On 27/11/2024 01:50, Eduard Zingerman wrote:
btf_encoder__tag_kfuncs() reads .BTF_ids section to identify a set of kfuncs present in the ELF file being processed. This section consists of: - arrays of uint32_t elements; - arrays of records with the following structure: struct btf_id_and_flag { uint32_t id; uint32_t flags; }; When endianness of a binary operated by pahole differs from the host system's endianness, these fields require byte-swapping before use. Currently, this byte-swapping does not occur, resulting in kfuncs not being marked with declaration tags. This commit resolves the issue by using elf_getdata_rawchunk() function to read .BTF_ids section data. When called with ELF_T_WORD as 'type' parameter it does necessary byte order conversion (only if host and elf endianness do not match). Cc: Alan Maguire <alan.maguire@xxxxxxxxxx> Cc: Andrii Nakryiko <andrii@xxxxxxxxxx> Cc: Daniel Xu <dxu@xxxxxxxxx> Cc: Jiri Olsa <olsajiri@xxxxxxxxx> Cc: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> Cc: Vadim Fedorenko <vadfed@xxxxxxxx> Fixes: 72e88f29c6f7 ("pahole: Inject kfunc decl tags into BTF") Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx> --- btf_encoder.c | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) diff --git a/btf_encoder.c b/btf_encoder.c index e1adddf..3754884 100644 --- a/btf_encoder.c +++ b/btf_encoder.c @@ -1904,18 +1904,32 @@ static int btf_encoder__tag_kfuncs(struct btf_encoder *encoder) goto out; }- data = elf_getdata(scn, 0);- if (!data) { - elf_error("Failed to get ELF section(%d) data", i); - goto out; - } - if (shdr.sh_type == SHT_SYMTAB) { + data = elf_getdata(scn, 0); + if (!data) { + elf_error("Failed to get ELF section(%d) data", i); + goto out; + } + symbols_shndx = i; symscn = scn; symbols = data; strtabidx = shdr.sh_link; } else if (!strcmp(secname, BTF_IDS_SECTION)) { + /* .BTF_ids section consists of uint32_t elements, + * and thus might need byte order conversion. + * However, it has type PROGBITS, hence elf_getdata() + * won't automatically do the conversion. + * Use elf_getdata_rawchunk() instead, + * ELF_T_WORD tells it to do the necessary conversion. + */ + data = elf_getdata_rawchunk(elf, shdr.sh_offset, shdr.sh_size, ELF_T_WORD); + if (!data) { + elf_error("Failed to get %s ELF section(%d) data", + BTF_IDS_SECTION, i); + goto out; + } + idlist_shndx = i; idlist_addr = shdr.sh_addr; idlist = data;
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@xxxxxxxxx>
