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commit 5e681c46b3893d87e3156a0a6c2783de5fa41c94
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Author: Mark Wielaard <mjw@redhat.com>
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Date: Wed Aug 12 00:11:26 2015 +0200
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elflint: Add gnuld check when a NOBITS section falls inside a segment.
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gnuld has a really bad bug where it can place a NOBITS section inside
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a PT_LOAD segment. Normally that would not work. But it also makes sure
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that the contents of the file is all zeros. So in practice it is actually
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a PROGBITS section with all zero data. Except that other tools will think
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there is an unused gap in the ELF file after the NOBITS section.
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Recognize and check this pattern in elflint when --gnu is given.
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Signed-off-by: Mark Wielaard <mjw@redhat.com>
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diff --git a/src/elflint.c b/src/elflint.c
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index a916886..0d5f34d 100644
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--- a/src/elflint.c
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+++ b/src/elflint.c
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@@ -3978,9 +3978,39 @@ section [%2zu] '%s' not fully contained in segment of program header entry %d\n"
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{
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if (shdr->sh_offset < phdr->p_offset + phdr->p_filesz
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&& !is_debuginfo)
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- ERROR (gettext ("\
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+ {
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+ if (!gnuld)
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+ ERROR (gettext ("\
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section [%2zu] '%s' has type NOBITS but is read from the file in segment of program header entry %d\n"),
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- cnt, section_name (ebl, cnt), pcnt);
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+ cnt, section_name (ebl, cnt), pcnt);
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+ else
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+ {
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+ /* This is truly horrible. GNU ld might put a
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+ NOBITS section in the middle of a PT_LOAD
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+ segment, assuming the next gap in the file
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+ actually consists of zero bits...
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+ So it really is like a PROGBITS section
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+ where the data is all zeros. Check those
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+ zero bytes are really there. */
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+ bool bad;
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+ Elf_Data *databits;
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+ databits = elf_getdata_rawchunk (ebl->elf,
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+ shdr->sh_offset,
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+ shdr->sh_size,
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+ ELF_T_BYTE);
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+ bad = (databits == NULL
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+ || databits->d_size != shdr->sh_size);
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+ for (size_t idx = 0;
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+ idx < databits->d_size && ! bad;
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+ idx++)
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+ bad = ((char *) databits->d_buf)[idx] != 0;
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+
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+ if (bad)
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+ ERROR (gettext ("\
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+section [%2zu] '%s' has type NOBITS but is read from the file in segment of program header entry %d and file contents is non-zero\n"),
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+ cnt, section_name (ebl, cnt), pcnt);
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+ }
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+ }
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}
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else
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{
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