Re: [Patch V2 1/2] sparc64 changes for gdb-7.6

[Dave Kleikamp <dave.kleikamp@oracle.com>]

On 03/24/2016 02:20 PM, David Miller wrote:
> From: Dave Kleikamp <dave.kleikamp@oracle.com>
> Date: Wed, 23 Mar 2016 17:41:07 -0500
> 
>> +   /* If the section has relocations, we must read it ourselves.
>> +-     Otherwise we attach it to the BFD.  */
>> ++     Otherwise we attach it to the BFD.  
>> ++     Also, in sparc64 only try mmap for sections which
>> ++     are properly aligned in order to avoid SIGBUS errors.  */
>> ++
>> ++#if defined(__sparc__) && __WORDSIZE = 64
>> ++  if (info->size > 4 * pagesize && (sectp->flags & SEC_RELOC) = 0 && !(sectp->filepos & 0x3))
>> ++#else
>> +   if ((sectp->flags & SEC_RELOC) = 0)
>> ++#endif
>> +     {
>> +       const gdb_byte *bytes = gdb_bfd_map_section (sectp, &info->size);
> 
> This doesn't make any sense at all.
> 
> The bug is probably that unaligned relocations are being improperly
> accessed using 32-bit loads and storess them.
> 
> Several relocs, particularly those used in debugging sections, need to
> be carefully accessed using byte at a time accesses in order to avoid
> said SIGBUS problem.
> 
> BFD and the rest of binutils have code to handle this case properly.
> 
> Please don't paper over the core issue with hacks like this.

I have to admit that I don't know the whole story here. I took over the
crash port, but haven't had to touch the gdb patch that got handed to
me. What I do know is crash works off an older 7.6 branch of gdb. I'll
get back to you after I talk to some other folks.

Thanks,
Dave