69 lines
2.6 KiB
Diff
69 lines
2.6 KiB
Diff
commit 55c5c9a568ed707bcea1388bf3a525212d8cf4b8
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Author: Mark Wielaard <mark@klomp.org>
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Date: Wed Aug 19 23:41:24 2020 +0200
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libelf: Fixup SHF_COMPRESSED sh_addralign in elf_update if necessary.
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In elf_getdata.c we have the following to compensate for possibly
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bad sh_addralign values of compressed sections:
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/* Compressed data has a header, but then compressed data.
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Make sure to set the alignment of the header explicitly,
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don't trust the file alignment for the section, it is
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often wrong. */
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if ((flags & SHF_COMPRESSED) != 0)
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{
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entsize = 1;
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align = __libelf_type_align (elf->class, ELF_T_CHDR);
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}
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Which makes sure the d_data alignment is correct for the Chdr struct
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at the start of the compressed section.
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But this means that if a user just reads such a compressed section
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without changing it, and then tries to write it out again using
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elf_update they get an error message about d_align and sh_addralign
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being out of sync.
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We already correct obviously incorrect sh_entsize fields.
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Do the same for the sh_addralign field of a SHF_COMPRESSED section.
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Signed-off-by: Mark Wielaard <mark@klomp.org>
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diff --git a/libelf/ChangeLog b/libelf/ChangeLog
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index 8f6d2d2d..77044c1c 100644
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--- a/libelf/ChangeLog
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+++ b/libelf/ChangeLog
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@@ -1,3 +1,8 @@
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+2020-08-19 Mark Wielaard <mark@klomp.org>
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+
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+ * elf32_updatenull.c (updatenull_wrlock): Fixup the sh_addralign
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+ of an SHF_COMPRESSED section if necessary.
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+
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2020-06-04 Mark Wielaard <mark@klomp.org>
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* elf.h: Update from glibc.
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diff --git a/libelf/elf32_updatenull.c b/libelf/elf32_updatenull.c
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index 5f3cdbf6..d0d4d1eb 100644
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--- a/libelf/elf32_updatenull.c
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+++ b/libelf/elf32_updatenull.c
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@@ -267,6 +267,18 @@ __elfw2(LIBELFBITS,updatenull_wrlock) (Elf *elf, int *change_bop, size_t shnum)
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update_if_changed (shdr->sh_entsize, sh_entsize,
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scn->shdr_flags);
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+ /* Likewise for the alignment of a compressed section.
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+ For a SHF_COMPRESSED section set the correct
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+ sh_addralign value, which must match the d_align of
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+ the data (see __libelf_set_rawdata in elf_getdata.c). */
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+ if ((shdr->sh_flags & SHF_COMPRESSED) != 0)
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+ {
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+ sh_align = __libelf_type_align (ELFW(ELFCLASS,LIBELFBITS),
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+ ELF_T_CHDR);
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+ update_if_changed (shdr->sh_addralign, sh_align,
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+ scn->shdr_flags);
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+ }
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+
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if (scn->data_read == 0
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&& __libelf_set_rawdata_wrlock (scn) != 0)
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/* Something went wrong. The error value is already set. */
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