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author | Jiri Olsa <jolsa@kernel.org> | 2020-08-19 11:23:42 +0200 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2020-08-20 14:17:20 -0700 |
commit | 51f6463aacfbfd322bcaadc606da56acef644b05 (patch) | |
tree | b0c83afdb2a5096ffa62c9e66a5e04dcc0ca2d73 /tools | |
parent | 1e891e513e16c145cc9b45b1fdb8bf4a4f2f9557 (diff) | |
download | linux-51f6463aacfbfd322bcaadc606da56acef644b05.tar.gz linux-51f6463aacfbfd322bcaadc606da56acef644b05.tar.bz2 linux-51f6463aacfbfd322bcaadc606da56acef644b05.zip |
tools/resolve_btfids: Fix sections with wrong alignment
The data of compressed section should be aligned to 4
(for 32bit) or 8 (for 64 bit) bytes.
The binutils ld sets sh_addralign to 1, which makes libelf
fail with misaligned section error during the update as
reported by Jesper:
FAILED elf_update(WRITE): invalid section alignment
While waiting for ld fix, we can fix compressed sections
sh_addralign value manually.
Adding warning in -vv mode when the fix is triggered:
$ ./tools/bpf/resolve_btfids/resolve_btfids -vv vmlinux
...
section(36) .comment, size 44, link 0, flags 30, type=1
section(37) .debug_aranges, size 45684, link 0, flags 800, type=1
- fixing wrong alignment sh_addralign 16, expected 8
section(38) .debug_info, size 129104957, link 0, flags 800, type=1
- fixing wrong alignment sh_addralign 1, expected 8
section(39) .debug_abbrev, size 1152583, link 0, flags 800, type=1
- fixing wrong alignment sh_addralign 1, expected 8
section(40) .debug_line, size 7374522, link 0, flags 800, type=1
- fixing wrong alignment sh_addralign 1, expected 8
section(41) .debug_frame, size 702463, link 0, flags 800, type=1
section(42) .debug_str, size 1017571, link 0, flags 830, type=1
- fixing wrong alignment sh_addralign 1, expected 8
section(43) .debug_loc, size 3019453, link 0, flags 800, type=1
- fixing wrong alignment sh_addralign 1, expected 8
section(44) .debug_ranges, size 1744583, link 0, flags 800, type=1
- fixing wrong alignment sh_addralign 16, expected 8
section(45) .symtab, size 2955888, link 46, flags 0, type=2
section(46) .strtab, size 2613072, link 0, flags 0, type=3
...
update ok for vmlinux
Another workaround is to disable compressed debug info data
CONFIG_DEBUG_INFO_COMPRESSED kernel option.
Fixes: fbbb68de80a4 ("bpf: Add resolve_btfids tool to resolve BTF IDs in ELF object")
Reported-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Yonghong Song <yhs@fb.com>
Cc: Mark Wielaard <mjw@redhat.com>
Cc: Nick Clifton <nickc@redhat.com>
Link: https://lore.kernel.org/bpf/20200819092342.259004-1-jolsa@kernel.org
Diffstat (limited to 'tools')
-rw-r--r-- | tools/bpf/resolve_btfids/main.c | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c index 4d9ecb975862..0def0bb1f783 100644 --- a/tools/bpf/resolve_btfids/main.c +++ b/tools/bpf/resolve_btfids/main.c @@ -233,6 +233,39 @@ static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size) return btf_id__add(root, id, false); } +/* + * The data of compressed section should be aligned to 4 + * (for 32bit) or 8 (for 64 bit) bytes. The binutils ld + * sets sh_addralign to 1, which makes libelf fail with + * misaligned section error during the update: + * FAILED elf_update(WRITE): invalid section alignment + * + * While waiting for ld fix, we fix the compressed sections + * sh_addralign value manualy. + */ +static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh) +{ + int expected = gelf_getclass(elf) == ELFCLASS32 ? 4 : 8; + + if (!(sh->sh_flags & SHF_COMPRESSED)) + return 0; + + if (sh->sh_addralign == expected) + return 0; + + pr_debug2(" - fixing wrong alignment sh_addralign %u, expected %u\n", + sh->sh_addralign, expected); + + sh->sh_addralign = expected; + + if (gelf_update_shdr(scn, sh) == 0) { + printf("FAILED cannot update section header: %s\n", + elf_errmsg(-1)); + return -1; + } + return 0; +} + static int elf_collect(struct object *obj) { Elf_Scn *scn = NULL; @@ -309,6 +342,9 @@ static int elf_collect(struct object *obj) obj->efile.idlist_shndx = idx; obj->efile.idlist_addr = sh.sh_addr; } + + if (compressed_section_fix(elf, scn, &sh)) + return -1; } return 0; |