);
/* for each rela section, read and store the rela entries */
list_for_each_entry(sec, &kelf->sections, list) {
if (!is_rela_section(sec))
continue;
INIT_LIST_HEAD(&sec->relas);
kpatch_create_rela_list(kelf, sec);
}
return kelf;
}
int rela_equal(struct rela *rela1, struct rela *rela2)
{
if (rela1->type != rela2->type ||
rela1->offset != rela2->offset)
return 0;
if (rela1->string) {
if (rela2->string &&
!strcmp(rela1->string, rela2->string))
return 1;
} else {
if (strcmp(rela1->sym->name, rela2->sym->name))
return 0;
if (rela1->addend == rela2->addend)
return 1;
}
return 0;
}
void kpatch_compare_correlated_rela_section(struct section *sec)
{
struct rela *rela1, *rela2 = NULL;
rela2 = list_entry(sec->twin->relas.next, struct rela, list);
list_for_each_entry(rela1, &sec->relas, list) {
if (rela_equal(rela1, rela2)) {
rela2 = list_entry(rela2->list.next, struct rela, list);
continue;
}
sec->status = CHANGED;
return;
}
sec->status = SAME;
}
void kpatch_compare_correlated_nonrela_section(struct section *sec)
{
struct section *sec1 = sec, *sec2 = sec->twin;
if (sec1->sh.sh_type != SHT_NOBITS &&
memcmp(sec1->data->d_buf, sec2->data->d_buf, sec1->data->d_size))
sec->status = CHANGED;
else
sec->status = SAME;
}
void kpatch_compare_correlated_section(struct section *sec)
{
struct section *sec1 = sec, *sec2 = sec->twin;
/* Compare section headers (must match or fatal) */
if (sec1->sh.sh_type != sec2->sh.sh_type ||
sec1->sh.sh_flags != sec2->sh.sh_flags ||
sec1->sh.sh_addr != sec2->sh.sh_addr ||
sec1->sh.sh_addralign != sec2->sh.sh_addralign ||
sec1->sh.sh_entsize != sec2->sh.sh_entsize)
DIFF_FATAL("%s section header details differ", sec1->name);
/* Short circuit for mcount sections, we rebuild regardless */
if (!strcmp(sec->name, ".rela__mcount_loc") ||
!strcmp(sec->name, "__mcount_loc")) {
sec->status = SAME;
goto out;
}
if (sec1->sh.sh_size != sec2->sh.sh_size ||
sec1->data->d_size != sec2->data->d_size) {
sec->status = CHANGED;
goto out;
}
if (is_rela_section(sec))
kpatch_compare_correlated_rela_section(sec);
else
kpatch_compare_correlated_nonrela_section(sec);
out:
if (sec->status == CHANGED)
log_debug("section %s has changed\n", sec->name);
}
void kpatch_compare_sections(struct list_head *seclist)
{
struct section *sec;
list_for_each_entry(sec, seclist, list) {
if (sec->twin)
kpatch_compare_correlated_section(sec);
else
sec->status = NEW;
/* sync symbol status */
if (is_rela_section(sec)) {
if (sec->base->sym && sec->base->sym->status != CHANGED)
sec->base->sym->status = sec->status;
} else {
if (sec->sym && sec->sym->status != CHANGED)
sec->sym->status = sec->status;
}
}
}
void kpatch_compare_correlated_symbol(struct symbol *sym)
{
struct symbol *sym1 = sym, *sym2 = sym->twin;
if (sym1->sym.st_info != sym2->sym.st_info ||
sym1->sym.st_other != sym2->sym.st_other ||
(sym1->sec && !sym2->sec) ||
(sym2->sec && !sym1->sec))
DIFF_FATAL("symbol info mismatch: %s", sym1->name);
/*
* If two symbols are correlated but their sections are not, then the
* symbol has changed sections. This is only allowed if the symbol is
* moving out of an ignored section.
*/
if (sym1->sec && sym2->sec && sym1->sec->twin != sym2->sec) {
if (sym2->sec->twin && sym2->sec->twin->ignore)
sym->status = CHANGED;
else
DIFF_FATAL("symbol changed sections: %s", sym1->name);
}
if (sym1->type == STT_OBJECT &&
sym1->sym.st_size != sym2->sym.st_size)
DIFF_FATAL("object size mismatch: %s", sym1->name);
if (sym1->sym.st_shndx == SHN_UNDEF ||
sym1->sym.st_shndx == SHN_ABS)
sym1->status = SAME;
/*
* The status of LOCAL symbols is dependent on the status of their
* matching section and is set during section comparison.
*/
}
void kpatch_compare_symbols(struct list_head *symlist)
{
struct symbol *sym;
list_for_each_entry(sym, symlist, list) {
if (sym->twin)
kpatch_compare_correlated_symbol(sym);
else
sym->status = NEW;
log_debug("symbol %s is %s\n", sym->name, status_str(sym->status));
}
}
void kpatch_correlate_sections(struct list_head *seclist1, struct list_head *seclist2)
{
struct section *sec1, *sec2;
list_for_each_entry(sec1, seclist1, list) {
list_for_each_entry(sec2, seclist2, list) {
if (strcmp(sec1->name, sec2->name))
continue;
sec1->twin = sec2;
sec2->twin = sec1;
/* set initial status, might change */
sec1->status = sec2->status = SAME;
break;
}
}
}
void kpatch_correlate_symbols(struct list_head *symlist1, struct list_head *symlist2)
{
struct symbol *sym1, *sym2;
list_for_each_entry(sym1, symlist1, list) {
list_for_each_entry(sym2, symlist2, list) {
if (!strcmp(sym1->name, sym2->name) &&
sym1->type == sym2->type) {
sym1->twin = sym2;
sym2->twin = sym1;
/* set initial status, might change */
sym1->status = sym2->status = SAME;
break;
}
}
}
}
void kpatch_compare_elf_headers(Elf *elf1, Elf *elf2)
{
GElf_Ehdr eh1, eh2;
if (!gelf_getehdr(elf1, &eh1))
ERROR("gelf_getehdr");
if (!gelf_getehdr(elf2, &eh2))
ERROR("gelf_getehdr");
if (memcmp(eh1.e_ident, eh2.e_ident, EI_NIDENT) ||
eh1.e_type != eh2.e_type ||
eh1.e_machine != eh2.e_machine ||
eh1.e_version != eh2.e_version ||
eh1.e_entry != eh2.e_entry ||
eh1.e_phoff != eh2.e_phoff ||
eh1.e_flags != eh2.e_flags ||
eh1.e_ehsize != eh2.e_ehsize ||
eh1.e_phentsize != eh2.e_phentsize ||
eh1.e_shentsize != eh2.e_shentsize)
DIFF_FATAL("ELF headers differ");
}
void kpatch_check_program_headers(Elf *elf)
{
size_t ph_nr;
if (elf_getphdrnum(elf, &ph_nr))
ERROR("elf_getphdrnum");
if (ph_nr != 0)
DIFF_FATAL("ELF contains program header");
}
/*
* When gcc makes compiler optimizations which affect a function's calling
* interface, it mangles the function's name. For example, sysctl_print_dir is
* renamed to sysctl_print_dir.isra.2. The problem is that the trailing number
* is chosen arbitrarily, and the patched version of the function may end up
* with a different trailing number. Rename any mangled patched functions to
* match their base counterparts.
*/
void kpatch_rename_mangled_functions(struct kpatch_elf *base,
struct kpatch_elf *patched)
{
struct symbol *sym, *basesym;
char *prefix, *dot;
list_for_each_entry(sym, &patched->symbols, list) {
if (sym->type != STT_FUNC)
continue;
if (!strstr(sym->name, ".isra.") &&
!strstr(sym->name, ".constprop.") &&
!strstr(sym->name, ".part."))
continue;
if (sym != sym->sec->sym)
ERROR("expected bundled section for %s\n", sym->name);
/* prefix of foo.isra.1.constprop.2 is foo.isra */
prefix = strdup(sym->name);
dot = strchr(prefix, '.');
dot = strchr(dot+1, '.');
*dot = '\0';
basesym = find_symbol_by_name_prefix(&base->symbols, prefix);
free(prefix);
if (!basesym)
continue;
if (!strcmp(sym->name, basesym->name))
continue;
log_debug("renaming %s to %s\n", sym->name, basesym->name);
sym->name = strdup(basesym->name);
sym->sec->name = strdup(basesym->sec->name);
if (sym->sec->rela)
sym->sec->rela->name = strdup(basesym->sec->rela->name);
}
}
/*
* gcc renames static local variables by appending a period and a number. For
* example, __key could be renamed to __key.31452. Unfortunately this number
* can arbitrarily change. Try to rename the patched version of the symbol to
* match the base version and then correlate them.
*/
void kpatch_correlate_static_local_variables(struct kpatch_elf *base,
struct kpatch_elf *patched)
{
struct symbol *sym, *basesym;
struct section *tmpsec, *sec;
struct rela *rela;
int prefixlen;
char *dot;
list_for_each_entry(sym, &patched->symbols, list) {
if (sym->type != STT_OBJECT || sym->bind != STB_LOCAL ||
sym->twin)
continue;
dot = strchr(sym->name, '.');
if (!dot)
continue;
prefixlen = dot - sym->name;
if (sym->name[prefixlen+1] < '0' ||
sym->name[prefixlen+1] > '9')
continue;
/* find the patched function which uses the static variable */
sec = NULL;
list_for_each_entry(tmpsec, &patched->sections, list) {
if (!is_rela_section(tmpsec) ||
is_debug_section(tmpsec))
continue;
list_for_each_entry(rela, &tmpsec->relas, list) {
if (rela->sym != sym)
continue;
if (sec)
ERROR("static local variable %s used by two functions",
sym->name);
sec = tmpsec;
break;
}
}
if (!sec)
ERROR("static local variable %s not used", sym->name);
if (!sec->twin)
continue;
/*
* Ensure there are no other orphaned static variables with the
* same prefix in the function. This is possible if the
* variables are in different scopes (using C braces).
*/
list_for_each_entry(rela, &sec->relas, list) {
if (rela->sym == sym || rela->sym->twin)
continue;
if (!strncmp(rela->sym->name, sym->name, prefixlen))
ERROR("found another static local variable matching %s in patched %s",
sym->name, sec->name);
}
/* find the base object's corresponding variable */
basesym = NULL;
list_for_each_entry(rela, &sec->twin->relas, list) {
if (rela->sym->twin)
continue;
if (strncmp(rela->sym->name, sym->name, prefixlen))
continue;
if (basesym)
ERROR("found two static local variables matching %s in orig %s",
sym->name, sec->name);
basesym = rela->sym;
}
if (!basesym)
continue;
if (sym != sym->sec->sym)
ERROR("expected bundled section for %s", sym->name);
if (basesym != basesym->sec->sym)
ERROR("expected bundled section for %s",basesym->name);
log_debug("renaming and correlating %s to %s\n",
sym->name, basesym->name);
sym->name = strdup(basesym->name);
sym->twin = basesym;
basesym->twin = sym;
sym->sec->twin = basesym->sec;
basesym->sec->twin = sym->sec;
sym->status = basesym->status = SAME;
}
}
void kpatch_correlate_elfs(struct kpatch_elf *kelf1, struct kpatch_elf *kelf2)
{
kpatch_correlate_sections(&kelf1->sections, &kelf2->sections);
kpatch_correlate_symbols(&kelf1->symbols, &kelf2->symbols);
}
void kpatch_compare_correlated_elements(struct kpatch_elf *kelf)
{
/* lists are already correlated at this point */
kpatch_compare_sections(&kelf->sections);
kpatch_compare_symbols(&kelf->symbols);
}
void rela_insn(struct section *sec, struct rela *rela, struct insn *insn)
{
unsigned long insn_addr, start, end, rela_addr;
start = (unsigned long)sec->base->data->d_buf;
end = start + sec->base->sh.sh_size;
rela_addr = start + rela->offset;
for (insn_addr = start; insn_addr < end; insn_addr += insn->length) {
insn_init(insn, (void *)insn_addr, 1);
insn_get_length(insn);
if (!insn->length)
ERROR("can't decode instruction in section %s at offset 0x%lx",
sec->base->name, insn_addr);
if (rela_addr >= insn_addr &&
rela_addr < insn_addr + insn->length)
return;
}
}
/*
* Mangle the relas a little. The compiler will sometimes use section symbols
* to reference local objects and functions rather than the object or function
* symbols themselves. We substitute the object/function symbols for the
* section symbol in this case so that the relas can be properly correlated and
* so that the existing object/function in vmlinux can be linked to.
*/
void kpatch_replace_sections_syms(struct kpatch_elf *kelf)
{
struct section *sec;
struct rela *rela;
struct symbol *sym;
int add_off;
list_for_each_entry(sec, &kelf->sections, list) {
if (!is_rela_section(sec))
continue;
list_for_each_entry(rela, &sec->relas, list) {
/*
* Replace references to bundled sections with their
* symbols.
*/
if (rela->sym->type == STT_SECTION &&
rela->sym->sec && rela->sym->sec->sym) {
rela->sym = rela->sym->sec->sym;
continue;
}
/*
* These are special data sections whose data symbols
* aren't bundled with sections when using
* -fdata-sections. We need to replace the section
* references with their corresponding objects.
*/
if (strcmp(rela->sym->name, ".data..percpu") &&
strcmp(rela->sym->name, ".data..read_mostly") &&
strcmp(rela->sym->name, ".data.unlikely") &&
!(rela->sym->type == STT_SECTION && rela->sym->sec &&
(rela->sym->sec->sh.sh_flags & SHF_EXECINSTR)))
continue;
list_for_each_entry(sym, &kelf->symbols, list) {
if (sym->type == STT_SECTION ||
sym->sec != rela->sym->sec)
continue;
if (rela->type == R_X86_64_PC32) {
struct insn insn;
rela_insn(sec, rela, &insn);
add_off = (long)insn.next_byte -
(long)sec->base->data->d_buf -
rela->offset;
} else if (rela->type == R_X86_64_64 ||
rela->type == R_X86_64_32S)
add_off = 0;
else
continue;
if (sym->sym.st_value != rela->addend + add_off)
continue;
rela->sym = sym;
rela->addend = -add_off;
break;
}
}
}
}
void kpatch_dump_kelf(struct kpatch_elf *kelf)
{
struct section *sec;
struct symbol *sym;
struct rela *rela;
if (loglevel > DEBUG)
return;
printf("\n=== Sections ===\n");
list_for_each_entry(sec, &kelf->sections, list) {
printf("%02d %s (%s)", sec->index, sec->name, status_str(sec->status));
if (is_rela_section(sec)) {
printf(", base-> %s\n", sec->base->name);
/* skip .debug_* sections */
if (is_debug_section(sec))
goto next;
printf("rela section expansion\n");
list_for_each_entry(rela, &sec->relas, list) {
printf("sym %d, offset %d, type %d, %s %s %d\n",
rela->sym->index, rela->offset,
rela->type, rela->sym->name,
(rela->addend < 0)?"-":"+",
abs(rela->addend));
}
} else {
if (sec->sym)
printf(", sym-> %s", sec->sym->name);
if (sec->secsym)
printf(", secsym-> %s", sec->secsym->name);
if (sec->rela)
printf(", rela-> %s", sec->rela->name);
}
next:
printf("\n");
}
printf("\n=== Symbols ===\n");
list_for_each_entry(sym, &kelf->symbols, list) {
printf("sym %02d, type %d, bind %d, ndx %02d, name %s (%s)",
sym->index, sym->type, sym->bind, sym->sym.st_shndx,
sym->name, status_str(sym->status));
if (sym->sec && (sym->type == STT_FUNC || sym->type == STT_OBJECT))
printf(" -> %s", sym->sec->name);
printf("\n");
}
}
void kpatch_verify_patchability(struct kpatch_elf *kelf)
{
struct section *sec;
int errs = 0;
list_for_each_entry(sec, &kelf->sections, list) {
if (sec->status == CHANGED && !sec->include) {
log_normal("changed section %s not selected for inclusion\n",
sec->name);
errs++;
}
/* ensure we aren't including .data.* or .bss.* */
if (sec->include &&
(!strncmp(sec->name, ".data", 5) ||
!strncmp(sec->name, ".bss", 4))) {
log_normal("data section %s selected for inclusion\n",
sec->name);
errs++;
}
}
if (errs)
DIFF_FATAL("%d unsupported section change(s)", errs);
}
#define inc_printf(fmt, ...) \
log_debug("%*s" fmt, recurselevel, "", ##__VA_ARGS__);
void kpatch_include_symbol(struct symbol *sym, int recurselevel)
{
struct rela *rela;
struct section *sec;
inc_printf("start include_symbol(%s)\n", sym->name);
sym->include = 1;
inc_printf("symbol %s is included\n", sym->name);
/*
* Check if sym is a non-local symbol (sym->sec is NULL) or
* if an unchanged local symbol. This a base case for the
* inclusion recursion.
*/
if (!sym->sec || sym->sec->include ||
(sym->type != STT_SECTION && sym->status == SAME))
goto out;
sec = sym->sec;
sec->include = 1;
inc_printf("section %s is included\n", sec->name);
if (sec->secsym && sec->secsym != sym) {
sec->secsym->include = 1;
inc_printf("section symbol %s is included\n", sec->secsym->name);
}
if (!sec->rela)
goto out;
sec->rela->include = 1;
inc_printf("section %s is included\n", sec->rela->name);
list_for_each_entry(rela, &sec->rela->relas, list)
kpatch_include_symbol(rela->sym, recurselevel+1);
out:
inc_printf("end include_symbol(%s)\n", sym->name);
return;
}
void kpatch_include_standard_elements(struct kpatch_elf *kelf)
{
struct section *sec;
list_for_each_entry(sec, &kelf->sections, list) {
/* include these sections even if they haven't changed */
if (!strcmp(sec->name, ".shstrtab") ||
!strcmp(sec->name, ".strtab") ||
!strcmp(sec->name, ".symtab"))
sec->include = 1;
}
/* include the NULL symbol */
list_entry(kelf->symbols.next, struct symbol, list)->include = 1;
}
void kpatch_include_hook_elements(struct kpatch_elf *kelf)
{
struct section *sec;
struct symbol *sym;
struct rela *rela;
/* include load/unload sections */
list_for_each_entry(sec, &kelf->sections, list) {
if (!strcmp(sec->name, ".kpatch.hooks.load") ||
!strcmp(sec->name, ".kpatch.hooks.unload") ||
!strcmp(sec->name, ".rela.kpatch.hooks.load") ||
!strcmp(sec->name, ".rela.kpatch.hooks.unload")) {
sec->include = 1;
if (is_rela_section(sec)) {
/* include hook dependencies */
rela = list_entry(sec->relas.next,
struct rela, list);
sym = rela->sym;
log_normal("found hook: %s\n",sym->name);
kpatch_include_symbol(sym, 0);
/* strip the hook symbol */
sym->include = 0;
/* use section symbol instead */
rela->sym = sym->sec->secsym;
} else {
sec->secsym->include = 1;
}
}
}
/*
* Strip temporary global load/unload function pointer objects
* used by the kpatch_[load|unload]() macros.
*/
list_for_each_entry(sym, &kelf->symbols, list)
if (!strcmp(sym->name, "kpatch_load_data") ||
!strcmp(sym->name, "kpatch_unload_data"))
sym->include = 0;
}
void kpatch_include_force_elements(struct kpatch_elf *kelf)
{
struct section *sec;
struct symbol *sym;
struct rela *rela;
/* include force sections */
list_for_each_entry(sec, &kelf->sections, list) {
if (!strcmp(sec->name, ".kpatch.force") ||
!strcmp(sec->name, ".rela.kpatch.force")) {
sec->include = 1;
if (!is_rela_section(sec)) {
/* .kpatch.force */
sec->secsym->include = 1;
continue;
}
/* .rela.kpatch.force */
list_for_each_entry(rela, &sec->relas, list)
log_normal("function '%s' marked with KPATCH_FORCE_UNSAFE!\n",
rela->sym->name);
}
}
/* strip temporary global kpatch_force_func_* symbols */
list_for_each_entry(sym, &kelf->symbols, list)
if (!strncmp(sym->name, "__kpatch_force_func_",
strlen("__kpatch_force_func_")))
sym->include = 0;
}
int kpatch_include_changed_functions(struct kpatch_elf *kelf)
{
struct symbol *sym;
int changed_nr = 0;
log_debug("\n=== Inclusion Tree ===\n");
list_for_each_entry(sym, &kelf->symbols, list) {
if (sym->status == CHANGED &&
sym->type == STT_FUNC) {
changed_nr++;
log_normal("changed function: %s\n", sym->name);
kpatch_include_symbol(sym, 0);
}
if (sym->type == STT_FILE)
sym->include = 1;
}
return changed_nr;
}
void kpatch_migrate_symbols(struct list_head *src,
struct list_head *dst,
int (*select)(struct symbol *))
{
struct symbol *sym, *safe;
list_for_each_entry_safe(sym, safe, src, list) {
if (select && !select(sym))
continue;
list_del(&sym->list);
list_add_tail(&sym->list, dst);
}
}
int is_null_sym(struct symbol *sym)
{
return !strlen(sym->name);
}
int is_file_sym(struct symbol *sym)
{
return sym->type == STT_FILE;
}
int is_local_func_sym(struct symbol *sym)
{
return sym->bind == STB_LOCAL && sym->type == STT_FUNC;
}
int is_local_sym(struct symbol *sym)
{
return sym->bind == STB_LOCAL;
}
void kpatch_migrate_included_elements(struct kpatch_elf *kelf, struct kpatch_elf **kelfout)
{
struct section *sec, *safesec;
struct symbol *sym, *safesym;
struct kpatch_elf *out;
/* allocate output kelf */
out = malloc(sizeof(*out));
if (!out)
ERROR("malloc");
memset(out, 0, sizeof(*out));
INIT_LIST_HEAD(&out->sections);
INIT_LIST_HEAD(&out->symbols);
INIT_LIST_HEAD(&out->strings);
/* migrate included sections from kelf to out */
list_for_each_entry_safe(sec, safesec, &kelf->sections, list) {
if (!sec->include)
continue;
list_del(&sec->list);
list_add_tail(&sec->list, &out->sections);
sec->index = 0;
if (!is_rela_section(sec) && sec->secsym && !sec->secsym->include)
/* break link to non-included section symbol */
sec->secsym = NULL;
}
/* migrate included symbols from kelf to out */
list_for_each_entry_safe(sym, safesym, &kelf->symbols, list) {
if (!sym->include)
continue;
list_del(&sym->list);
list_add_tail(&sym->list, &out->symbols);
sym->index = 0;
sym->strip = 0;
if (sym->sec && !sym->sec->include)
/* break link to non-included section */
sym->sec = NULL;
}
*kelfout = out;
}
void kpatch_reorder_symbols(struct kpatch_elf *kelf)
{
LIST_HEAD(symbols);
/* migrate NULL sym */
kpatch_migrate_symbols(&kelf->symbols, &symbols, is_null_sym);
/* migrate LOCAL FILE sym */
kpatch_migrate_symbols(&kelf->symbols, &symbols, is_file_sym);
/* migrate LOCAL FUNC syms */
kpatch_migrate_symbols(&kelf->symbols, &symbols, is_local_func_sym);
/* migrate all other LOCAL syms */
kpatch_migrate_symbols(&kelf->symbols, &symbols, is_local_sym);
/* migrate all other (GLOBAL) syms */
kpatch_migrate_symbols(&kelf->symbols, &symbols, NULL);
list_replace(&symbols, &kelf->symbols);
}
void kpatch_reindex_elements(struct kpatch_elf *kelf)
{
struct section *sec;
struct symbol *sym;
int index;
index = 1; /* elf write function handles NULL section 0 */
list_for_each_entry(sec, &kelf->sections, list)
sec->index = index++;
index = 0;
list_for_each_entry(sym, &kelf->symbols, list) {
sym->index = index++;
if (sym->sec)
sym->sym.st_shndx = sym->sec->index;
else if (sym->sym.st_shndx != SHN_ABS)
sym->sym.st_shndx = SHN_UNDEF;
}
}
int bug_table_group_size(struct section *sec, int offset) { return 12; }
int smp_locks_group_size(struct section *sec, int offset) { return 4; }
int parainstructions_group_size(struct section *sec, int offset) { return 16; }
int ex_table_group_size(struct section *sec, int offset) { return 8; }
int altinstructions_group_size(struct section *sec, int offset) { return 12; }
int fixup_group_size(struct section *sec, int offset)
{
unsigned char *insn, *start, *end;
/*
* Each fixup group is a collection of instructions. The last
* instruction is always 'jmpq'.
*/
start = sec->data->d_buf + offset;
end = start + sec->sh.sh_size;
for (insn = start; insn < end; insn++) {
/* looking for the pattern "e9 00 00 00 00" */
if (*insn == 0xe9 && *(uint32_t *)(insn + 1) == 0)
return insn + 5 - start;
}
ERROR("can't find jump instruction in .fixup section");
return 0;
}
struct special_section special_sections[] = {
{
.name = "__bug_table",
.group_size = bug_table_group_size,
},
{
.name = ".smp_locks",
.group_size = smp_locks_group_size,
},
{
.name = ".parainstructions",
.group_size = parainstructions_group_size,
},
{
.name = "__ex_table",
.group_size = ex_table_group_size,
},
{
.name = ".altinstructions",
.group_size = altinstructions_group_size,
},
{
.name = ".fixup",
.group_size = fixup_group_size,
},
{},
};
int should_keep_rela_group(struct section *sec, int start, int size)
{
struct rela *rela;
int found = 0;
/* check if any relas in the group reference any changed functions */
list_for_each_entry(rela, &sec->relas, list) {
if (rela->offset >= start &&
rela->offset < start + size &&
rela->sym->type == STT_FUNC &&
rela->sym->sec->status != SAME) {
found = 1;
log_debug("new/changed symbol %s found in special section %s\n",
rela->sym->name, sec->name);
}
}
return found;
}
void kpatch_regenerate_special_section(struct special_section *special,
struct section *sec)
{
struct rela *rela, *safe;
char *src, *dest;
int group_size, src_offset, dest_offset, include, align, aligned_size;
LIST_HEAD(newrelas);
src = sec->base->data->d_buf;
/* alloc buffer for new base section */
dest = malloc(sec->base->sh.sh_size);
if (!dest)
ERROR("malloc");
group_size = 0;
src_offset = 0;
dest_offset = 0;
for ( ; src_offset < sec->base->sh.sh_size; src_offset += group_size) {
group_size = special->group_size(sec->base, src_offset);
include = should_keep_rela_group(sec, src_offset, group_size);
if (!include)
continue;
/*
* Copy all relas in the group. It's possible that the relas
* aren't sorted (e.g. .rela.fixup), so go through the entire
* rela list each time.
*/
list_for_each_entry_safe(rela, safe, &sec->relas, list) {
if (rela->offset >= src_offset &&
rela->offset < src_offset + group_size) {
/* copy rela entry */
list_del(&rela->list);
list_add_tail(&rela->list, &newrelas);
rela->offset -= src_offset - dest_offset;
rela->rela.r_offset = rela->offset;
rela->sym->include = 1;
}
}
/* copy base section group */
memcpy(dest + dest_offset, src + src_offset, group_size);
dest_offset += group_size;
}
/* verify that group_size is a divisor of aligned section size */
align = sec->base->sh.sh_addralign;
aligned_size = ((sec->base->sh.sh_size + align - 1) / align) * align;
if (src_offset != aligned_size)
ERROR("group size mismatch for section %s\n", sec->base->name);
if (!dest_offset) {
/* no changed or global functions referenced */
sec->status = SAME;
sec->base->status = SAME;
return;
}
/* overwrite with new relas list */
list_replace(&newrelas, &sec->relas);
/* include both rela and base sections */
sec->include = 1;
sec->base->include = 1;
/*
* Update text section data buf and size.
*
* The rela section's data buf and size will be regenerated in
* kpatch_rebuild_rela_section_data().
*/
sec->base->data->d_buf = dest;
sec->base->data->d_size = dest_offset;
}
void kpatch_include_debug_sections(struct kpatch_elf *kelf)
{
struct section *sec;
struct rela *rela, *saferela;
/* include all .debug_* sections */
list_for_each_entry(sec, &kelf->sections, list) {
if (is_debug_section(sec)) {
sec->include = 1;
if (!is_rela_section(sec))
sec->secsym->include = 1;
}
}
/*
* Go through the .rela.debug_ sections and strip entries
* referencing unchanged symbols
*/
list_for_each_entry(sec, &kelf->sections, list) {
if (!is_rela_section(sec) || !is_debug_section(sec))
continue;
list_for_each_entry_safe(rela, saferela, &sec->relas, list)
if (!rela->sym->sec->include)
list_del(&rela->list);
}
}
void kpatch_mark_ignored_sections(struct kpatch_elf *kelf)
{
struct section *sec, *strsec, *ignoresec;
struct rela *rela;
char *name;
sec = find_section_by_name(&kelf->sections, ".kpatch.ignore.sections");
if (!sec)
return;
list_for_each_entry(rela, &sec->rela->relas, list) {
strsec = rela->sym->sec;
strsec->status = CHANGED;
/*
* Include the string section here. This is because the
* KPATCH_IGNORE_SECTION() macro is passed a literal string
* by the patch author, resulting in a change to the string
* section. If we don't include it, then we will potentially
* get a "changed section not included" error in
* kpatch_verify_patchability() if no other function based change
* also changes the string section. We could try to exclude each
* literal string added to the section by KPATCH_IGNORE_SECTION()
* from the section data comparison, but this is a simpler way.
*/
strsec->include = 1;
name = strsec->data->d_buf + rela->addend;
ignoresec = find_section_by_name(&kelf->sections, name);
if (!ignoresec)
ERROR("expected ignored section");
log_normal("ignoring section %s\n", name);
ignoresec->ignore = 1;
if (ignoresec->twin)
ignoresec->twin->ignore = 1;
}
}
void kpatch_mark_ignored_sections_same(struct kpatch_elf *kelf)
{
struct section *sec;
struct symbol *sym;
list_for_each_entry(sec, &kelf->sections, list) {
if (!sec->ignore)
continue;
sec->status = SAME;
if (sec->secsym)
sec->secsym->status = SAME;
if (sec->rela)
sec->rela->status = SAME;
list_for_each_entry(sym, &kelf->symbols, list) {
if (sym->sec != sec)
continue;
sym->status = SAME;
}
}
}
void kpatch_mark_ignored_functions_same(struct kpatch_elf *kelf)
{
struct section *sec;
struct rela *rela;
sec = find_section_by_name(&kelf->sections, ".kpatch.ignore.functions");
if (!sec)
return;
list_for_each_entry(rela, &sec->rela->relas, list) {
if (!rela->sym->sec)
ERROR("expected bundled symbol");
if (rela->sym->type != STT_FUNC)
ERROR("expected function symbol");
log_normal("ignoring function %s\n", rela->sym->name);
if (rela->sym->status != CHANGED)
log_normal("NOTICE: no change detected in function %s, unnecessary KPATCH_IGNORE_FUNCTION()?\n", rela->sym->name);
rela->sym->status = SAME;
rela->sym->sec->status = SAME;
if (rela->sym->sec->secsym)
rela->sym->sec->secsym->status = SAME;
if (rela->sym->sec->rela)
rela->sym->sec->rela->status = SAME;
}
}
void kpatch_process_special_sections(struct kpatch_elf *kelf)
{
struct special_section *special;
struct section *sec;
struct symbol *sym;
struct rela *rela;
for (special = special_sections; special->name; special++) {
sec = find_section_by_name(&kelf->sections, special->name);
if (!sec)
continue;
sec = sec->rela;
if (!sec)
continue;
kpatch_regenerate_special_section(special, sec);
}
/*
* The following special sections don't have relas which reference
* non-included symbols, so their entire rela section can be included.
*/
list_for_each_entry(sec, &kelf->sections, list) {
if (strcmp(sec->name, ".altinstr_replacement"))
continue;
/* include base section */
sec->include = 1;
/* include all symbols in the section */
list_for_each_entry(sym, &kelf->symbols, list)
if (sym->sec == sec)
sym->include = 1;
/* include rela section */
if (sec->rela) {
sec->rela->include = 1;
/* include all symbols referenced by relas */
list_for_each_entry(rela, &sec->rela->relas, list)
rela->sym->include = 1;
}
}
/*
* The following special sections aren't supported, so make sure we
* don't ever try to include them. Otherwise the kernel will see the
* jump table during module loading and get confused. Generally it
* should be safe to exclude them, it just means that you can't modify
* jump labels and enable tracepoints in a patched function.
*/
list_for_each_entry(sec, &kelf->sections, list) {
if (strcmp(sec->name, "__jump_table") &&
strcmp(sec->name, "__tracepoints") &&
strcmp(sec->name, "__tracepoints_ptrs") &&
strcmp(sec->name, "__tracepoints_strings"))
continue;
sec->status = SAME;
if (sec->rela)
sec->rela->status = SAME;
}
}
void print_strtab(char *buf, size_t size)
{
int i;
for (i = 0; i < size; i++) {
if (buf[i] == 0)
printf("\\0");
else
printf("%c",buf[i]);
}
}
void kpatch_create_shstrtab(struct kpatch_elf *kelf)
{
struct section *shstrtab, *sec;
size_t size, offset, len;
char *buf;
shstrtab = find_section_by_name(&kelf->sections, ".shstrtab");
if (!shstrtab)
ERROR("find_section_by_name");
/* determine size of string table */
size = 1; /* for initial NULL terminator */
list_for_each_entry(sec, &kelf->sections, list)
size += strlen(sec->name) + 1; /* include NULL terminator */
/* allocate data buffer */
buf = malloc(size);
if (!buf)
ERROR("malloc");
memset(buf, 0, size);
/* populate string table and link with section header */
offset = 1;
list_for_each_entry(sec, &kelf->sections, list) {
len = strlen(sec->name) + 1;
sec->sh.sh_name = offset;
memcpy(buf + offset, sec->name, len);
offset += len;
}
if (offset != size)
ERROR("shstrtab size mismatch");
shstrtab->data->d_buf = buf;
shstrtab->data->d_size = size;
if (loglevel <= DEBUG) {
printf("shstrtab: ");
print_strtab(buf, size);
printf("\n");
list_for_each_entry(sec, &kelf->sections, list)
printf("%s @ shstrtab offset %d\n",
sec->name, sec->sh.sh_name);
}
}
void kpatch_create_strtab(struct kpatch_elf *kelf)
{
struct section *strtab;
struct symbol *sym;
size_t size = 0, offset = 0, len;
char *buf;
strtab = find_section_by_name(&kelf->sections, ".strtab");
if (!strtab)
ERROR("find_section_by_name");
/* determine size of string table */
list_for_each_entry(sym, &kelf->symbols, list) {
if (sym->type == STT_SECTION)
continue;
size += strlen(sym->name) + 1; /* include NULL terminator */
}
/* allocate data buffer */
buf = malloc(size);
if (!buf)
ERROR("malloc");
memset(buf, 0, size);
/* populate string table and link with section header */
list_for_each_entry(sym, &kelf->symbols, list) {
if (sym->type == STT_SECTION) {
sym->sym.st_name = 0;
continue;
}
len = strlen(sym->name) + 1;
sym->sym.st_name = offset;
memcpy(buf + offset, sym->name, len);
offset += len;
}
if (offset != size)
ERROR("shstrtab size mismatch");
strtab->data->d_buf = buf;
strtab->data->d_size = size;
if (loglevel <= DEBUG) {
printf("strtab: ");
print_strtab(buf, size);
printf("\n");
list_for_each_entry(sym, &kelf->symbols, list)
printf("%s @ strtab offset %d\n",
sym->name, sym->sym.st_name);
}
}
void kpatch_create_symtab(struct kpatch_elf *kelf)
{
struct section *symtab;
struct symbol *sym;
char *buf;
size_t size;
int nr = 0, offset = 0, nr_local = 0;
symtab = find_section_by_name(&kelf->sections, ".symtab");
if (!symtab)
ERROR("find_section_by_name");
/* count symbols */
list_for_each_entry(sym, &kelf->symbols, list)
nr++;
/* create new symtab buffer */
size = nr * symtab->sh.sh_entsize;
buf = malloc(size);
if (!buf)
ERROR("malloc");
memset(buf, 0, size);
offset = 0;
list_for_each_entry(sym, &kelf->symbols, list) {
memcpy(buf + offset, &sym->sym, symtab->sh.sh_entsize);
offset += symtab->sh.sh_entsize;
if (is_local_sym(sym))
nr_local++;
}
symtab->data->d_buf = buf;
symtab->data->d_size = size;
/* update symtab section header */
symtab->sh.sh_link = find_section_by_name(&kelf->sections, ".strtab")->index;
symtab->sh.sh_info = nr_local;
}
struct section *create_section_pair(struct kpatch_elf *kelf, char *name,
int entsize, int nr)
{
char *relaname;
struct section *sec, *relasec;
int size = entsize * nr;
relaname = malloc(strlen(name) + strlen(".rela") + 1);
if (!relaname)
ERROR("malloc");
strcpy(relaname, ".rela");
strcat(relaname, name);
/* allocate text section resources */
ALLOC_LINK(sec, &kelf->sections);
sec->name = name;
/* set data */
sec->data = malloc(sizeof(*sec->data));
if (!sec->data)
ERROR("malloc");
sec->data->d_buf = malloc(size);
if (!sec->data->d_buf)
ERROR("malloc");
sec->data->d_size = size;
sec->data->d_type = ELF_T_BYTE;
/* set section header */
sec->sh.sh_type = SHT_PROGBITS;
sec->sh.sh_entsize = entsize;
sec->sh.sh_addralign = 8;
sec->sh.sh_flags = SHF_ALLOC;
sec->sh.sh_size = size;
/* allocate rela section resources */
ALLOC_LINK(relasec, &kelf->sections);
relasec->name = relaname;
relasec->base = sec;
INIT_LIST_HEAD(&relasec->relas);
/* set data, buffers generated by kpatch_rebuild_rela_section_data() */
relasec->data = malloc(sizeof(*relasec->data));
if (!relasec->data)
ERROR("malloc");
/* set section header */
relasec->sh.sh_type = SHT_RELA;
relasec->sh.sh_entsize = sizeof(GElf_Rela);
relasec->sh.sh_addralign = 8;
/* set text rela section pointer */
sec->rela = relasec;
return sec;
}
void kpatch_create_patches_sections(struct kpatch_elf *kelf,
struct lookup_table *table, char *hint,
char *objname)
{
int nr, index, objname_offset;
struct section *sec, *relasec;
struct symbol *sym, *strsym;
struct rela *rela;
struct lookup_result result;
struct kpatch_patch_func *funcs;
/* count patched functions */
nr = 0;
list_for_each_entry(sym, &kelf->symbols, list)
if (sym->type == STT_FUNC && sym->status == CHANGED)
nr++;
/* create text/rela section pair */
sec = create_section_pair(kelf, ".kpatch.funcs", sizeof(*funcs), nr);
relasec = sec->rela;
funcs = sec->data->d_buf;
/* lookup strings symbol */
strsym = find_symbol_by_name(&kelf->symbols, ".kpatch.strings");
if (!strsym)
ERROR("can't find .kpatch.strings symbol");
/* add objname to strings */
objname_offset = offset_of_string(&kelf->strings, objname);
/* populate sections */
index = 0;
list_for_each_entry(sym, &kelf->symbols, list) {
if (sym->type == STT_FUNC && sym->status == CHANGED) {
if (sym->bind == STB_LOCAL) {
if (lookup_local_symbol(table, sym->name,
hint, &result))
ERROR("lookup_local_symbol %s (%s)",
sym->name, hint);
} else {
if(lookup_global_symbol(table, sym->name,
&result))
ERROR("lookup_global_symbol %s",
sym->name);
}
log_debug("lookup for %s @ 0x%016lx len %lu\n",
sym->name, result.value, result.size);
/* add entry in text section */
funcs[index].old_offset = result.value;
funcs[index].old_size = result.size;
funcs[index].new_size = sym->sym.st_size;
/*
* Add a relocation that will populate
* the funcs[index].new_addr field at
* module load time.
*/
ALLOC_LINK(rela, &relasec->relas);
rela->sym = sym;
rela->type = R_X86_64_64;
rela->addend = 0;
rela->offset = index * sizeof(*funcs);
/*
* Add a relocation that will populate
* the funcs[index].name field.
*/
ALLOC_LINK(rela, &relasec->relas);
rela->sym = strsym;
rela->type = R_X86_64_64;
rela->addend = offset_of_string(&kelf->strings, sym->name);
rela->offset = index * sizeof(*funcs) +
offsetof(struct kpatch_patch_func, name);
/*
* Add a relocation that will populate
* the funcs[index].objname field.
*/
ALLOC_LINK(rela, &relasec->relas);
rela->sym = strsym;
rela->type = R_X86_64_64;
rela->addend = objname_offset;
rela->offset = index * sizeof(*funcs) +
offsetof(struct kpatch_patch_func,objname);
index++;
}
}
/* sanity check, index should equal nr */
if (index != nr)
ERROR("size mismatch in funcs sections");
}
void kpatch_create_dynamic_rela_sections(struct kpatch_elf *kelf,
struct lookup_table *table, char *hint,
char *objname)
{
int nr, index, objname_offset;
struct section *sec, *sec2, *relasec;
struct rela *rela, *dynrela, *safe;
struct symbol *strsym;
struct lookup_result result;
struct kpatch_patch_dynrela *dynrelas;
int vmlinux, exported;
vmlinux = !strcmp(objname, "vmlinux");
/* count rela entries that need to be dynamic */
nr = 0;
list_for_each_entry(sec, &kelf->sections, list) {
if (!is_rela_section(sec))
continue;
if (!strcmp(sec->name, ".rela.kpatch.funcs"))
continue;
list_for_each_entry(rela, &sec->relas, list)
nr++; /* upper bound on number of dynrelas */
}
/* create text/rela section pair */
sec = create_section_pair(kelf, ".kpatch.dynrelas", sizeof(*dynrelas), nr);
relasec = sec->rela;
dynrelas = sec->data->d_buf;
/* lookup strings symbol */
strsym = find_symbol_by_name(&kelf->symbols, ".kpatch.strings");
if (!strsym)
ERROR("can't find .kpatch.strings symbol");
/* add objname to strings */
objname_offset = offset_of_string(&kelf->strings, objname);
/* populate sections */
index = 0;
list_for_each_entry(sec2, &kelf->sections, list) {
if (!is_rela_section(sec2))
continue;
if (!strcmp(sec2->name, ".rela.kpatch.patches") ||
!strcmp(sec2->name, ".rela.kpatch.dynrelas"))
continue;
list_for_each_entry_safe(rela, safe, &sec2->relas, list) {
if (rela->sym->sec)
continue;
exported = 0;
if (rela->sym->bind == STB_LOCAL) {
/* An unchanged local symbol */
if (lookup_local_symbol(table, rela->sym->name,
hint, &result))
ERROR("lookup_local_symbol %s (%s) needed for %s",
rela->sym->name, hint, sec2->base->name);
}
else if (vmlinux) {
/*
* We have a patch to vmlinux which references
* a global symbol. Use a normal rela for
* exported symbols and a dynrela otherwise.
*/
if (lookup_is_exported_symbol(table, rela->sym->name))
continue;
if (lookup_global_symbol(table, rela->sym->name,
&result))
ERROR("lookup_global_symbol failed for %s, needed for %s\n",
rela->sym->name,
sec2->base->name);
} else {
/*
* We have a patch to a module which references
* a global symbol.
*/
/*
* __fentry__ relas can't be converted to
* dynrelas because the ftrace module init code
* runs before the dynrela code can initialize
* them. __fentry__ is exported by the kernel,
* so leave it as a normal rela.
*/
if (!strcmp(rela->sym->name, "__fentry__"))
continue;
/*
* Try to find the symbol in the module being
* patched.
*/
if (lookup_global_symbol(table, rela->sym->name,
&result))
/*
* Not there, assume it's exported by
* another object.
*/
exported = 1;
}
log_debug("lookup for %s @ 0x%016lx len %lu\n",
rela->sym->name, result.value, result.size);
/* dest filed in by rela entry below */
if (vmlinux)
dynrelas[index].src = result.value;
else
/* for modules, src is discovered at runtime */
dynrelas[index].src = 0;
dynrelas[index].addend = rela->addend;
dynrelas[index].type = rela->type;
dynrelas[index].exported = exported;
/* add rela to fill in dest field */
ALLOC_LINK(dynrela, &relasec->relas);
if (sec2->base->sym)
dynrela->sym = sec2->base->sym;
else
dynrela->sym = sec2->base->secsym;
dynrela->type = R_X86_64_64;
dynrela->addend = rela->offset;
dynrela->offset = index * sizeof(*dynrelas);
/* add rela to fill in name field */
ALLOC_LINK(dynrela, &relasec->relas);
dynrela->sym = strsym;
dynrela->type = R_X86_64_64;
dynrela->addend = offset_of_string(&kelf->strings, rela->sym->name);
dynrela->offset = index * sizeof(*dynrelas) + offsetof(struct kpatch_patch_dynrela, name);
/* add rela to fill in objname field */
ALLOC_LINK(dynrela, &relasec->relas);
dynrela->sym = strsym;
dynrela->type = R_X86_64_64;
dynrela->addend = objname_offset;
dynrela->offset = index * sizeof(*dynrelas) +
offsetof(struct kpatch_patch_dynrela, objname);
list_del(&rela->list);
free(rela);
rela->sym->strip = 1;
index++;
}
}
/* set size to actual number of dynrelas */
sec->data->d_size = index * sizeof(struct kpatch_patch_dynrela);
sec->sh.sh_size = sec->data->d_size;
}
void kpatch_create_hooks_objname_rela(struct kpatch_elf *kelf, char *objname)
{
struct section *sec;
struct rela *rela;
struct symbol *strsym;
int objname_offset;
/* lookup strings symbol */
strsym = find_symbol_by_name(&kelf->symbols, ".kpatch.strings");
if (!strsym)
ERROR("can't find .kpatch.strings symbol");
/* add objname to strings */
objname_offset = offset_of_string(&kelf->strings, objname);
list_for_each_entry(sec, &kelf->sections, list) {
if (strcmp(sec->name, ".rela.kpatch.hooks.load") &&
strcmp(sec->name, ".rela.kpatch.hooks.unload"))
continue;
ALLOC_LINK(rela, &sec->relas);
rela->sym = strsym;
rela->type = R_X86_64_64;
rela->addend = objname_offset;
rela->offset = offsetof(struct kpatch_patch_hook, objname);
}
}
/*
* This function basically reimplements the functionality of the Linux
* recordmcount script, so that patched functions can be recognized by ftrace.
*
* TODO: Eventually we can modify recordmount so that it recognizes our bundled
* sections as valid and does this work for us.
*/
void kpatch_create_mcount_sections(struct kpatch_elf *kelf)
{
int nr, index;
struct section *sec, *relasec;
struct symbol *sym;
struct rela *rela;
void **funcs, *newdata;
unsigned char *insn;
nr = 0;
list_for_each_entry(sym, &kelf->symbols, list)
if (sym->type == STT_FUNC && sym->status != SAME)
nr++;
/* create text/rela section pair */
sec = create_section_pair(kelf, "__mcount_loc", sizeof(*funcs), nr);
relasec = sec->rela;
funcs = sec->data->d_buf;
/* populate sections */
index = 0;
list_for_each_entry(sym, &kelf->symbols, list) {
if (sym->type != STT_FUNC || sym->status == SAME)
continue;
/* add rela in .rela__mcount_loc to fill in function pointer */
ALLOC_LINK(rela, &relasec->relas);
rela->sym = sym;
rela->type = R_X86_64_64;
rela->addend = 0;
rela->offset = index * sizeof(*funcs);
/*
* Modify the first instruction of the function to "callq
* __fentry__" so that ftrace will be happy.
*/
newdata = malloc(sym->sec->data->d_size);
memcpy(newdata, sym->sec->data->d_buf, sym->sec->data->d_size);
sym->sec->data->d_buf = newdata;
insn = newdata;
if (insn[0] != 0xf)
ERROR("bad first instruction in %s", sym->name);
insn[0] = 0xe8;
insn[1] = 0;
insn[2] = 0;
insn[3] = 0;
insn[4] = 0;
rela = list_first_entry(&sym->sec->rela->relas, struct rela,
list);
if (rela->type != R_X86_64_NONE ||
strcmp(rela->sym->name, "__fentry__"))
ERROR("bad first rela in %s", sym->sec->rela->name);
rela->type = R_X86_64_PC32;
index++;
}
/* sanity check, index should equal nr */
if (index != nr)
ERROR("size mismatch in funcs sections");
}
/*
* This function strips out symbols that were referenced by changed rela
* sections, but the rela entries that referenced them were converted to
* dynrelas and are no longer needed.
*/
void kpatch_strip_unneeded_syms(struct kpatch_elf *kelf,
struct lookup_table *table)
{
struct symbol *sym, *safe;
list_for_each_entry_safe(sym, safe, &kelf->symbols, list) {
if (sym->strip) {
list_del(&sym->list);
free(sym);
}
}
}
void kpatch_create_strings_elements(struct kpatch_elf *kelf)
{
struct section *sec;
struct symbol *sym;
/* create .kpatch.strings */
/* allocate section resources */
ALLOC_LINK(sec, &kelf->sections);
sec->name = ".kpatch.strings";
/* set data */
sec->data = malloc(sizeof(*sec->data));
if (!sec->data)
ERROR("malloc");
sec->data->d_type = ELF_T_BYTE;
/* set section header */
sec->sh.sh_type = SHT_PROGBITS;
sec->sh.sh_entsize = 1;
sec->sh.sh_addralign = 1;
sec->sh.sh_flags = SHF_ALLOC;
/* create .kpatch.strings section symbol (reuse sym variable) */
ALLOC_LINK(sym, &kelf->symbols);
sym->sec = sec;
sym->sym.st_info = GELF_ST_INFO(STB_LOCAL, STT_SECTION);
sym->type = STT_SECTION;
sym->bind = STB_LOCAL;
sym->name = ".kpatch.strings";
}
void kpatch_build_strings_section_data(struct kpatch_elf *kelf)
{
struct string *string;
struct section *sec;
int size;
char *strtab;
sec = find_section_by_name(&kelf->sections, ".kpatch.strings");
if (!sec)
ERROR("can't find .kpatch.strings");
/* determine size */
size = 0;
list_for_each_entry(string, &kelf->strings, list)
size += strlen(string->name) + 1;
/* allocate section resources */
strtab = malloc(size);
if (!strtab)
ERROR("malloc");
sec->data->d_buf = strtab;
sec->data->d_size = size;
/* populate strings section data */
list_for_each_entry(string, &kelf->strings, list) {
strcpy(strtab, string->name);
strtab += strlen(string->name) + 1;
}
}
void kpatch_rebuild_rela_section_data(struct section *sec)
{
struct rela *rela;
int nr = 0, index = 0, size;
GElf_Rela *relas;
list_for_each_entry(rela, &sec->relas, list)
nr++;
size = nr * sizeof(*relas);
relas = malloc(size);
if (!relas)
ERROR("malloc");
sec->data->d_buf = relas;
sec->data->d_size = size;
/* d_type remains ELF_T_RELA */
sec->sh.sh_size = size;
list_for_each_entry(rela, &sec->relas, list) {
relas[index].r_offset = rela->offset;
relas[index].r_addend = rela->addend;
relas[index].r_info = GELF_R_INFO(rela->sym->index, rela->type);
index++;
}
/* sanity check, index should equal nr */
if (index != nr)
ERROR("size mismatch in rebuilt rela section");
}
void kpatch_write_output_elf(struct kpatch_elf *kelf, Elf *elf, char *outfile)
{
int fd;
struct section *sec;
Elf *elfout;
GElf_Ehdr eh, ehout;
Elf_Scn *scn;
Elf_Data *data;
GElf_Shdr sh;
/* TODO make this argv */
fd = creat(outfile, 0777);
if (fd == -1)
ERROR("creat");
elfout = elf_begin(fd, ELF_C_WRITE, NULL);
if (!elfout)
ERROR("elf_begin");
if (!gelf_newehdr(elfout, gelf_getclass(kelf->elf)))
ERROR("gelf_newehdr");
if (!gelf_getehdr(elfout, &ehout))
ERROR("gelf_getehdr");
if (!gelf_getehdr(elf, &eh))
ERROR("gelf_getehdr");
memset(&ehout, 0, sizeof(ehout));
ehout.e_ident[EI_DATA] = eh.e_ident[EI_DATA];
ehout.e_machine = eh.e_machine;
ehout.e_type = eh.e_type;
ehout.e_version = EV_CURRENT;
ehout.e_shstrndx = find_section_by_name(&kelf->sections, ".shstrtab")->index;
/* add changed sections */
list_for_each_entry(sec, &kelf->sections, list) {
scn = elf_newscn(elfout);
if (!scn)
ERROR("elf_newscn");
data = elf_newdata(scn);
if (!data)
ERROR("elf_newdata");
if (!elf_flagdata(data, ELF_C_SET, ELF_F_DIRTY))
ERROR("elf_flagdata");
data->d_type = sec->data->d_type;
data->d_buf = sec->data->d_buf;
data->d_size = sec->data->d_size;
if(!gelf_getshdr(scn, &sh))
ERROR("gelf_getshdr");
sh = sec->sh;
if (!gelf_update_shdr(scn, &sh))
ERROR("gelf_update_shdr");
}
if (!gelf_update_ehdr(elfout, &ehout))
ERROR("gelf_update_ehdr");
if (elf_update(elfout, ELF_C_WRITE) < 0) {
printf("%s\n",elf_errmsg(-1));
ERROR("elf_update");
}
}
struct arguments {
char *args[4];
int debug;
};
static char args_doc[] = "original.o patched.o kernel-object output.o";
static struct argp_option options[] = {
{"debug", 'd', 0, 0, "Show debug output" },
{ 0 }
};
static error_t parse_opt (int key, char *arg, struct argp_state *state)
{
/* Get the input argument from argp_parse, which we
know is a pointer to our arguments structure. */
struct arguments *arguments = state->input;
switch (key)
{
case 'd':
arguments->debug = 1;
break;
case ARGP_KEY_ARG:
if (state->arg_num >= 4)
/* Too many arguments. */
argp_usage (state);
arguments->args[state->arg_num] = arg;
break;
case ARGP_KEY_END:
if (state->arg_num < 4)
/* Not enough arguments. */
argp_usage (state);
break;
default:
return ARGP_ERR_UNKNOWN;
}
return 0;
}
static struct argp argp = { options, parse_opt, args_doc, 0 };
/*
* While this is a one-shot program without a lot of proper cleanup in case
* of an error, this function serves a debugging purpose: to break down and
* zero data structures we shouldn't be accessing anymore. This should
* help cause an immediate and obvious issue when a logic error leads to
* accessing data that is not intended to be accessed past a particular point.
*/
void kpatch_elf_teardown(struct kpatch_elf *kelf)
{
struct section *sec, *safesec;
struct symbol *sym, *safesym;
struct rela *rela, *saferela;
list_for_each_entry_safe(sec, safesec, &kelf->sections, list) {
if (is_rela_section(sec)) {
list_for_each_entry_safe(rela, saferela, &sec->relas, list) {
memset(rela, 0, sizeof(*rela));
free(rela);
}
memset(sec, 0, sizeof(*sec));
free(sec);
}
}
list_for_each_entry_safe(sym, safesym, &kelf->symbols, list) {
memset(sym, 0, sizeof(*sym));
free(sym);
}
INIT_LIST_HEAD(&kelf->sections);
INIT_LIST_HEAD(&kelf->symbols);
}
void kpatch_elf_free(struct kpatch_elf *kelf)
{
elf_end(kelf->elf);
close(kelf->fd);
memset(kelf, 0, sizeof(*kelf));
free(kelf);
}
int main(int argc, char *argv[])
{
struct kpatch_elf *kelf_base, *kelf_patched, *kelf_out;
struct arguments arguments;
int num_changed;
struct lookup_table *lookup;
struct section *sec, *symtab;
struct symbol *sym;
char *hint = NULL, *name, *pos;
arguments.debug = 0;
argp_parse (&argp, argc, argv, 0, 0, &arguments);
if (arguments.debug)
loglevel = DEBUG;
elf_version(EV_CURRENT);
objname = basename(arguments.args[0]);
kelf_base = kpatch_elf_open(arguments.args[0]);
kelf_patched = kpatch_elf_open(arguments.args[1]);
kpatch_compare_elf_headers(kelf_base->elf, kelf_patched->elf);
kpatch_check_program_headers(kelf_base->elf);
kpatch_check_program_headers(kelf_patched->elf);
kpatch_replace_sections_syms(kelf_base);
kpatch_replace_sections_syms(kelf_patched);
kpatch_rename_mangled_functions(kelf_base, kelf_patched);
kpatch_correlate_elfs(kelf_base, kelf_patched);
kpatch_correlate_static_local_variables(kelf_base, kelf_patched);
/*
* After this point, we don't care about kelf_base anymore.
* We access its sections via the twin pointers in the
* section, symbol, and rela lists of kelf_patched.
*/
kpatch_mark_ignored_sections(kelf_patched);
kpatch_compare_correlated_elements(kelf_patched);
kpatch_elf_teardown(kelf_base);
kpatch_elf_free(kelf_base);
kpatch_mark_ignored_functions_same(kelf_patched);
kpatch_mark_ignored_sections_same(kelf_patched);
kpatch_process_special_sections(kelf_patched);
kpatch_include_standard_elements(kelf_patched);
num_changed = kpatch_include_changed_functions(kelf_patched);
kpatch_include_debug_sections(kelf_patched);
kpatch_include_hook_elements(kelf_patched);
kpatch_include_force_elements(kelf_patched);
kpatch_dump_kelf(kelf_patched);
kpatch_verify_patchability(kelf_patched);
if (!num_changed) {
log_normal("no changed functions were found\n");
return 3; /* 1 is ERROR, 2 is DIFF_FATAL */
}
/* this is destructive to kelf_patched */
kpatch_migrate_included_elements(kelf_patched, &kelf_out);
/*
* Teardown kelf_patched since we shouldn't access sections or symbols
* through it anymore. Don't free however, since our section and symbol
* name fields still point to strings in the Elf object owned by
* kpatch_patched.
*/
kpatch_elf_teardown(kelf_patched);
list_for_each_entry(sym, &kelf_out->symbols, list) {
if (sym->type == STT_FILE) {
hint = sym->name;
break;
}
}
if (!hint)
ERROR("FILE symbol not found in output. Stripped?\n");
/* create symbol lookup table */
lookup = lookup_open(arguments.args[2]);
/* extract module name (destructive to arguments.modulefile) */
name = basename(arguments.args[2]);
if (!strncmp(name, "vmlinux-", 8))
name = "vmlinux";
else {
pos = strchr(name,'.');
if (pos) {
/* kernel module */
*pos = '\0';
pos = name;
while ((pos = strchr(pos, '-')))
*pos++ = '_';
}
}
/* create strings, patches, and dynrelas sections */
kpatch_create_strings_elements(kelf_out);
kpatch_create_patches_sections(kelf_out, lookup, hint, name);
kpatch_create_dynamic_rela_sections(kelf_out, lookup, hint, name);
kpatch_create_hooks_objname_rela(kelf_out, name);
kpatch_build_strings_section_data(kelf_out);
kpatch_create_mcount_sections(kelf_out);
/*
* At this point, the set of output sections and symbols is
* finalized. Reorder the symbols into linker-compliant
* order and index all the symbols and sections. After the
* indexes have been established, update index data
* throughout the structure.
*/
kpatch_reorder_symbols(kelf_out);
kpatch_strip_unneeded_syms(kelf_out, lookup);
kpatch_reindex_elements(kelf_out);
/*
* Update rela section headers and rebuild the rela section data
* buffers from the relas lists.
*/
symtab = find_section_by_name(&kelf_out->sections, ".symtab");
list_for_each_entry(sec, &kelf_out->sections, list) {
if (!is_rela_section(sec))
continue;
sec->sh.sh_link = symtab->index;
sec->sh.sh_info = sec->base->index;
kpatch_rebuild_rela_section_data(sec);
}
kpatch_create_shstrtab(kelf_out);
kpatch_create_strtab(kelf_out);
kpatch_create_symtab(kelf_out);
kpatch_dump_kelf(kelf_out);
kpatch_write_output_elf(kelf_out, kelf_patched->elf, arguments.args[3]);
kpatch_elf_free(kelf_patched);
kpatch_elf_teardown(kelf_out);
kpatch_elf_free(kelf_out);
return 0;
}
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