On Mon, Nov 12, 2012 at 06:07:43PM -0800, Eric W. Biederman wrote:
> Vivek Goyal <vgoyal at redhat.com> writes:
>
> > A 32bit arch can prepare ELF64 headers. For example for PAE case to
> > preresent file offsets 64bit but data size at the offset still remains
> > 32bit. If we just base our decision based on EI_CLASS, then we will try
> > to read 64bit data from file and can run into various issues.
> >
> > We ran into following issue when we tried to run vmcore-dmesg on a 32bit
> > PAE system vmcore which had 64bit elf headers.
> >
> > No program header covering vaddr 0xc0a6a688c0b89100found kexec bug?
> >
> > Basically we try to read value of log_buf variable from address
> > log_buf_vaddr. We read in 64bit value and then pass that value again
> > to vaddr_to_offset() in an attempt to get to actual log_buf start
> > and get error message.
> >
> > So determine the data size based on arch and read the bytes from
> > file accordingly.
>
> The basic code change is sound. However the naming is problematic.
>
> Let me suggest:
>
> static unsigned machine_pointer_bits(void)
> {
> uint8_t bits = 0;
>
> /* Default to the size of the elf class */
> switch(ehdr.e_ident[EI_CLASS]) {
> case ELFCLASS32: bits = 32; break;
> case ELFCLASS64: bits = 64; break;
> }
>
> /* Report the architectures pointer size */
> switch(ehdr.e_machine) {
> case EM_386: bits = 32; break;
> }
>
> return bits;
> }
Thanks Eric. Version 2 is on the way.
Vivek
