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SubjectRe: [PATCH 2/2] objtool: Add support for relocations without addends
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Hi Matt,

On 5/29/20 10:01 PM, Matt Helsley wrote:
> Currently objtool only collects information about relocations with
> addends. In recordmcount, which we are about to merge into objtool,
> some supported architectures do not use rela relocations.
>
> Signed-off-by: Matt Helsley <mhelsley@vmware.com>
> ---
> tools/objtool/elf.c | 146 +++++++++++++++++++++++++++++++++++-----
> tools/objtool/elf.h | 7 +-
> tools/objtool/orc_gen.c | 2 +-
> 3 files changed, 135 insertions(+), 20 deletions(-)
>
> diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
> index c21e8417637b..5034918494b6 100644
> --- a/tools/objtool/elf.c
> +++ b/tools/objtool/elf.c
> @@ -490,6 +490,32 @@ void elf_add_reloc(struct elf *elf, struct reloc *reloc)
> elf_hash_add(elf->reloc_hash, &reloc->hash, reloc_hash(reloc));
> }
>
> +static int read_rel_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
> +{
> + if (!gelf_getrel(sec->data, i, &reloc->rel)) {
> + WARN_ELF("gelf_getrel");
> + return -1;
> + }
> + reloc->type = GELF_R_TYPE(reloc->rel.r_info);
> + reloc->addend = 0;
> + reloc->offset = reloc->rel.r_offset;
> + *symndx = GELF_R_SYM(reloc->rel.r_info);
> + return 0;
> +}
> +
> +static int read_rela_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
> +{
> + if (!gelf_getrela(sec->data, i, &reloc->rela)) {
> + WARN_ELF("gelf_getrela");
> + return -1;
> + }
> + reloc->type = GELF_R_TYPE(reloc->rela.r_info);
> + reloc->addend = reloc->rela.r_addend;
> + reloc->offset = reloc->rela.r_offset;
> + *symndx = GELF_R_SYM(reloc->rela.r_info);
> + return 0;
> +}
> +
> static int read_relocs(struct elf *elf)
> {
> struct section *sec;
> @@ -499,7 +525,8 @@ static int read_relocs(struct elf *elf)
> unsigned long nr_reloc, max_reloc = 0, tot_reloc = 0;
>
> list_for_each_entry(sec, &elf->sections, list) {
> - if (sec->sh.sh_type != SHT_RELA)
> + if ((sec->sh.sh_type != SHT_RELA) &&
> + (sec->sh.sh_type != SHT_REL))
> continue;
>
> sec->base = find_section_by_index(elf, sec->sh.sh_info);
> @@ -519,16 +546,17 @@ static int read_relocs(struct elf *elf)
> return -1;
> }
> memset(reloc, 0, sizeof(*reloc));
> -
> - if (!gelf_getrela(sec->data, i, &reloc->rela)) {
> - WARN_ELF("gelf_getrela");
> - return -1;
> + switch(sec->sh.sh_type) {
> + case SHT_REL:
> + if (read_rel_reloc(sec, i, reloc, &symndx))
> + return -1;
> + break;
> + case SHT_RELA:
> + if (read_rela_reloc(sec, i, reloc, &symndx))
> + return -1;
> + break;
> + default: return -1;
> }
> -
> - reloc->type = GELF_R_TYPE(reloc->rela.r_info);
> - reloc->addend = reloc->rela.r_addend;
> - reloc->offset = reloc->rela.r_offset;
> - symndx = GELF_R_SYM(reloc->rela.r_info);
> reloc->sym = find_symbol_by_index(elf, symndx);
> reloc->sec = sec;
> if (!reloc->sym) {
> @@ -716,7 +744,38 @@ struct section *elf_create_section(struct elf *elf, const char *name,
> return sec;
> }
>
> -struct section *elf_create_reloc_section(struct elf *elf, struct section *base)
> +static struct section *elf_create_rel_reloc_section(struct elf *elf, struct section *base)
> +{
> + char *relocname;
> + struct section *sec;
> +
> + relocname = malloc(strlen(base->name) + strlen(".rel") + 1);
> + if (!relocname) {
> + perror("malloc");
> + return NULL;
> + }
> + strcpy(relocname, ".rel");
> + strcat(relocname, base->name);
> +
> + sec = elf_create_section(elf, relocname, sizeof(GElf_Rel), 0);
> + free(relocname);
> + if (!sec)
> + return NULL;
> +
> + base->reloc = sec;
> + sec->base = base;
> +
> + sec->sh.sh_type = SHT_REL;
> + sec->sh.sh_addralign = 8;
> + sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
> + sec->sh.sh_info = base->idx;
> + sec->sh.sh_flags = SHF_INFO_LINK;
> +
> + return sec;
> +}
> +
> +

Nit: Extra new line.

Otherwise:

Reviewed-by: Julien Thierry <jthierry@redhat.com>

--
Julien Thierry

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