xtensa: fix fast_syscall_spill_registers
authorChris Zankel <chris@zankel.net>
Wed, 29 Jan 2014 06:09:51 +0000 (22:09 -0800)
committerChris Zankel <chris@zankel.net>
Wed, 29 Jan 2014 06:09:51 +0000 (22:09 -0800)
commit6b5a1f74e50170e64104135490dc32b657483594
tree6bb08372aa016f77f27ec12d8ce4bbcc16291af0
parent3251f1e27a5a17f0efd436cfd1e7b9896cfab0a0
xtensa: fix fast_syscall_spill_registers

The original implementation could clobber registers under certain conditions.

The Xtensa processor architecture uses windowed registers and the original
implementation was using a4 as a temporary register, which under certain
conditions could be register a0 of the oldest window frame, and didn't always
restore the content correctly.

By moving the _spill_registers routine inside the fast system call, it frees
up one more register (the return address is not required anymore) for the
spill routine.

Signed-off-by: Chris Zankel <chris@zankel.net>
arch/xtensa/kernel/entry.S