linux-kernel - [PATCH 1/2] powerpc/signal: Fix handling of SA

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Date:   Fri, 25 Jun 2021 10:49:51 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 1/2] powerpc/signal: Fix handling of SA_RESTORER sigaction
 flag

powerpc advertises support of SA_RESTORER sigaction flag.

Make it the truth.

Cc: stable@...r.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/kernel/signal_32.c | 8 ++++++--
 arch/powerpc/kernel/signal_64.c | 4 +++-
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 0608581967f0..cf3da1386595 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -769,7 +769,9 @@ int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset,
 	}
 
 	/* Save user registers on the stack */
-	if (tsk->mm->context.vdso) {
+	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
+		tramp = (unsigned long)ksig->ka.sa.sa_restorer;
+	} else if (tsk->mm->context.vdso) {
 		tramp = VDSO32_SYMBOL(tsk->mm->context.vdso, sigtramp_rt32);
 	} else {
 		tramp = (unsigned long)mctx->mc_pad;
@@ -865,7 +867,9 @@ int handle_signal32(struct ksignal *ksig, sigset_t *oldset,
 	else
 		unsafe_save_user_regs(regs, mctx, tm_mctx, 1, failed);
 
-	if (tsk->mm->context.vdso) {
+	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
+		tramp = (unsigned long)ksig->ka.sa.sa_restorer;
+	} else if (tsk->mm->context.vdso) {
 		tramp = VDSO32_SYMBOL(tsk->mm->context.vdso, sigtramp32);
 	} else {
 		tramp = (unsigned long)mctx->mc_pad;
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 1831bba0582e..fb31a334aca6 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -910,7 +910,9 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 	tsk->thread.fp_state.fpscr = 0;
 
 	/* Set up to return from userspace. */
-	if (tsk->mm->context.vdso) {
+	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
+		regs_set_return_ip(regs, (unsigned long)ksig->ka.sa.sa_restorer);
+	} else if (tsk->mm->context.vdso) {
 		regs_set_return_ip(regs, VDSO64_SYMBOL(tsk->mm->context.vdso, sigtramp_rt64));
 	} else {
 		err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
-- 
2.25.0