tree 7bf80e5edc9b5c3aedd8d8bffbf75583aba5b625
parent 5e6cbd2a05f525a5803bfbb163288b564163dc37
author Vineet Gupta <vgupta@synopsys.com> 1623206365 -0700
committer Sasha Levin <sashal@kernel.org> 1625057334 -0400

ARCv2: save ABI registers across signal handling

commit 96f1b00138cb8f04c742c82d0a7c460b2202e887 upstream.

ARCv2 has some configuration dependent registers (r30, r58, r59) which
could be targetted by the compiler. To keep the ABI stable, these were
unconditionally part of the glibc ABI
(sysdeps/unix/sysv/linux/arc/sys/ucontext.h:mcontext_t) however we
missed populating them (by saving/restoring them across signal
handling).

This patch fixes the issue by
 - adding arcv2 ABI regs to kernel struct sigcontext
 - populating them during signal handling

Change to struct sigcontext might seem like a glibc ABI change (although
it primarily uses ucontext_t:mcontext_t) but the fact is
 - it has only been extended (existing fields are not touched)
 - the old sigcontext was ABI incomplete to begin with anyways

Fixes: https://github.com/foss-for-synopsys-dwc-arc-processors/linux/issues/53
Cc: <stable@vger.kernel.org>
Tested-by: kernel test robot <lkp@intel.com>
Reported-by: Vladimir Isaev <isaev@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>