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SubjectRe: [PATCH] perf symbol: Look for ImageBase in PE file to compute .text offset
Em Thu, Sep 09, 2021 at 09:26:36PM +0200, Remi Bernon escreveu:
> Instead of using the file offset in the debug file.
>
> This fixes a regression from 00a3423492bc90be99e529a64f13fdd80a0e8c0a,
> causing incorrect symbol resolution when debug file have been stripped
> from non-debug sections (in which case its .text section is empty and
> doesn't have any file position).
>
> The debug files could also be created with a different file alignment,
> and have different file positions from the mmap-ed binary, or have the
> section reordered.
>
> This instead looks for the file image base, using the corresponding bfd
> *ABS* symbols. As PE symbols only have 4 bytes, it also needs to keep
> .text section vma high bits.

I added a:

Fixes: 00a3423492bc90be ("perf symbols: Make dso__load_bfd_symbols() load PE files from debug cache only")

To help stable@kernel.org to pick it, its on my local tree now.

It would be great to get a:

Reviewed-by: Nicholas Fraser <nfraser@codeweavers.com>

Can we have it, please?

- Arnaldo

> Signed-off-by: Remi Bernon <rbernon@codeweavers.com>
> ---
>
> Hi!
>
> As I'm not updating it often I only recently realized that perf had a
> regression when using stripped debug info files, and all symbols from
> PE files are off. This should make things better.
>
> Cheers,
>
> tools/perf/util/symbol.c | 20 ++++++++++++++++----
> 1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 77fc46ca07c0..0fc9a5410739 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1581,10 +1581,6 @@ int dso__load_bfd_symbols(struct dso *dso, const char *debugfile)
> if (bfd_get_flavour(abfd) == bfd_target_elf_flavour)
> goto out_close;
>
> - section = bfd_get_section_by_name(abfd, ".text");
> - if (section)
> - dso->text_offset = section->vma - section->filepos;
> -
> symbols_size = bfd_get_symtab_upper_bound(abfd);
> if (symbols_size == 0) {
> bfd_close(abfd);
> @@ -1602,6 +1598,22 @@ int dso__load_bfd_symbols(struct dso *dso, const char *debugfile)
> if (symbols_count < 0)
> goto out_free;
>
> + section = bfd_get_section_by_name(abfd, ".text");
> + if (section) {
> + for (i = 0; i < symbols_count; ++i) {
> + if (!strcmp(bfd_asymbol_name(symbols[i]), "__ImageBase") ||
> + !strcmp(bfd_asymbol_name(symbols[i]), "__image_base__"))
> + break;
> + }
> + if (i < symbols_count) {
> + /* PE symbols can only have 4 bytes, so use .text high bits */
> + dso->text_offset = section->vma - (u32)section->vma;
> + dso->text_offset += (u32)bfd_asymbol_value(symbols[i]);
> + } else {
> + dso->text_offset = section->vma - section->filepos;
> + }
> + }
> +
> qsort(symbols, symbols_count, sizeof(asymbol *), bfd_symbols__cmpvalue);
>
> #ifdef bfd_get_section
> --
> 2.33.0

--

- Arnaldo

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