[PATCH v1 1/2] powerpc/64s: system call scv tabort fix for corrupt irq soft-mask state

[PATCH v1 1/2] powerpc/64s: system call scv tabort fix for corrupt irq soft-mask state

[Nicholas Piggin]

If a system call is made with a transaction active, the kernel
immediately aborts it and returns. scv system calls disable irqs even
earlier in their interrupt handler, and tabort_syscall does not fix this
up.

This can result in irq soft-mask state being messed up on the next
kernel entry, and crashing at BUG_ON(arch_irq_disabled_regs(regs)) in
the kernel exit handlers, or possibly worse.

Fix this by having tabort_syscall setting irq soft-mask back to enabled.

Reported-by: Eirik Fuller <efuller@redhat.com>
Fixes: 7fa95f9adaee7 ("powerpc/64s: system call support for scv/rfscv instructions")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/interrupt_64.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index d4212d2ff0b5..44f99df36fb2 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -438,6 +438,10 @@ _ASM_NOKPROBE_SYMBOL(tabort_syscall)
 	li	r9, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT)
 	TABORT(R9)
 
+	/* scv has disabled irqs so must re-enable. sc just remains enabled */
+	li	r9,IRQS_ENABLED
+	stb	r9,PACAIRQSOFTMASK(r13)
+
 	/*
 	 * Return directly to userspace. We have corrupted user register state,
 	 * but userspace will never see that register state. Execution will
-- 
2.23.0

[PATCH v1 2/2] selftests/powerpc: Add scv versions of the basic TM syscall tests

[Nicholas Piggin]

The basic TM vs syscall test code hard codes an sc instruction for the
system call, which fails to cover scv even when the userspace libc has
support for it.

Duplicate the tests with hard coded scv variants so both are tested
when possible.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 .../selftests/powerpc/tm/tm-syscall-asm.S     | 46 +++++++++++++++++++
 .../testing/selftests/powerpc/tm/tm-syscall.c | 36 ++++++++++++---
 2 files changed, 75 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/powerpc/tm/tm-syscall-asm.S b/tools/testing/selftests/powerpc/tm/tm-syscall-asm.S
index bd1ca25febe4..849316831e6a 100644
--- a/tools/testing/selftests/powerpc/tm/tm-syscall-asm.S
+++ b/tools/testing/selftests/powerpc/tm/tm-syscall-asm.S
@@ -2,6 +2,10 @@
 #include <ppc-asm.h>
 #include <asm/unistd.h>
 
+/* ppc-asm.h does not define r0 or r1 */
+#define r0 0
+#define r1 1
+
 	.text
 FUNC_START(getppid_tm_active)
 	tbegin.
@@ -26,3 +30,45 @@ FUNC_START(getppid_tm_suspended)
 1:
 	li	r3, -1
 	blr
+
+FUNC_START(getppid_scv_tm_active)
+	mflr	r0
+	std	r0,16(r1)
+	stdu	r1,-32(r1)
+	tbegin.
+	beq 1f
+	li	r0, __NR_getppid
+	scv	0
+	tend.
+	addi	r1,r1,32
+	ld	r0,16(r1)
+	mtlr	r0
+	blr
+1:
+	li	r3, -1
+	addi	r1,r1,32
+	ld	r0,16(r1)
+	mtlr	r0
+	blr
+
+FUNC_START(getppid_scv_tm_suspended)
+	mflr	r0
+	std	r0,16(r1)
+	stdu	r1,-32(r1)
+	tbegin.
+	beq 1f
+	li	r0, __NR_getppid
+	tsuspend.
+	scv	0
+	tresume.
+	tend.
+	addi	r1,r1,32
+	ld	r0,16(r1)
+	mtlr	r0
+	blr
+1:
+	li	r3, -1
+	addi	r1,r1,32
+	ld	r0,16(r1)
+	mtlr	r0
+	blr
diff --git a/tools/testing/selftests/powerpc/tm/tm-syscall.c b/tools/testing/selftests/powerpc/tm/tm-syscall.c
index becb8207b432..9a822208680e 100644
--- a/tools/testing/selftests/powerpc/tm/tm-syscall.c
+++ b/tools/testing/selftests/powerpc/tm/tm-syscall.c
@@ -19,24 +19,37 @@
 #include "utils.h"
 #include "tm.h"
 
+#ifndef PPC_FEATURE2_SCV
+#define PPC_FEATURE2_SCV               0x00100000 /* scv syscall */
+#endif
+
 extern int getppid_tm_active(void);
 extern int getppid_tm_suspended(void);
+extern int getppid_scv_tm_active(void);
+extern int getppid_scv_tm_suspended(void);
 
 unsigned retries = 0;
 
 #define TEST_DURATION 10 /* seconds */
 #define TM_RETRIES 100
 
-pid_t getppid_tm(bool suspend)
+pid_t getppid_tm(bool scv, bool suspend)
 {
 	int i;
 	pid_t pid;
 
 	for (i = 0; i < TM_RETRIES; i++) {
-		if (suspend)
-			pid = getppid_tm_suspended();
-		else
-			pid = getppid_tm_active();
+		if (suspend) {
+			if (scv)
+				pid = getppid_scv_tm_suspended();
+			else
+				pid = getppid_tm_suspended();
+		} else {
+			if (scv)
+				pid = getppid_scv_tm_active();
+			else
+				pid = getppid_tm_active();
+		}
 
 		if (pid >= 0)
 			return pid;
@@ -82,15 +95,24 @@ int tm_syscall(void)
 		 * Test a syscall within a suspended transaction and verify
 		 * that it succeeds.
 		 */
-		FAIL_IF(getppid_tm(true) == -1); /* Should succeed. */
+		FAIL_IF(getppid_tm(false, true) == -1); /* Should succeed. */
 
 		/*
 		 * Test a syscall within an active transaction and verify that
 		 * it fails with the correct failure code.
 		 */
-		FAIL_IF(getppid_tm(false) != -1);  /* Should fail... */
+		FAIL_IF(getppid_tm(false, false) != -1);  /* Should fail... */
 		FAIL_IF(!failure_is_persistent()); /* ...persistently... */
 		FAIL_IF(!failure_is_syscall());    /* ...with code syscall. */
+
+		/* Now do it all again with scv if it is available. */
+		if (have_hwcap2(PPC_FEATURE2_SCV)) {
+			FAIL_IF(getppid_tm(true, true) == -1); /* Should succeed. */
+			FAIL_IF(getppid_tm(true, false) != -1);  /* Should fail... */
+			FAIL_IF(!failure_is_persistent()); /* ...persistently... */
+			FAIL_IF(!failure_is_syscall());    /* ...with code syscall. */
+		}
+
 		gettimeofday(&now, 0);
 	}
 
-- 
2.23.0