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| author | Alan Modra <amodra@gmail.com> | 2022-02-15 20:11:03 +1030 |
|---|---|---|
| committer | Alan Modra <amodra@gmail.com> | 2022-02-16 22:05:10 +1030 |
| commit | 1f9b1a84350d3755ce8620900a35c3d1997535e6 (patch) | |
| tree | faf43bbd8090ba94d17758ac78e56dee925253a5 /bfd/elf.c | |
| parent | 6e731729881ae4c1a9542843c29a3981166c9e45 (diff) | |
| download | gdb-1f9b1a84350d3755ce8620900a35c3d1997535e6.zip gdb-1f9b1a84350d3755ce8620900a35c3d1997535e6.tar.gz gdb-1f9b1a84350d3755ce8620900a35c3d1997535e6.tar.bz2 | |
What to do when sh_addralign isn't a power of two
BFD generally doesn't handle anything but a power of two section
alignment, and ELF sh_addralign is required to be an integral power of
two (or zero) by the ELF spec. Of course this is ignored by fuzzers,
and because bfd_log2 rounds up, we can end up with alignment_power
being 32 on a 32-bit object or 64 on a 64-bit object. That then
triggers ubsan warnings in places like bfd_update_compression_header
where we want to convert from alignment_power back to an alignment.
I suppose we could reject object files that have non-compliant
sh_addralign, but I think it's also reasonable to use the greatest
power of two divisor of sh_addralign, ie. the rightmost 1 bit.
* elf.c (_bfd_elf_make_section_from_shdr): Use greatest power
of two divisor of sh_addralign.
(_bfd_elf_assign_file_position_for_section): Likewise.
(assign_file_positions_for_non_load_sections): Likewise.
Diffstat (limited to 'bfd/elf.c')
| -rw-r--r-- | bfd/elf.c | 13 |
1 files changed, 7 insertions, 6 deletions
@@ -1104,7 +1104,8 @@ _bfd_elf_make_section_from_shdr (bfd *abfd, if (!bfd_set_section_vma (newsect, hdr->sh_addr / opb) || !bfd_set_section_size (newsect, hdr->sh_size) - || !bfd_set_section_alignment (newsect, bfd_log2 (hdr->sh_addralign))) + || !bfd_set_section_alignment (newsect, bfd_log2 (hdr->sh_addralign + & -hdr->sh_addralign))) return false; /* As a GNU extension, if the name begins with .gnu.linkonce, we @@ -4227,7 +4228,7 @@ _bfd_elf_assign_file_position_for_section (Elf_Internal_Shdr *i_shdrp, bool align) { if (align && i_shdrp->sh_addralign > 1) - offset = BFD_ALIGN (offset, i_shdrp->sh_addralign); + offset = BFD_ALIGN (offset, i_shdrp->sh_addralign & -i_shdrp->sh_addralign); i_shdrp->sh_offset = offset; if (i_shdrp->bfd_section != NULL) i_shdrp->bfd_section->filepos = offset; @@ -6149,6 +6150,7 @@ assign_file_positions_for_non_load_sections (bfd *abfd, for (hdrpp = i_shdrpp + 1; hdrpp < end_hdrpp; hdrpp++) { Elf_Internal_Shdr *hdr; + bfd_vma align; hdr = *hdrpp; if (hdr->bfd_section != NULL @@ -6174,11 +6176,10 @@ assign_file_positions_for_non_load_sections (bfd *abfd, : hdr->bfd_section->name)); /* We don't need to page align empty sections. */ if ((abfd->flags & D_PAGED) != 0 && hdr->sh_size != 0) - off += vma_page_aligned_bias (hdr->sh_addr, off, - maxpagesize); + align = maxpagesize; else - off += vma_page_aligned_bias (hdr->sh_addr, off, - hdr->sh_addralign); + align = hdr->sh_addralign & -hdr->sh_addralign; + off += vma_page_aligned_bias (hdr->sh_addr, off, align); off = _bfd_elf_assign_file_position_for_section (hdr, off, false); } |