linux-kernel - [PATCH] arm64/signal: Don't assume that TIF

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Message-Id: <20240119-arm64-sve-signal-regs-v1-1-b9fd61b0289a@kernel.org>
Date: Fri, 19 Jan 2024 12:29:13 +0000
From: Mark Brown <broonie@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>, 
 Will Deacon <will@...nel.org>
Cc: Dave Martin <dave.martin@....com>, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>, 
 stable@...r.kernel.org
Subject: [PATCH] arm64/signal: Don't assume that TIF_SVE means we saved SVE
 state

When we are in a syscall we will only save the FPSIMD subset even though
the task still has access to the full register set, and on context switch
we will only remove TIF_SVE when loading the register state. This means
that the signal handling code should not assume that TIF_SVE means that
the register state is stored in SVE format, it should instead check the
format that was recorded during save.

Fixes: 8c845e273104 ("arm64/sve: Leave SVE enabled on syscall if we don't context switch")
Signed-off-by: Mark Brown <broonie@...nel.org>
Cc:  <stable@...r.kernel.org>
---
 arch/arm64/kernel/fpsimd.c | 2 +-
 arch/arm64/kernel/signal.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 1559c706d32d..80133c190136 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1626,7 +1626,7 @@ void fpsimd_preserve_current_state(void)
 void fpsimd_signal_preserve_current_state(void)
 {
 	fpsimd_preserve_current_state();
-	if (test_thread_flag(TIF_SVE))
+	if (current->thread.fp_type == FP_STATE_SVE)
 		sve_to_fpsimd(current);
 }
 
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 0e8beb3349ea..425b1bc17a3f 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -242,7 +242,7 @@ static int preserve_sve_context(struct sve_context __user *ctx)
 		vl = task_get_sme_vl(current);
 		vq = sve_vq_from_vl(vl);
 		flags |= SVE_SIG_FLAG_SM;
-	} else if (test_thread_flag(TIF_SVE)) {
+	} else if (current->thread.fp_type == FP_STATE_SVE) {
 		vq = sve_vq_from_vl(vl);
 	}
 
@@ -878,7 +878,7 @@ static int setup_sigframe_layout(struct rt_sigframe_user_layout *user,
 	if (system_supports_sve() || system_supports_sme()) {
 		unsigned int vq = 0;
 
-		if (add_all || test_thread_flag(TIF_SVE) ||
+		if (add_all || current->thread.fp_type == FP_STATE_SVE ||
 		    thread_sm_enabled(&current->thread)) {
 			int vl = max(sve_max_vl(), sme_max_vl());
 

---
base-commit: 0dd3ee31125508cd67f7e7172247f05b7fd1753a
change-id: 20240118-arm64-sve-signal-regs-5711e0d10425

Best regards,
-- 
Mark Brown <broonie@...nel.org>