[PATCH v2 08/13] arm64/fpsimd: Reset FPMR upon exec()

[Mark Rutland]

An exec() is expected to reset all FPSIMD/SVE/SME state, and barring
special handling of the vector lengths, the state is expected to reset
to zero. This reset is handled in fpsimd_flush_thread(), which the core
exec() code calls via flush_thread().

When support was added for FPMR, no logic was added to
fpsimd_flush_thread() to reset the FPMR value, and thus it is
erroneously inherited across an exec().

Add the missing reset of FPMR.

Fixes: 203f2b95a882dc46 ("arm64/fpsimd: Support FEAT_FPMR")
Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Mark Brown <broonie at kernel.org>
Cc: Will Deacon <will at kernel.org>
Reviewed-by: Mark Brown <broonie at kernel.org>
---
 arch/arm64/kernel/fpsimd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 4a0b0bb3a3fad..0b6fda5b7bad5 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1638,6 +1638,9 @@ void fpsimd_flush_thread(void)
 		current->thread.svcr = 0;
 	}
 
+	if (system_supports_fpmr())
+		current->thread.uw.fpmr = 0;
+
 	current->thread.fp_type = FP_STATE_FPSIMD;
 
 	put_cpu_fpsimd_context();
-- 
2.30.2