Re: [PATCH v3 2/5] Change xstate_bv handling to use 8 bytes of data.

Pedro Alves
2017-01-26T14:46:12Z

On 12/06/2016 10:58 AM, Michael Sturm wrote:
> The size of the state-component bitmap as specified in
> Intel(R) 64 and IA-32 Architectures Software Developer's Manual,
> Chapter 13.4.2 is 8 bytes.
> So far, the data types used for xstate_bv_p (gdb_byte*),
> clear_bv (unsigned int) and tdep->xcr0 (uint64_t) were
> inconsistent. But, since the xstate components were still
> fitting into a single byte, the code still worked
> as expected.
> However, with the addition of the PKU feature (bit 9),
> using one byte for the bitmap will no longer be sufficient.
>
> This patch changes related code to use 64 bit data types
> consistently and changes read/write acces of the XSAVE
> header in the xsave buffer to use the endianess-aware
> functions extract_unsigned_integer and store_unsigned_integer.

The typing is a bit inconsistent, with some places using
unsigned long long, while others ULONGEST. It'd be nice to
use uint64_t if we exactly mean 64-bit.

But that's for another day. Meanwhile, this LGTM.

> * i387-tdep.c (i387_supply_xsave): Change type
> of clear_bv to ULONGEST. Replace gdb_byte *xstate_bv_p
> with ULONGEST xstate_bv and use extract_unsigned_integer
> and store_unsigned_integer to read/write its value from
> the xsave buffer. This is required to make sure that
> eventual differences in endianess between host and
> target are taken care off.

The "This is required ..." part belongs in the commit log.
The ChangeLogs only mention the "what", not the "why".

Thanks,
Pedro Alves