On Mon, May 10, 2010 at 03:09:20PM +0300, Mika Westerberg wrote: > I believe that when passing ELF64 header, it fails in following checks: > > /* Make sure it's an ARM executable */ > if (x->e_ident[EI_CLASS] != ELF_CLASS) > return 0; > if (x->e_machine != EM_ARM) > return 0; > > ELF_CLASS is defined in arch/arm/include/asm/elf.h: > > #define ELF_CLASS ELFCLASS32 > > So if class is different than ELFCLASS32 it returns 0 and never even try to > access other fields, right? Yes. > > Now, here's the question: why does this crashkernel stuff want to > > parse a 64-bit ELF header on a 32-bit only platform where the crashing > > kernel will never generate a 64-bit ELF core file? > > I really don't know but fs/proc/vmcore.c is coded in such way that it supports > both types of ELF headers. It however, passes the header to elf_check_arch() > which in our case should fail if it is something else than ELF32 header. There's other arches which want elf_check_arch to be a function call, so I think my question needs to be looked at more closely - and possibly the code changed such that we don't end up with this situation. Maybe a cleaner solution would be for vmcore.c to split its calls to elf_check_arch() - to be elf32_check_arch() and elf64_check_arch() ? Platforms where it's just a macro can define both to be elf_check_arch() but those where only one flavour is supported should define the unsupported flavour to zero - which incidentally would allow the compiler to optimize away the unnecessary parts of parse_crash_elf*_headers().
