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create-klp-module: get rid of redundant kpatch_relocation.offset field 

kpatch_relocation's 'dest' addend and 'offset' fields are redundant.  In
fact, the 'offset' field isn't always accurate because it doesn't have a
relocation, so its value doesn't adjust when multiple .o files are
combined.  Just use the 'dest' addend instead.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
This commit is contained in:
Josh Poimboeuf 2017-11-08 13:53:17 -06:00
parent f0518ef58a
commit c6c153431f
3 changed files with 11 additions and 45 deletions
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1
kpatch-build/create-diff-object.c
View File

@ -2517,7 +2517,6 @@ static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf,
krelas[index].addend = rela->addend;
krelas[index].type = rela->type;
krelas[index].external = external;
krelas[index].offset = rela->offset;
/* add rela to fill in krelas[index].dest field */
ALLOC_LINK(rela2, &krela_sec->rela->relas);

54
kpatch-build/create-klp-module.c
View File

@ -160,7 +160,7 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
struct symbol *sym, *dest;
struct rela *rela;
char *objname;
int nr, index, offset, toc_offset;
int nr, index, offset, dest_off;
krelas = krelasec->data->d_buf;
nr = krelasec->data->d_size / sizeof(*krelas);
@ -168,48 +168,16 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
for (index = 0; index < nr; index++) {
offset = index * sizeof(*krelas);
/* Get the base section to which the rela applies */
/* Get the rela dest sym + offset */
rela = find_rela_by_offset(krelasec->rela,
offset + offsetof(struct kpatch_relocation, dest));
if (!rela)
ERROR("find_rela_by_offset");
/*
* Patched file:
* Relocation section '.rela.toc' at offset 0x46358 contains 60 entries:
* Offset Info Type Symbol's Value Symbol's Name + Addend
* 0000000000000000 000001ee00000026 R_PPC64_ADDR64 0000000000000000 jiffies + 0
* 0000000000000008 0000009400000026 R_PPC64_ADDR64 0000000000000000 __tracepoints + 0
* 0000000000000010 000001db00000026 R_PPC64_ADDR64 0000000000000000 __cpu_online_mask + 0
* 0000000000000018 0000009c00000026 R_PPC64_ADDR64 0000000000000000 .data..percpu + 0
* 0000000000000020 000001ac00000026 R_PPC64_ADDR64 0000000000000000 __per_cpu_offset + 0
* 0000000000000028 0000006900000026 R_PPC64_ADDR64 0000000000000000 .rodata.str1.8 + 0
* [...]
*
* Output file:
* Relocation section '.rela.toc' at offset 0x1270 contains 58 entries:
* Offset Info Type Symbol's Value Symbol's Name + Addend
* 0000000000000000 0000000700000026 R_PPC64_ADDR64 0000000000000000 .data + 0
* 0000000000000008 0000003c00000026 R_PPC64_ADDR64 0000000000000000 __kpatch_funcs + 0
* 0000000000000010 0000005300000026 R_PPC64_ADDR64 0000000000000000 kmalloc_caches + 0
* 0000000000000018 0000001100000026 R_PPC64_ADDR64 0000000000000000 .rodata.str1.8 + 0
* 0000000000000020 0000001600000026 R_PPC64_ADDR64 0000000000000000 .bss + 0
* 0000000000000028 0000004200000026 R_PPC64_ADDR64 0000000000000038 __kpatch_funcs_end + 0
* 0000000000000030 0000003400000026 R_PPC64_ADDR64 0000000000000000 __this_module + 0
* 0000000000000038 0000004d00000026 R_PPC64_ADDR64 0000000000000000 jiffies + 0
* 0000000000000048 0000004500000026 R_PPC64_ADDR64 0000000000000000 __cpu_online_mask + 0
* 0000000000000058 0000003900000026 R_PPC64_ADDR64 0000000000000000 __per_cpu_offset + 0
* [...]
*
* On ppc64le, when .o files are linked together, the .toc
* entries might get re-arranged. Capture the new .toc rela
* offset value, which is used below to set the rela->addend.
*/
toc_offset = rela->addend;
dest = rela->sym;
dest_off = rela->addend;
/* Get the name of the object the rela belongs to */
/* Get the name of the object the dest belongs to */
rela = find_rela_by_offset(krelasec->rela,
offset + offsetof(struct kpatch_relocation, objname));
if (!rela)
@ -219,31 +187,31 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
if (!objname)
ERROR("strdup");
/* Get the corresponding .kpatch.symbol entry */
/* Get the .kpatch.symbol entry for the rela src */
rela = find_rela_by_offset(krelasec->rela,
offset + offsetof(struct kpatch_relocation, ksym));
if (!rela)
ERROR("find_rela_by_offset");
/* Create (or find) a real symbol out of the .kpatch.symbol entry */
/* Create (or find) a klp symbol from the rela src entry */
sym = find_or_add_ksym_to_symbols(kelf, ksymsec, strings, rela->addend);
if (!sym)
ERROR("error finding or adding ksym to symtab");
/* Create (or find) the .klp.rela. section for this dest sec and object */
/* Create (or find) the .klp.rela. section for the dest sec and object */
klp_relasec = find_or_add_klp_relasec(kelf, dest->sec, objname);
if (!klp_relasec)
ERROR("error finding or adding klp relasec");
/* Add the rela to the .klp.rela. section */
/* Add the klp rela to the .klp.rela. section */
ALLOC_LINK(rela, &klp_relasec->relas);
rela->type = krelas[index].type;
rela->sym = sym;
rela->addend = krelas[index].addend;
rela->type = krelas[index].type;
if (!strcmp(dest->sec->name, ".toc"))
rela->offset = toc_offset;
rela->offset = dest_off;
else
rela->offset = krelas[index].offset + dest->sym.st_value;
rela->offset = dest_off + dest->sym.st_value;
}
}

1
kpatch-build/kpatch-intermediate.h
View File

@ -36,7 +36,6 @@ struct kpatch_relocation {
unsigned long dest;
unsigned int type;
int addend;
int offset;
int external;
char *objname; /* object to which this rela applies to */
struct kpatch_symbol *ksym;