[RFC PATCH 0/5] RSEQ selftests uplift for glibc-2.35 compatibility

[RFC PATCH 0/5] RSEQ selftests uplift for glibc-2.35 compatibility

[Mathieu Desnoyers]

glibc-2.35 will be released on 2022-02-01. It introduces a user-space ABI
based on the thread pointer to access a reserved area of the TCB.

The rseq selftests originally expected the rseq thread data to sit in a
__rseq_abi TLS variable.

Considering that the rseq ABI only allows a single rseq registration per
thread, both cannot actively coexist in a process.

Adapt the selftests librseq implementation to become compatible with
glibc-2.35. Keep a fallback implementation based on TLS available when
an older glibc is detected.

Feedback is welcome,

Thanks,

Mathieu

Mathieu Desnoyers (5):
  selftests/rseq: Remove useless assignment to cpu variable
  selftests/rseq: Remove volatile from __rseq_abi
  selftests/rseq: Introduce rseq_get_abi() helper
  selftests/rseq: Introduce thread pointer getters
  selftests/rseq: Uplift rseq selftests for compatibility with
    glibc-2.35

 tools/testing/selftests/rseq/Makefile         |   2 +-
 tools/testing/selftests/rseq/param_test.c     |   4 +-
 tools/testing/selftests/rseq/rseq-arm.h       |  32 ++--
 tools/testing/selftests/rseq/rseq-arm64.h     |  32 ++--
 .../rseq/rseq-generic-thread-pointer.h        |  25 +++
 tools/testing/selftests/rseq/rseq-mips.h      |  32 ++--
 .../selftests/rseq/rseq-ppc-thread-pointer.h  |  30 ++++
 tools/testing/selftests/rseq/rseq-ppc.h       |  32 ++--
 tools/testing/selftests/rseq/rseq-s390.h      |  24 +--
 .../selftests/rseq/rseq-thread-pointer.h      |  19 +++
 .../selftests/rseq/rseq-x86-thread-pointer.h  |  40 +++++
 tools/testing/selftests/rseq/rseq-x86.h       |  30 ++--
 tools/testing/selftests/rseq/rseq.c           | 161 +++++++++---------
 tools/testing/selftests/rseq/rseq.h           |  24 ++-
 14 files changed, 302 insertions(+), 185 deletions(-)
 create mode 100644 tools/testing/selftests/rseq/rseq-generic-thread-pointer.h
 create mode 100644 tools/testing/selftests/rseq/rseq-ppc-thread-pointer.h
 create mode 100644 tools/testing/selftests/rseq/rseq-thread-pointer.h
 create mode 100644 tools/testing/selftests/rseq/rseq-x86-thread-pointer.h

-- 
2.17.1

[RFC PATCH 1/5] selftests/rseq: Remove useless assignment to cpu variable

[Mathieu Desnoyers]

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 tools/testing/selftests/rseq/param_test.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/tools/testing/selftests/rseq/param_test.c b/tools/testing/selftests/rseq/param_test.c
index 699ad5f93c34..cc2cfc1da938 100644
--- a/tools/testing/selftests/rseq/param_test.c
+++ b/tools/testing/selftests/rseq/param_test.c
@@ -368,9 +368,7 @@ void *test_percpu_spinlock_thread(void *arg)
 		abort();
 	reps = thread_data->reps;
 	for (i = 0; i < reps; i++) {
-		int cpu = rseq_cpu_start();
-
-		cpu = rseq_this_cpu_lock(&data->lock);
+		int cpu = rseq_this_cpu_lock(&data->lock);
 		data->c[cpu].count++;
 		rseq_percpu_unlock(&data->lock, cpu);
 #ifndef BENCHMARK
-- 
2.17.1

[RFC PATCH 2/5] selftests/rseq: Remove volatile from __rseq_abi

[Mathieu Desnoyers]

This is done in preparation for the selftest uplift to become compatible
with glibc-2.35.

All accesses to the __rseq_abi fields are volatile, but remove the
volatile from the TLS variable declaration, otherwise we are stuck with
volatile for the upcoming rseq_get_abi() helper.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 tools/testing/selftests/rseq/rseq.c | 4 ++--
 tools/testing/selftests/rseq/rseq.h | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
index 7159eb777fd3..a0d8eed24035 100644
--- a/tools/testing/selftests/rseq/rseq.c
+++ b/tools/testing/selftests/rseq/rseq.c
@@ -31,7 +31,7 @@
 
 #define ARRAY_SIZE(arr)	(sizeof(arr) / sizeof((arr)[0]))
 
-__thread volatile struct rseq __rseq_abi = {
+__thread struct rseq __rseq_abi = {
 	.cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
 };
 
@@ -93,7 +93,7 @@ int rseq_register_current_thread(void)
 		goto end;
 	}
 	if (errno != EBUSY)
-		__rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
+		RSEQ_WRITE_ONCE(__rseq_abi.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
 	ret = -1;
 	__rseq_refcount--;
 end:
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
index 3f63eb362b92..f971a9217145 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -43,7 +43,7 @@
 #define RSEQ_INJECT_FAILED
 #endif
 
-extern __thread volatile struct rseq __rseq_abi;
+extern __thread struct rseq __rseq_abi;
 extern int __rseq_handled;
 
 #define rseq_likely(x)		__builtin_expect(!!(x), 1)
@@ -140,9 +140,9 @@ static inline uint32_t rseq_current_cpu(void)
 static inline void rseq_clear_rseq_cs(void)
 {
 #ifdef __LP64__
-	__rseq_abi.rseq_cs.ptr = 0;
+	RSEQ_WRITE_ONCE(__rseq_abi.rseq_cs.ptr, 0);
 #else
-	__rseq_abi.rseq_cs.ptr.ptr32 = 0;
+	RSEQ_WRITE_ONCE(__rseq_abi.rseq_cs.ptr.ptr32, 0);
 #endif
 }
 
-- 
2.17.1

[RFC PATCH 3/5] selftests/rseq: Introduce rseq_get_abi() helper

[Mathieu Desnoyers]

This is done in preparation for the selftest uplift to become compatible
with glibc-2.35.

glibc-2.35 exposes the rseq per-thread data in the TCB, accessible
at an offset from the thread pointer, rather than through an actual
Thread-Local Storage (TLS) variable, as the kernel selftests initially
expected.

Introduce a rseq_get_abi() helper, initially using the __rseq_abi
TLS variable, in preparation for changing this userspace ABI for one
which is compatible with glibc-2.35.

Note that the __rseq_abi TLS and glibc-2.35's ABI for per-thread data
cannot actively coexist in a process, because the kernel supports only
a single rseq registration per thread.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 tools/testing/selftests/rseq/rseq-arm.h   | 32 +++++++++++------------
 tools/testing/selftests/rseq/rseq-arm64.h | 32 +++++++++++------------
 tools/testing/selftests/rseq/rseq-mips.h  | 32 +++++++++++------------
 tools/testing/selftests/rseq/rseq-ppc.h   | 32 +++++++++++------------
 tools/testing/selftests/rseq/rseq-s390.h  | 24 ++++++++---------
 tools/testing/selftests/rseq/rseq-x86.h   | 30 ++++++++++-----------
 tools/testing/selftests/rseq/rseq.h       | 13 ++++++---
 7 files changed, 100 insertions(+), 95 deletions(-)

diff --git a/tools/testing/selftests/rseq/rseq-arm.h b/tools/testing/selftests/rseq/rseq-arm.h
index 5943c816c07c..6716540e17c6 100644
--- a/tools/testing/selftests/rseq/rseq-arm.h
+++ b/tools/testing/selftests/rseq/rseq-arm.h
@@ -185,8 +185,8 @@ int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
 		  [newv]		"r" (newv)
@@ -255,8 +255,8 @@ int rseq_cmpnev_storeoffp_load(intptr_t *v, intptr_t expectnot,
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expectnot]		"r" (expectnot),
@@ -316,8 +316,8 @@ int rseq_addv(intptr_t *v, intptr_t count, int cpu)
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [v]			"m" (*v),
 		  [count]		"Ir" (count)
 		  RSEQ_INJECT_INPUT
@@ -381,8 +381,8 @@ int rseq_cmpeqv_trystorev_storev(intptr_t *v, intptr_t expect,
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* try store input */
 		  [v2]			"m" (*v2),
 		  [newv2]		"r" (newv2),
@@ -457,8 +457,8 @@ int rseq_cmpeqv_trystorev_storev_release(intptr_t *v, intptr_t expect,
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* try store input */
 		  [v2]			"m" (*v2),
 		  [newv2]		"r" (newv2),
@@ -537,8 +537,8 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *v, intptr_t expect,
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* cmp2 input */
 		  [v2]			"m" (*v2),
 		  [expect2]		"r" (expect2),
@@ -657,8 +657,8 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_t *v, intptr_t expect,
 		"8:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
@@ -782,8 +782,8 @@ int rseq_cmpeqv_trymemcpy_storev_release(intptr_t *v, intptr_t expect,
 		"8:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
diff --git a/tools/testing/selftests/rseq/rseq-arm64.h b/tools/testing/selftests/rseq/rseq-arm64.h
index 200dae9e4208..b9d9b3aa6e9b 100644
--- a/tools/testing/selftests/rseq/rseq-arm64.h
+++ b/tools/testing/selftests/rseq/rseq-arm64.h
@@ -230,8 +230,8 @@ int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"Qo" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"Qo" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [v]			"Qo" (*v),
 		  [expect]		"r" (expect),
 		  [newv]		"r" (newv)
@@ -287,8 +287,8 @@ int rseq_cmpnev_storeoffp_load(intptr_t *v, intptr_t expectnot,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"Qo" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"Qo" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [v]			"Qo" (*v),
 		  [expectnot]		"r" (expectnot),
 		  [load]		"Qo" (*load),
@@ -337,8 +337,8 @@ int rseq_addv(intptr_t *v, intptr_t count, int cpu)
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"Qo" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"Qo" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [v]			"Qo" (*v),
 		  [count]		"r" (count)
 		  RSEQ_INJECT_INPUT
@@ -388,8 +388,8 @@ int rseq_cmpeqv_trystorev_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"Qo" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"Qo" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [expect]		"r" (expect),
 		  [v]			"Qo" (*v),
 		  [newv]		"r" (newv),
@@ -447,8 +447,8 @@ int rseq_cmpeqv_trystorev_storev_release(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"Qo" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"Qo" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [expect]		"r" (expect),
 		  [v]			"Qo" (*v),
 		  [newv]		"r" (newv),
@@ -508,8 +508,8 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"Qo" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"Qo" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [v]			"Qo" (*v),
 		  [expect]		"r" (expect),
 		  [v2]			"Qo" (*v2),
@@ -569,8 +569,8 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"Qo" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"Qo" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [expect]		"r" (expect),
 		  [v]			"Qo" (*v),
 		  [newv]		"r" (newv),
@@ -629,8 +629,8 @@ int rseq_cmpeqv_trymemcpy_storev_release(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"Qo" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"Qo" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [expect]		"r" (expect),
 		  [v]			"Qo" (*v),
 		  [newv]		"r" (newv),
diff --git a/tools/testing/selftests/rseq/rseq-mips.h b/tools/testing/selftests/rseq/rseq-mips.h
index e989e7c14b09..2b1f5bd95268 100644
--- a/tools/testing/selftests/rseq/rseq-mips.h
+++ b/tools/testing/selftests/rseq/rseq-mips.h
@@ -190,8 +190,8 @@ int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
 		  [newv]		"r" (newv)
@@ -258,8 +258,8 @@ int rseq_cmpnev_storeoffp_load(intptr_t *v, intptr_t expectnot,
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expectnot]		"r" (expectnot),
@@ -319,8 +319,8 @@ int rseq_addv(intptr_t *v, intptr_t count, int cpu)
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [v]			"m" (*v),
 		  [count]		"Ir" (count)
 		  RSEQ_INJECT_INPUT
@@ -382,8 +382,8 @@ int rseq_cmpeqv_trystorev_storev(intptr_t *v, intptr_t expect,
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* try store input */
 		  [v2]			"m" (*v2),
 		  [newv2]		"r" (newv2),
@@ -456,8 +456,8 @@ int rseq_cmpeqv_trystorev_storev_release(intptr_t *v, intptr_t expect,
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* try store input */
 		  [v2]			"m" (*v2),
 		  [newv2]		"r" (newv2),
@@ -532,8 +532,8 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *v, intptr_t expect,
 		"5:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* cmp2 input */
 		  [v2]			"m" (*v2),
 		  [expect2]		"r" (expect2),
@@ -649,8 +649,8 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_t *v, intptr_t expect,
 		"8:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
@@ -771,8 +771,8 @@ int rseq_cmpeqv_trymemcpy_storev_release(intptr_t *v, intptr_t expect,
 		"8:\n\t"
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
diff --git a/tools/testing/selftests/rseq/rseq-ppc.h b/tools/testing/selftests/rseq/rseq-ppc.h
index 76be90196fe4..2e6b7572ba08 100644
--- a/tools/testing/selftests/rseq/rseq-ppc.h
+++ b/tools/testing/selftests/rseq/rseq-ppc.h
@@ -235,8 +235,8 @@ int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
 		  [newv]		"r" (newv)
@@ -301,8 +301,8 @@ int rseq_cmpnev_storeoffp_load(intptr_t *v, intptr_t expectnot,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expectnot]		"r" (expectnot),
@@ -359,8 +359,8 @@ int rseq_addv(intptr_t *v, intptr_t count, int cpu)
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [count]		"r" (count)
@@ -419,8 +419,8 @@ int rseq_cmpeqv_trystorev_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* try store input */
 		  [v2]			"m" (*v2),
 		  [newv2]		"r" (newv2),
@@ -489,8 +489,8 @@ int rseq_cmpeqv_trystorev_storev_release(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* try store input */
 		  [v2]			"m" (*v2),
 		  [newv2]		"r" (newv2),
@@ -560,8 +560,8 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* cmp2 input */
 		  [v2]			"m" (*v2),
 		  [expect2]		"r" (expect2),
@@ -635,8 +635,8 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
@@ -711,8 +711,8 @@ int rseq_cmpeqv_trymemcpy_storev_release(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
diff --git a/tools/testing/selftests/rseq/rseq-s390.h b/tools/testing/selftests/rseq/rseq-s390.h
index 8ef94ad1cbb4..b906e044d2a3 100644
--- a/tools/testing/selftests/rseq/rseq-s390.h
+++ b/tools/testing/selftests/rseq/rseq-s390.h
@@ -165,8 +165,8 @@ int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
 		  [newv]		"r" (newv)
@@ -233,8 +233,8 @@ int rseq_cmpnev_storeoffp_load(intptr_t *v, intptr_t expectnot,
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expectnot]		"r" (expectnot),
@@ -288,8 +288,8 @@ int rseq_addv(intptr_t *v, intptr_t count, int cpu)
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [count]		"r" (count)
@@ -347,8 +347,8 @@ int rseq_cmpeqv_trystorev_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* try store input */
 		  [v2]			"m" (*v2),
 		  [newv2]		"r" (newv2),
@@ -426,8 +426,8 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* cmp2 input */
 		  [v2]			"m" (*v2),
 		  [expect2]		"r" (expect2),
@@ -534,8 +534,8 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_t *v, intptr_t expect,
 #endif
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [current_cpu_id]	"m" (__rseq_abi.cpu_id),
-		  [rseq_cs]		"m" (__rseq_abi.rseq_cs),
+		  [current_cpu_id]	"m" (rseq_get_abi()->cpu_id),
+		  [rseq_cs]		"m" (rseq_get_abi()->rseq_cs),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
diff --git a/tools/testing/selftests/rseq/rseq-x86.h b/tools/testing/selftests/rseq/rseq-x86.h
index 640411518e46..1d9fa0516e53 100644
--- a/tools/testing/selftests/rseq/rseq-x86.h
+++ b/tools/testing/selftests/rseq/rseq-x86.h
@@ -141,7 +141,7 @@ int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
 		  [newv]		"r" (newv)
@@ -207,7 +207,7 @@ int rseq_cmpnev_storeoffp_load(intptr_t *v, intptr_t expectnot,
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expectnot]		"r" (expectnot),
@@ -258,7 +258,7 @@ int rseq_addv(intptr_t *v, intptr_t count, int cpu)
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [count]		"er" (count)
@@ -314,7 +314,7 @@ int rseq_offset_deref_addv(intptr_t *ptr, off_t off, intptr_t inc, int cpu)
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* final store input */
 		  [ptr]			"m" (*ptr),
 		  [off]			"er" (off),
@@ -372,7 +372,7 @@ int rseq_cmpeqv_trystorev_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* try store input */
 		  [v2]			"m" (*v2),
 		  [newv2]		"r" (newv2),
@@ -449,7 +449,7 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* cmp2 input */
 		  [v2]			"m" (*v2),
 		  [expect2]		"r" (expect2),
@@ -555,7 +555,7 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_t *v, intptr_t expect,
 #endif
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
@@ -719,7 +719,7 @@ int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  [v]			"m" (*v),
 		  [expect]		"r" (expect),
 		  [newv]		"r" (newv)
@@ -785,7 +785,7 @@ int rseq_cmpnev_storeoffp_load(intptr_t *v, intptr_t expectnot,
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expectnot]		"r" (expectnot),
@@ -836,7 +836,7 @@ int rseq_addv(intptr_t *v, intptr_t count, int cpu)
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [count]		"ir" (count)
@@ -894,7 +894,7 @@ int rseq_cmpeqv_trystorev_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* try store input */
 		  [v2]			"m" (*v2),
 		  [newv2]		"m" (newv2),
@@ -962,7 +962,7 @@ int rseq_cmpeqv_trystorev_storev_release(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* try store input */
 		  [v2]			"m" (*v2),
 		  [newv2]		"r" (newv2),
@@ -1032,7 +1032,7 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *v, intptr_t expect,
 		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* cmp2 input */
 		  [v2]			"m" (*v2),
 		  [expect2]		"r" (expect2),
@@ -1142,7 +1142,7 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_t *v, intptr_t expect,
 #endif
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expect]		"m" (expect),
@@ -1255,7 +1255,7 @@ int rseq_cmpeqv_trymemcpy_storev_release(intptr_t *v, intptr_t expect,
 #endif
 		: /* gcc asm goto does not allow outputs */
 		: [cpu_id]		"r" (cpu),
-		  [rseq_abi]		"r" (&__rseq_abi),
+		  [rseq_abi]		"r" (rseq_get_abi()),
 		  /* final store input */
 		  [v]			"m" (*v),
 		  [expect]		"m" (expect),
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
index f971a9217145..3e7b5c54ab3d 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -46,6 +46,11 @@
 extern __thread struct rseq __rseq_abi;
 extern int __rseq_handled;
 
+static inline struct rseq *rseq_get_abi(void)
+{
+	return &__rseq_abi;
+}
+
 #define rseq_likely(x)		__builtin_expect(!!(x), 1)
 #define rseq_unlikely(x)	__builtin_expect(!!(x), 0)
 #define rseq_barrier()		__asm__ __volatile__("" : : : "memory")
@@ -108,7 +113,7 @@ int32_t rseq_fallback_current_cpu(void);
  */
 static inline int32_t rseq_current_cpu_raw(void)
 {
-	return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id);
+	return RSEQ_ACCESS_ONCE(rseq_get_abi()->cpu_id);
 }
 
 /*
@@ -124,7 +129,7 @@ static inline int32_t rseq_current_cpu_raw(void)
  */
 static inline uint32_t rseq_cpu_start(void)
 {
-	return RSEQ_ACCESS_ONCE(__rseq_abi.cpu_id_start);
+	return RSEQ_ACCESS_ONCE(rseq_get_abi()->cpu_id_start);
 }
 
 static inline uint32_t rseq_current_cpu(void)
@@ -140,9 +145,9 @@ static inline uint32_t rseq_current_cpu(void)
 static inline void rseq_clear_rseq_cs(void)
 {
 #ifdef __LP64__
-	RSEQ_WRITE_ONCE(__rseq_abi.rseq_cs.ptr, 0);
+	RSEQ_WRITE_ONCE(rseq_get_abi()->rseq_cs.ptr, 0);
 #else
-	RSEQ_WRITE_ONCE(__rseq_abi.rseq_cs.ptr.ptr32, 0);
+	RSEQ_WRITE_ONCE(rseq_get_abi()->rseq_cs.ptr.ptr32, 0);
 #endif
 }
 
-- 
2.17.1

[RFC PATCH 4/5] selftests/rseq: Introduce thread pointer getters

[Mathieu Desnoyers]

This is done in preparation for the selftest uplift to become compatible
with glibc-2.35.

glibc-2.35 exposes the rseq per-thread data in the TCB, accessible
at an offset from the thread pointer.

The toolchains do not implement accessing the thread pointer on all
architectures. Provide thread pointer getters for ppc and x86 which
lack (or lacked until recently) toolchain support.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 .../rseq/rseq-generic-thread-pointer.h        | 25 ++++++++++++
 .../selftests/rseq/rseq-ppc-thread-pointer.h  | 30 ++++++++++++++
 .../selftests/rseq/rseq-thread-pointer.h      | 19 +++++++++
 .../selftests/rseq/rseq-x86-thread-pointer.h  | 40 +++++++++++++++++++
 4 files changed, 114 insertions(+)
 create mode 100644 tools/testing/selftests/rseq/rseq-generic-thread-pointer.h
 create mode 100644 tools/testing/selftests/rseq/rseq-ppc-thread-pointer.h
 create mode 100644 tools/testing/selftests/rseq/rseq-thread-pointer.h
 create mode 100644 tools/testing/selftests/rseq/rseq-x86-thread-pointer.h

diff --git a/tools/testing/selftests/rseq/rseq-generic-thread-pointer.h b/tools/testing/selftests/rseq/rseq-generic-thread-pointer.h
new file mode 100644
index 000000000000..38c584661571
--- /dev/null
+++ b/tools/testing/selftests/rseq/rseq-generic-thread-pointer.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: LGPL-2.1-only OR MIT */
+/*
+ * rseq-generic-thread-pointer.h
+ *
+ * (C) Copyright 2021 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#ifndef _RSEQ_GENERIC_THREAD_POINTER
+#define _RSEQ_GENERIC_THREAD_POINTER
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Use gcc builtin thread pointer. */
+static inline void *rseq_thread_pointer(void)
+{
+	return __builtin_thread_pointer();
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/tools/testing/selftests/rseq/rseq-ppc-thread-pointer.h b/tools/testing/selftests/rseq/rseq-ppc-thread-pointer.h
new file mode 100644
index 000000000000..263eee84fb76
--- /dev/null
+++ b/tools/testing/selftests/rseq/rseq-ppc-thread-pointer.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: LGPL-2.1-only OR MIT */
+/*
+ * rseq-ppc-thread-pointer.h
+ *
+ * (C) Copyright 2021 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#ifndef _RSEQ_PPC_THREAD_POINTER
+#define _RSEQ_PPC_THREAD_POINTER
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static inline void *rseq_thread_pointer(void)
+{
+#ifdef __powerpc64__
+	register void *__result asm ("r13");
+#else
+	register void *__result asm ("r2");
+#endif
+	asm ("" : "=r" (__result));
+	return __result;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/tools/testing/selftests/rseq/rseq-thread-pointer.h b/tools/testing/selftests/rseq/rseq-thread-pointer.h
new file mode 100644
index 000000000000..977c25d758b2
--- /dev/null
+++ b/tools/testing/selftests/rseq/rseq-thread-pointer.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: LGPL-2.1-only OR MIT */
+/*
+ * rseq-thread-pointer.h
+ *
+ * (C) Copyright 2021 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#ifndef _RSEQ_THREAD_POINTER
+#define _RSEQ_THREAD_POINTER
+
+#if defined(__x86_64__) || defined(__i386__)
+#include "rseq-x86-thread-pointer.h"
+#elif defined(__PPC__)
+#include "rseq-ppc-thread-pointer.h"
+#else
+#include "rseq-generic-thread-pointer.h"
+#endif
+
+#endif
diff --git a/tools/testing/selftests/rseq/rseq-x86-thread-pointer.h b/tools/testing/selftests/rseq/rseq-x86-thread-pointer.h
new file mode 100644
index 000000000000..d3133587d996
--- /dev/null
+++ b/tools/testing/selftests/rseq/rseq-x86-thread-pointer.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: LGPL-2.1-only OR MIT */
+/*
+ * rseq-x86-thread-pointer.h
+ *
+ * (C) Copyright 2021 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#ifndef _RSEQ_X86_THREAD_POINTER
+#define _RSEQ_X86_THREAD_POINTER
+
+#include <features.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#if __GNUC_PREREQ (11, 1)
+static inline void *rseq_thread_pointer(void)
+{
+	return __builtin_thread_pointer();
+}
+#else
+static inline void *rseq_thread_pointer(void)
+{
+	void *__result;
+
+# ifdef __x86_64__
+	__asm__ ("mov %%fs:0, %0" : "=r" (__result));
+# else
+	__asm__ ("mov %%gs:0, %0" : "=r" (__result));
+# endif
+	return __result;
+}
+#endif /* !GCC 11 */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
-- 
2.17.1

[RFC PATCH 5/5] selftests/rseq: Uplift rseq selftests for compatibility with glibc-2.35

[Mathieu Desnoyers]

glibc-2.35 (upcoming release date 2022-02-01) exposes the rseq per-thread
data in the TCB, accessible at an offset from the thread pointer, rather
than through an actual Thread-Local Storage (TLS) variable, as the
Linux kernel selftests initially expected.

The __rseq_abi TLS and glibc-2.35's ABI for per-thread data cannot
actively coexist in a process, because the kernel supports only a single
rseq registration per thread.

Here is the scheme introduced to ensure selftests can work both with an
older glibc and with glibc-2.35+:

- librseq exposes its own "rseq_offset, rseq_size, rseq_flags" ABI.

- librseq queries for glibc rseq ABI (__rseq_offset, __rseq_size,
  __rseq_flags) using dlsym() in a librseq library constructor. If those
  are found, copy their values into rseq_offset, rseq_size, and
  rseq_flags.

- Else, if those glibc symbols are not found, handle rseq registration
  from librseq and use its own IE-model TLS to implement the rseq ABI
  per-thread storage.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 tools/testing/selftests/rseq/Makefile |   2 +-
 tools/testing/selftests/rseq/rseq.c   | 161 ++++++++++++--------------
 tools/testing/selftests/rseq/rseq.h   |  13 ++-
 3 files changed, 88 insertions(+), 88 deletions(-)

diff --git a/tools/testing/selftests/rseq/Makefile b/tools/testing/selftests/rseq/Makefile
index 2af9d39a9716..215e1067f037 100644
--- a/tools/testing/selftests/rseq/Makefile
+++ b/tools/testing/selftests/rseq/Makefile
@@ -6,7 +6,7 @@ endif
 
 CFLAGS += -O2 -Wall -g -I./ -I../../../../usr/include/ -L$(OUTPUT) -Wl,-rpath=./ \
 	  $(CLANG_FLAGS)
-LDLIBS += -lpthread
+LDLIBS += -lpthread -ldl
 
 # Own dependencies because we only want to build against 1st prerequisite, but
 # still track changes to header files and depend on shared object.
diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
index a0d8eed24035..a3e2815f0002 100644
--- a/tools/testing/selftests/rseq/rseq.c
+++ b/tools/testing/selftests/rseq/rseq.c
@@ -26,131 +26,124 @@
 #include <assert.h>
 #include <signal.h>
 #include <limits.h>
+#include <dlfcn.h>
 
 #include "rseq.h"
 
 #define ARRAY_SIZE(arr)	(sizeof(arr) / sizeof((arr)[0]))
 
-__thread struct rseq __rseq_abi = {
-	.cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
-};
+static const int *libc_rseq_offset_p;
+static const unsigned int *libc_rseq_size_p;
+static const unsigned int *libc_rseq_flags_p;
 
-/*
- * Shared with other libraries. This library may take rseq ownership if it is
- * still 0 when executing the library constructor. Set to 1 by library
- * constructor when handling rseq. Set to 0 in destructor if handling rseq.
- */
-int __rseq_handled;
+/* Offset from the thread pointer to the rseq area.  */
+int rseq_offset;
+
+/* Size of the registered rseq area.  0 if the registration was
+   unsuccessful.  */
+unsigned int rseq_size = -1U;
+
+/* Flags used during rseq registration.  */
+unsigned int rseq_flags;
 
-/* Whether this library have ownership of rseq registration. */
 static int rseq_ownership;
 
-static __thread volatile uint32_t __rseq_refcount;
+static
+__thread struct rseq __rseq_abi __attribute__((tls_model("initial-exec"))) = {
+	.cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
+};
 
-static void signal_off_save(sigset_t *oldset)
+static int sys_rseq(struct rseq *rseq_abi, uint32_t rseq_len,
+		    int flags, uint32_t sig)
 {
-	sigset_t set;
-	int ret;
-
-	sigfillset(&set);
-	ret = pthread_sigmask(SIG_BLOCK, &set, oldset);
-	if (ret)
-		abort();
+	return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig);
 }
 
-static void signal_restore(sigset_t oldset)
+int rseq_available(void)
 {
-	int ret;
+	int rc;
 
-	ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
-	if (ret)
+	rc = sys_rseq(NULL, 0, 0, 0);
+	if (rc != -1)
 		abort();
-}
-
-static int sys_rseq(volatile struct rseq *rseq_abi, uint32_t rseq_len,
-		    int flags, uint32_t sig)
-{
-	return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig);
+	switch (errno) {
+	case ENOSYS:
+		return 0;
+	case EINVAL:
+		return 1;
+	default:
+		abort();
+	}
 }
 
 int rseq_register_current_thread(void)
 {
-	int rc, ret = 0;
-	sigset_t oldset;
+	int rc;
 
-	if (!rseq_ownership)
+	if (!rseq_ownership) {
+		/* Treat libc's ownership as a successful registration. */
 		return 0;
-	signal_off_save(&oldset);
-	if (__rseq_refcount == UINT_MAX) {
-		ret = -1;
-		goto end;
 	}
-	if (__rseq_refcount++)
-		goto end;
 	rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), 0, RSEQ_SIG);
-	if (!rc) {
-		assert(rseq_current_cpu_raw() >= 0);
-		goto end;
-	}
-	if (errno != EBUSY)
-		RSEQ_WRITE_ONCE(__rseq_abi.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
-	ret = -1;
-	__rseq_refcount--;
-end:
-	signal_restore(oldset);
-	return ret;
+	if (rc)
+		return -1;
+	assert(rseq_current_cpu_raw() >= 0);
+	return 0;
 }
 
 int rseq_unregister_current_thread(void)
 {
-	int rc, ret = 0;
-	sigset_t oldset;
+	int rc;
 
-	if (!rseq_ownership)
+	if (!rseq_ownership) {
+		/* Treat libc's ownership as a successful unregistration. */
 		return 0;
-	signal_off_save(&oldset);
-	if (!__rseq_refcount) {
-		ret = -1;
-		goto end;
 	}
-	if (--__rseq_refcount)
-		goto end;
-	rc = sys_rseq(&__rseq_abi, sizeof(struct rseq),
-		      RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
-	if (!rc)
-		goto end;
-	__rseq_refcount = 1;
-	ret = -1;
-end:
-	signal_restore(oldset);
-	return ret;
+	rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
+	if (rc)
+		return -1;
+	return 0;
 }
 
-int32_t rseq_fallback_current_cpu(void)
+static __attribute__((constructor))
+void rseq_init(void)
 {
-	int32_t cpu;
-
-	cpu = sched_getcpu();
-	if (cpu < 0) {
-		perror("sched_getcpu()");
-		abort();
+	libc_rseq_offset_p = dlsym(RTLD_NEXT, "__rseq_offset");
+	libc_rseq_size_p = dlsym(RTLD_NEXT, "__rseq_size");
+	libc_rseq_flags_p = dlsym(RTLD_NEXT, "__rseq_flags");
+	if (libc_rseq_size_p && libc_rseq_offset_p && libc_rseq_flags_p) {
+		/* rseq registration owned by glibc */
+		rseq_offset = *libc_rseq_offset_p;
+		rseq_size = *libc_rseq_size_p;
+		rseq_flags = *libc_rseq_flags_p;
+		return;
 	}
-	return cpu;
-}
-
-void __attribute__((constructor)) rseq_init(void)
-{
-	/* Check whether rseq is handled by another library. */
-	if (__rseq_handled)
+	if (!rseq_available())
 		return;
-	__rseq_handled = 1;
 	rseq_ownership = 1;
+	rseq_offset = (void *)&__rseq_abi - rseq_thread_pointer();
+	rseq_size = sizeof(struct rseq);
+	rseq_flags = 0;
 }
 
-void __attribute__((destructor)) rseq_fini(void)
+static __attribute__((destructor))
+void rseq_exit(void)
 {
 	if (!rseq_ownership)
 		return;
-	__rseq_handled = 0;
+	rseq_offset = 0;
+	rseq_size = -1U;
 	rseq_ownership = 0;
 }
+
+int32_t rseq_fallback_current_cpu(void)
+{
+	int32_t cpu;
+
+	cpu = sched_getcpu();
+	if (cpu < 0) {
+		perror("sched_getcpu()");
+		abort();
+	}
+	return cpu;
+}
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
index 3e7b5c54ab3d..f55f91e3d6cb 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -43,12 +43,19 @@
 #define RSEQ_INJECT_FAILED
 #endif
 
-extern __thread struct rseq __rseq_abi;
-extern int __rseq_handled;
+#include "rseq-thread-pointer.h"
+
+/* Offset from the thread pointer to the rseq area.  */
+extern int rseq_offset;
+/* Size of the registered rseq area.  0 if the registration was
+   unsuccessful.  */
+extern unsigned int rseq_size;
+/* Flags used during rseq registration.  */
+extern unsigned int rseq_flags;
 
 static inline struct rseq *rseq_get_abi(void)
 {
-	return &__rseq_abi;
+	return (struct rseq *) ((uintptr_t) rseq_thread_pointer() + rseq_offset);
 }
 
 #define rseq_likely(x)		__builtin_expect(!!(x), 1)
-- 
2.17.1

Re: [RFC PATCH 0/5] RSEQ selftests uplift for glibc-2.35 compatibility

[Mathieu Desnoyers]

[ I should really have CC'd the selftests maintainer and mailing list.
  Adding them in Cc to patch 0/5 to bring this series to their attention. ]

----- On Jan 17, 2022, at 3:39 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:

> glibc-2.35 will be released on 2022-02-01. It introduces a user-space ABI
> based on the thread pointer to access a reserved area of the TCB.
> 
> The rseq selftests originally expected the rseq thread data to sit in a
> __rseq_abi TLS variable.
> 
> Considering that the rseq ABI only allows a single rseq registration per
> thread, both cannot actively coexist in a process.
> 
> Adapt the selftests librseq implementation to become compatible with
> glibc-2.35. Keep a fallback implementation based on TLS available when
> an older glibc is detected.
> 
> Feedback is welcome,
> 
> Thanks,
> 
> Mathieu
> 
> Mathieu Desnoyers (5):
>  selftests/rseq: Remove useless assignment to cpu variable
>  selftests/rseq: Remove volatile from __rseq_abi
>  selftests/rseq: Introduce rseq_get_abi() helper
>  selftests/rseq: Introduce thread pointer getters
>  selftests/rseq: Uplift rseq selftests for compatibility with
>    glibc-2.35
> 
> tools/testing/selftests/rseq/Makefile         |   2 +-
> tools/testing/selftests/rseq/param_test.c     |   4 +-
> tools/testing/selftests/rseq/rseq-arm.h       |  32 ++--
> tools/testing/selftests/rseq/rseq-arm64.h     |  32 ++--
> .../rseq/rseq-generic-thread-pointer.h        |  25 +++
> tools/testing/selftests/rseq/rseq-mips.h      |  32 ++--
> .../selftests/rseq/rseq-ppc-thread-pointer.h  |  30 ++++
> tools/testing/selftests/rseq/rseq-ppc.h       |  32 ++--
> tools/testing/selftests/rseq/rseq-s390.h      |  24 +--
> .../selftests/rseq/rseq-thread-pointer.h      |  19 +++
> .../selftests/rseq/rseq-x86-thread-pointer.h  |  40 +++++
> tools/testing/selftests/rseq/rseq-x86.h       |  30 ++--
> tools/testing/selftests/rseq/rseq.c           | 161 +++++++++---------
> tools/testing/selftests/rseq/rseq.h           |  24 ++-
> 14 files changed, 302 insertions(+), 185 deletions(-)
> create mode 100644 tools/testing/selftests/rseq/rseq-generic-thread-pointer.h
> create mode 100644 tools/testing/selftests/rseq/rseq-ppc-thread-pointer.h
> create mode 100644 tools/testing/selftests/rseq/rseq-thread-pointer.h
> create mode 100644 tools/testing/selftests/rseq/rseq-x86-thread-pointer.h
> 
> --
> 2.17.1

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com