RepoMirrors
/
kpatch
mirror of https://github.com/dynup/kpatch
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

kpatch-build: do symbol/section bundling in create-diff-object 

kpatch-elf.c is used by binaries other than create-diff-object, but
create-diff-object is the only one that cares about "bundling".  Move
the bundling to create-diff-object.

Fixes #700.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
This commit is contained in:
Josh Poimboeuf 2017-09-20 11:55:01 -05:00
parent 5888f316e6
commit b72027c44e
2 changed files with 100 additions and 82 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

99
kpatch-build/create-diff-object.c
View File

@ -81,6 +81,102 @@ struct special_section {
* Functions
* **********/
static 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, ".rodata.",8) &&
!strcmp(sym->sec->name + 8, 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;
}
#ifdef __powerpc__
/* Symbol st_others value for powerpc */
#define STO_PPC64_LOCAL_BIT 5
#define STO_PPC64_LOCAL_MASK (7 << STO_PPC64_LOCAL_BIT)
#define PPC64_LOCAL_ENTRY_OFFSET(other) \
(((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2)
/*
* On ppc64le, the function prologue generated by GCC 6+ has the sequence:
*
* .globl my_func
* .type my_func, @function
* .quad .TOC.-my_func
* my_func:
* .reloc ., R_PPC64_ENTRY ; optional
* ld r2,-8(r12)
* add r2,r2,r12
* .localentry my_func, .-my_func
*
* my_func is the global entry point, which, when called, sets up the TOC.
* .localentry is the local entry point, for calls to the function from within
* the object file. The local entry point is 8 bytes after the global entry
* point.
*/
static int is_localentry_sym(struct symbol *sym)
{
if (sym->type != STT_FUNC || sym->sym.st_shndx == SHN_UNDEF)
return 0;
if (sym->sym.st_value != 0x8)
return 0;
if (!PPC64_LOCAL_ENTRY_OFFSET(sym->sym.st_other))
return 0;
return 1;
}
#else
static int is_localentry_sym(struct symbol *sym)
{
return 0;
}
#endif
/*
* When compiling with -ffunction-sections and -fdata-sections, almost every
* symbol gets its own dedicated section. We call such symbols "bundled"
* symbols. They're indicated by "sym->sec->sym == sym".
*/
static void kpatch_bundle_symbols(struct kpatch_elf *kelf)
{
struct symbol *sym;
list_for_each_entry(sym, &kelf->symbols, list) {
if (is_bundleable(sym)) {
if (sym->sym.st_value != 0 && !is_localentry_sym(sym)) {
ERROR("symbol %s at offset %lu within section %s, expected 0",
sym->name, sym->sym.st_value,
sym->sec->name);
}
sym->sec->sym = sym;
}
}
}
/*
* This function detects whether the given symbol is a "special" static local
* variable (for lack of a better term).
@ -2713,6 +2809,9 @@ int main(int argc, char *argv[])
kelf_base = kpatch_elf_open(arguments.args[0]);
kelf_patched = kpatch_elf_open(arguments.args[1]);
kpatch_bundle_symbols(kelf_base);
kpatch_bundle_symbols(kelf_patched);
kpatch_compare_elf_headers(kelf_base->elf, kelf_patched->elf);
kpatch_check_program_headers(kelf_base->elf);
kpatch_check_program_headers(kelf_patched->elf);

83
kpatch-build/kpatch-elf.c
View File

@ -76,46 +76,6 @@ int is_debug_section(struct section *sec)
!strncmp(name, ".eh_frame", 9);
}
#ifdef __powerpc__
/* Symbol st_others value for powerpc */
#define STO_PPC64_LOCAL_BIT 5
#define STO_PPC64_LOCAL_MASK (7 << STO_PPC64_LOCAL_BIT)
#define PPC64_LOCAL_ENTRY_OFFSET(other) \
(((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2)
/*
* On ppc64le, the function prologue generated by GCC 6+ has the sequence:
*
* .globl my_func
* .type my_func, @function
* .quad .TOC.-my_func
* my_func:
* .reloc ., R_PPC64_ENTRY ; optional
* ld r2,-8(r12)
* add r2,r2,r12
* .localentry my_func, .-my_func
*
* my_func is the global entry point, which, when called, sets up the TOC.
* .localentry is the local entry point, for calls to the function from within
* the object file. The local entry point is 8 bytes after the global entry
* point.
*/
static int is_localentry_sym(struct symbol *sym)
{
if (sym->type != STT_FUNC || sym->sym.st_shndx == SHN_UNDEF)
return 0;
if (sym->sym.st_value != 0x8)
return 0;
if (!PPC64_LOCAL_ENTRY_OFFSET(sym->sym.st_other))
return 0;
return 1;
}
#endif
struct section *find_section_by_index(struct list_head *list, unsigned int index)
{
struct section *sec;
@ -299,36 +259,6 @@ void kpatch_create_section_list(struct kpatch_elf *kelf)
ERROR("expected NULL");
}
static 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, ".rodata.",8) &&
!strcmp(sym->sec->name + 8, 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;
@ -367,18 +297,7 @@ void kpatch_create_symbol_list(struct kpatch_elf *kelf)
ERROR("couldn't find section for symbol %s\n",
sym->name);
if (is_bundleable(sym)) {
if (sym->sym.st_value != 0) {
#ifdef __powerpc__
if (!is_localentry_sym(sym))
#endif
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) {
if (sym->type == STT_SECTION) {
sym->sec->secsym = sym;
/* use the section name as the symbol name */
sym->name = sym->sec->name;