Hi,
On 08/21/2018 05:31 PM, Nick Clifton wrote:
if (filedata->section_headers != NULL
&& header->e_shstrndx == (SHN_XINDEX & 0xffff))
printf (" (%u)", filedata->section_headers[0].sh_link);
else if (header->e_shstrndx != SHN_UNDEF
&& header->e_shstrndx >= header->e_shnum)
printf (_(" <corrupt: out of range>"));
[...]
Note - the use if "& 0xffff" in the above code is confusing, and looks
surplus to me, but I do not think that it makes any difference to the
behaviour.
I haven't checked the location of this quoted code; however, the use of
"& 0xffff" is probably due to a clever hack made internally:
Elf[32|64]_External_Ehdr in include/elf/external.h declares e_shstrndx
as 2 bytes,
while Elf_Internal_Ehdr in include/elf/internal.h declares it as 4
bytes because we would like to be able to keep the overflowing values
within the same variable without extra checks.
We would like to be able to store values that are reserved or higher
than 0xffff as valid indices internally in the 4-byte e_shstrndx.
Therefore, some constants including SHN_XINDEX are re-defined in
elf/internal.h as 4 byte values. These redefinitions hold the new bounds
on such indices. Because of this internal simplification, though, we
need to use "& 0xffff" to get the 2-byte value that's used when reading
values in or outputting them.
Regards,
Egeyar
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