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SubjectRe: [RFC PATCH v3 03/12] objtool: Use target file class size instead of a compiled constant
Date


Le 24/06/2022 à 20:32, Sathvika Vasireddy a écrit :
> From: Christophe Leroy <christophe.leroy@csgroup.eu>
>
> In order to allow using objtool on cross-built kernels,
> determine size of long from elf data instead of using
> sizeof(long) at build time.
>
> For the time being this covers only mcount.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> tools/objtool/check.c | 16 +++++++++-------
> tools/objtool/elf.c | 8 ++++++--
> tools/objtool/include/objtool/elf.h | 8 ++++++++
> 3 files changed, 23 insertions(+), 9 deletions(-)
>
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index cef1dd54d505..fabc0ea88747 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -802,9 +802,9 @@ static int create_ibt_endbr_seal_sections(struct objtool_file *file)
> static int create_mcount_loc_sections(struct objtool_file *file)
> {
> struct section *sec;
> - unsigned long *loc;
> struct instruction *insn;
> int idx;
> + int size = elf_class_size(file->elf);

Should be renamed addrsize as per Naveen comment.

>
> sec = find_section_by_name(file->elf, "__mcount_loc");
> if (sec) {
> @@ -820,23 +820,25 @@ static int create_mcount_loc_sections(struct objtool_file *file)
> list_for_each_entry(insn, &file->mcount_loc_list, call_node)
> idx++;
>
> - sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
> + sec = elf_create_section(file->elf, "__mcount_loc", 0, size, idx);
> if (!sec)
> return -1;
>
> + sec->sh.sh_addralign = size;
> +
> idx = 0;
> list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
> + void *loc;
>
> - loc = (unsigned long *)sec->data->d_buf + idx;
> - memset(loc, 0, sizeof(unsigned long));
> + loc = sec->data->d_buf + idx;
> + memset(loc, 0, size);
>
> - if (elf_add_reloc_to_insn(file->elf, sec,
> - idx * sizeof(unsigned long),
> + if (elf_add_reloc_to_insn(file->elf, sec, idx,
> R_X86_64_64,
> insn->sec, insn->offset))
> return -1;
>
> - idx++;
> + idx += size;
> }
>
> return 0;
> diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
> index c25e957c1e52..63218f5799c2 100644
> --- a/tools/objtool/elf.c
> +++ b/tools/objtool/elf.c
> @@ -1124,6 +1124,7 @@ static struct section *elf_create_rela_reloc_section(struct elf *elf, struct sec
> {
> char *relocname;
> struct section *sec;
> + int size = elf_class_size(elf);

Should be renamed addrsize as per Naveen comment.

>
> relocname = malloc(strlen(base->name) + strlen(".rela") + 1);
> if (!relocname) {
> @@ -1133,7 +1134,10 @@ static struct section *elf_create_rela_reloc_section(struct elf *elf, struct sec
> strcpy(relocname, ".rela");
> strcat(relocname, base->name);
>
> - sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rela), 0);
> + if (size == sizeof(u32))
> + sec = elf_create_section(elf, relocname, 0, sizeof(Elf32_Rela), 0);
> + else
> + sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rela), 0);
> free(relocname);
> if (!sec)
> return NULL;
> @@ -1142,7 +1146,7 @@ static struct section *elf_create_rela_reloc_section(struct elf *elf, struct sec
> sec->base = base;
>
> sec->sh.sh_type = SHT_RELA;
> - sec->sh.sh_addralign = 8;
> + sec->sh.sh_addralign = size;
> sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
> sec->sh.sh_info = base->idx;
> sec->sh.sh_flags = SHF_INFO_LINK;
> diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
> index adebfbc2b518..c720c4476828 100644
> --- a/tools/objtool/include/objtool/elf.h
> +++ b/tools/objtool/include/objtool/elf.h
> @@ -141,6 +141,14 @@ static inline bool has_multiple_files(struct elf *elf)
> return elf->num_files > 1;
> }
>
> +static inline int elf_class_size(struct elf *elf)

Should be renamed elf_class_addrsize() as per Naveen comment.

> +{
> + if (elf->ehdr.e_ident[EI_CLASS] == ELFCLASS32)
> + return sizeof(u32);
> + else
> + return sizeof(u64);
> +}
> +
> struct elf *elf_open_read(const char *name, int flags);
> struct section *elf_create_section(struct elf *elf, const char *name, unsigned int sh_flags, size_t entsize, int nr);
>
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