rseq/selftests: Add __rseq_exit_point_array section for debuggers

Knowing all exit points is useful to assist debuggers stepping over the
rseq critical sections without requiring them to disassemble the content
of the critical section to figure out the exit points.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Joel Fernandes <joelaf@google.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Dave Watson <davejwatson@fb.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Shuah Khan <shuah@kernel.org>
CC: Andi Kleen <andi@firstfloor.org>
CC: linux-kselftest@vger.kernel.org
CC: "H . Peter Anvin" <hpa@zytor.com>
CC: Chris Lameter <cl@linux.com>
CC: Russell King <linux@arm.linux.org.uk>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
CC: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
CC: Paul Turner <pjt@google.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: Josh Triplett <josh@joshtriplett.org>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Ben Maurer <bmaurer@fb.com>
CC: linux-api@vger.kernel.org
CC: Andy Lutomirski <luto@amacapital.net>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

1 files changed, 52 insertions, 0 deletions

diff --git a/tools/testing/selftests/rseq/rseq-arm.h b/tools/testing/selftests/rseq/rseq-arm.h
index 3cea19877227..17e8d231943a 100644
--- a/tools/testing/selftests/rseq/rseq-arm.h
+++ b/tools/testing/selftests/rseq/rseq-arm.h
@@ -42,6 +42,19 @@ do {									\
 	__RSEQ_ASM_DEFINE_TABLE(0x0, 0x0, start_ip,			\
 				(post_commit_ip - start_ip), abort_ip)
 
+/*
+ * Exit points of a rseq critical section consist of all instructions outside
+ * of the critical section where a critical section can either branch to or
+ * reach through the normal course of its execution. The abort IP and the
+ * post-commit IP are already part of the __rseq_table section and should not
+ * be explicitly defined as additional exit points. Knowing all exit points is
+ * useful to assist debuggers stepping over the critical section.
+ */
+#define RSEQ_ASM_DEFINE_EXIT_POINT(start_ip, exit_ip)			\
+		".pushsection __rseq_exit_point_array, \"aw\"\n\t"	\
+		".word " __rseq_str(start_ip) ", 0x0, " __rseq_str(exit_ip) ", 0x0\n\t" \
+		".popsection\n\t"
+
 #define RSEQ_ASM_STORE_RSEQ_CS(label, cs_label, rseq_cs)		\
 		RSEQ_INJECT_ASM(1)					\
 		"adr r0, " __rseq_str(cs_label) "\n\t"			\
@@ -87,6 +100,11 @@ int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
 	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(1f, 2f, 4f) /* start, commit, abort */
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
+#ifdef RSEQ_COMPARE_TWICE
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error1])
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error2])
+#endif
 		/* Start rseq by storing table entry pointer into rseq_cs. */
 		RSEQ_ASM_STORE_RSEQ_CS(1, 3f, rseq_cs)
 		RSEQ_ASM_CMP_CPU_ID(cpu_id, current_cpu_id, 4f)
@@ -149,6 +167,11 @@ int rseq_cmpnev_storeoffp_load(intptr_t *v, intptr_t expectnot,
 	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(1f, 2f, 4f) /* start, commit, abort */
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
+#ifdef RSEQ_COMPARE_TWICE
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error1])
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error2])
+#endif
 		/* Start rseq by storing table entry pointer into rseq_cs. */
 		RSEQ_ASM_STORE_RSEQ_CS(1, 3f, rseq_cs)
 		RSEQ_ASM_CMP_CPU_ID(cpu_id, current_cpu_id, 4f)
@@ -215,6 +238,9 @@ int rseq_addv(intptr_t *v, intptr_t count, int cpu)
 	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(1f, 2f, 4f) /* start, commit, abort */
+#ifdef RSEQ_COMPARE_TWICE
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error1])
+#endif
 		/* Start rseq by storing table entry pointer into rseq_cs. */
 		RSEQ_ASM_STORE_RSEQ_CS(1, 3f, rseq_cs)
 		RSEQ_ASM_CMP_CPU_ID(cpu_id, current_cpu_id, 4f)
@@ -267,6 +293,11 @@ int rseq_cmpeqv_trystorev_storev(intptr_t *v, intptr_t expect,
 	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(1f, 2f, 4f) /* start, commit, abort */
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
+#ifdef RSEQ_COMPARE_TWICE
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error1])
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error2])
+#endif
 		/* Start rseq by storing table entry pointer into rseq_cs. */
 		RSEQ_ASM_STORE_RSEQ_CS(1, 3f, rseq_cs)
 		RSEQ_ASM_CMP_CPU_ID(cpu_id, current_cpu_id, 4f)
@@ -337,6 +368,11 @@ int rseq_cmpeqv_trystorev_storev_release(intptr_t *v, intptr_t expect,
 	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(1f, 2f, 4f) /* start, commit, abort */
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
+#ifdef RSEQ_COMPARE_TWICE
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error1])
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error2])
+#endif
 		/* Start rseq by storing table entry pointer into rseq_cs. */
 		RSEQ_ASM_STORE_RSEQ_CS(1, 3f, rseq_cs)
 		RSEQ_ASM_CMP_CPU_ID(cpu_id, current_cpu_id, 4f)
@@ -408,6 +444,12 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *v, intptr_t expect,
 	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(1f, 2f, 4f) /* start, commit, abort */
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
+#ifdef RSEQ_COMPARE_TWICE
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error1])
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error2])
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error3])
+#endif
 		/* Start rseq by storing table entry pointer into rseq_cs. */
 		RSEQ_ASM_STORE_RSEQ_CS(1, 3f, rseq_cs)
 		RSEQ_ASM_CMP_CPU_ID(cpu_id, current_cpu_id, 4f)
@@ -486,6 +528,11 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_t *v, intptr_t expect,
 	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(1f, 2f, 4f) /* start, commit, abort */
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
+#ifdef RSEQ_COMPARE_TWICE
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error1])
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error2])
+#endif
 		"str %[src], %[rseq_scratch0]\n\t"
 		"str %[dst], %[rseq_scratch1]\n\t"
 		"str %[len], %[rseq_scratch2]\n\t"
@@ -605,6 +652,11 @@ int rseq_cmpeqv_trymemcpy_storev_release(intptr_t *v, intptr_t expect,
 	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(1f, 2f, 4f) /* start, commit, abort */
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
+#ifdef RSEQ_COMPARE_TWICE
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error1])
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error2])
+#endif
 		"str %[src], %[rseq_scratch0]\n\t"
 		"str %[dst], %[rseq_scratch1]\n\t"
 		"str %[len], %[rseq_scratch2]\n\t"