RepoMirrors/kpatch
1
0
Fork 0
mirror of https://github.com/dynup/kpatch synced 2025-05-04 17:07:56 +00:00
Code Issues Packages Projects Releases Wiki Activity

Merge pull request #133 from spartacus06/bugtable

Browse Source 
Add support for bug table and data in .bss sections
This commit is contained in:
Josh Poimboeuf 2014-04-22 15:30:46 -05:00
commit 2e607644e1
1 changed files with 91 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

93
kpatch-build/create-diff-object.c
View File

@ -336,6 +336,11 @@ int is_bundleable(struct symbol *sym)
!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;
}
@ -966,6 +971,88 @@ void kpatch_write_inventory_file(struct kpatch_elf *kelf, char *outfile)
fclose(out);
}
/*
* The format of section __bug_table is a table of struct bug_entry. Each
* bug_entry has three fields:
* - relocated address of instruction pointer at BUG
* - relocated address of string with filename
* - line number of the BUG
*
* Therefore, .rela__bug_table has two relocations per entry. The first
* relocation is that of the instruction pointer at the BUG. The second is the
* pointer to the filename string in .rodata.str1.1. These two related
* relocations we will call a "pair".
*
* This function goes through .rela__bug_table and finds pairs the refer to
* functions that have been marked as changed. If one is found, that pair is
* copied into the new version of the .rela__bug_table section. If no pairs
* are found, the bug table (both the __bug_table and .rela__bug_table
* sections) are considered unchanged and not copied into the final output.
*
* The __bug_table section is not modified and therefore will contains "blank"
* bug_entry slots i.e. ones that do not get relocated and therefore the IP
* fields are zero. While this wastes space, it doesn't hurt anything and
* keeps the code cleaner by not having to regenerate the __bug_table section
* as well.
*/
void kpatch_regenerate_bug_table_rela_section(struct kpatch_elf *kelf)
{
struct section *sec;
struct table table;
struct rela *rela, *dstrela;
int i, nr = 0, copynext = 0;
sec = find_section_by_name(&kelf->sections, ".rela__bug_table");
if (!sec)
return;
/* alloc buffer of original size (probably won't use it all) */
alloc_table(&table, sizeof(struct rela), sec->relas.nr);
dstrela = table.data;
for_each_rela(i, rela, &sec->relas) {
if (i % 2) { /* filename reloc */
if (!copynext)
continue;
rela->sym->include = 1;
rela->sym->sec->include = 1;
*dstrela++ = *rela;
nr++;
copynext = 0;
}
else if (rela->sym->sec->status != SAME) { /* IP reloc */
log_debug("new/changed symbol %s found in bug table\n",
rela->sym->name);
/* copy BOTH relocs for this bug_entry */
*dstrela++ = *rela;
nr++;
/* tell the next loop to copy the filename reloc */
copynext = 1;
}
}
if (!nr) {
/* no changed functions referenced by bug table */
sec->status = SAME;
sec->base->status = SAME;
return;
}
/* overwrite with new relas table */
table.nr = nr;
sec->relas = table;
sec->include = 1;
sec->base->include = 1;
/*
* Adjust d_size but not d_buf. d_buf is overwritten in
* kpatch_create_rela_section() from the relas table. No
* point in regen'ing the buffer here just to be discarded
* later.
*/
sec->data->d_size = sec->sh.sh_entsize * nr;
}
void kpatch_create_rela_section(struct section *sec, int link)
{
struct rela *rela;
@ -974,7 +1061,7 @@ void kpatch_create_rela_section(struct section *sec, int link)
size_t size;
/* create new rela data buffer */
size = sec->sh.sh_size;
size = sec->data->d_size;
buf = malloc(size);
if (!buf)
ERROR("malloc");
@ -983,7 +1070,8 @@ void kpatch_create_rela_section(struct section *sec, int link)
/* reindex and copy into buffer */
for_each_rela(i, rela, &sec->relas) {
if (!rela->sym || !rela->sym->twino)
ERROR("expected rela symbol");
ERROR("expected rela symbol in rela section %s entry %d",
sec->name, i);
symndx = rela->sym->twino->index;
type = GELF_R_TYPE(rela->rela.r_info);
rela->rela.r_info = GELF_R_INFO(symndx, type);
@ -1318,6 +1406,7 @@ int main(int argc, char *argv[])
* in vmlinux can be linked to.
*/
kpatch_replace_sections_syms(kelf_patched);
kpatch_regenerate_bug_table_rela_section(kelf_patched);
kpatch_include_standard_sections(kelf_patched);
if (!kpatch_include_changed_functions(kelf_patched)) {