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| author | Mark Wielaard <mark@klomp.org> | 2018-06-12 12:54:35 +0200 |
|---|---|---|
| committer | Mark Wielaard <mark@klomp.org> | 2018-06-22 17:52:34 +0200 |
| commit | dd813335c352adb53972bdc63495650dba0c987f (patch) | |
| tree | dec852640f6c473f89895a33dca5e7afa283b02e /libelf/libelfP.h | |
| parent | c1990d36cfe37a30bcc49422c37a6767fd190559 (diff) | |
| download | elfutils-dd813335c352adb53972bdc63495650dba0c987f.tar.gz | |
libelf: Don't return unaligned data returned from elf_getdata[_rawchunk].
For i386 and x86_64 we allow some unaligned data accesses.
We also return unaligned data from elf_getdata[_rawchunk].
But that might go wrong if we then access the ELF types inside.
When build with gcc -O3 for example the compiler might vectorize
loops accessing ELF words or types. The instructions used do require
the data is naturally aligned. If the function returnes unaligned
data the program will segfault and crash. This happens for example
with the code in dwfl_module_getdwarf.c that tries to iterate over
the hash buckets gotten through elf_getdata_rawchunk based on the
DT_[GNU]_HASH value.
This only happens when the underlying ELF file is mmapped, and it
is meant as optimization so that we don't have to copy data first
so that it is correctly aligned. In most cases the data is already
naturally aligned though. But it might not be for non-native ELF
files.
Given that it might even happen in our own code base and these
are public functions that can be used by code that might rely on
the data returned being correctly aligned for the ELF data type
requested just always return correctly aligned data.
Signed-off-by: Mark Wielaard <mark@klomp.org>
Diffstat (limited to 'libelf/libelfP.h')
| -rw-r--r-- | libelf/libelfP.h | 4 |
1 files changed, 0 insertions, 4 deletions
diff --git a/libelf/libelfP.h b/libelf/libelfP.h index ca805ac4..ed216c8c 100644 --- a/libelf/libelfP.h +++ b/libelf/libelfP.h @@ -443,15 +443,11 @@ extern int __libelf_version_initialized attribute_hidden; # define LIBELF_EV_IDX (__libelf_version - 1) #endif -#if !ALLOW_UNALIGNED /* Array with alignment requirements of the internal types indexed by ELF version, binary class, and type. */ extern const uint_fast8_t __libelf_type_aligns[EV_NUM - 1][ELFCLASSNUM - 1][ELF_T_NUM] attribute_hidden; # define __libelf_type_align(class, type) \ (__libelf_type_aligns[LIBELF_EV_IDX][class - 1][type] ?: 1) -#else -# define __libelf_type_align(class, type) 1 -#endif /* Given an Elf handle and a section type returns the Elf_Data d_type. Should not be called when SHF_COMPRESSED is set, the d_type should |