When FPMR and SME are both present then entering and exiting streaming mode clears FPMR in the same manner as it clears the V/Z and P registers. Since entering and exiting streaming mode via ptrace is expected to have the same effect as doing so via SMSTART/SMSTOP it should clear FPMR too but this was missed when FPMR support was added. Add the required reset of FPMR.
Since changing the vector length resets SVCR a SME vector length change implemented via a write to ZA can trigger an exit of streaming mode and we need to check when writing to ZA as well.
Fixes: 4035c22ef7d4 ("arm64/ptrace: Expose FPMR via ptrace") Signed-off-by: Mark Brown broonie@kernel.org Cc: stable@vger.kernel.org --- arch/arm64/kernel/ptrace.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index b756578aeaeea1d3250276734520e3eaae8a671d..f242df53de2992bf8a3fd51710d6653fe82f7779 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -876,6 +876,7 @@ static int sve_set_common(struct task_struct *target, const void *kbuf, const void __user *ubuf, enum vec_type type) { + u64 old_svcr = target->thread.svcr; int ret; struct user_sve_header header; unsigned int vq; @@ -903,8 +904,6 @@ static int sve_set_common(struct task_struct *target,
/* Enter/exit streaming mode */ if (system_supports_sme()) { - u64 old_svcr = target->thread.svcr; - switch (type) { case ARM64_VEC_SVE: target->thread.svcr &= ~SVCR_SM_MASK; @@ -1003,6 +1002,10 @@ static int sve_set_common(struct task_struct *target, start, end);
out: + /* If we entered or exited streaming mode then reset FPMR */ + if ((target->thread.svcr & SVCR_SM) != (old_svcr & SVCR_SM)) + target->thread.uw.fpmr = 0; + fpsimd_flush_task_state(target); return ret; } @@ -1099,6 +1102,7 @@ static int za_set(struct task_struct *target, unsigned int pos, unsigned int count, const void *kbuf, const void __user *ubuf) { + u64 old_svcr = target->thread.svcr; int ret; struct user_za_header header; unsigned int vq; @@ -1175,6 +1179,10 @@ static int za_set(struct task_struct *target, target->thread.svcr |= SVCR_ZA_MASK;
out: + /* If we entered or exited streaming mode then reset FPMR */ + if ((target->thread.svcr & SVCR_SM) != (old_svcr & SVCR_SM)) + target->thread.uw.fpmr = 0; + fpsimd_flush_task_state(target); return ret; }
--- base-commit: 8e929cb546ee42c9a61d24fae60605e9e3192354 change-id: 20241106-arm64-ptrace-fpmr-sm-45390f592574
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