On Wed, 2018-06-20 at 00:57 +0200, Mark Wielaard wrote: > 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.
Pushed to master.
