Implements two basic tests of RSEQ functionality.
The first, "basic_test" only asserts that RSEQ works moderately correctly.
E.g. that:
- The CPUID pointer works
- Code infinitely looping within a critical section will eventually be
interrupted.
"basic_percpu_ops_test" is a slightly more "realistic" variant, implementing a
few simple per-cpu operations and testing their correctness. It also includes
a trivial example of user-space may multiplexing the critical section via the
restart handler.
Signed-off-by: Paul Turner <pjt@xxxxxxxxxx>
---
tools/testing/selftests/rseq/Makefile | 15 +
.../testing/selftests/rseq/basic_percpu_ops_test.S | 131 ++++++++++
.../testing/selftests/rseq/basic_percpu_ops_test.c | 250 ++++++++++++++++++++
tools/testing/selftests/rseq/basic_test.c | 76 ++++++
tools/testing/selftests/rseq/rseq.c | 48 ++++
tools/testing/selftests/rseq/rseq.h | 28 ++
6 files changed, 548 insertions(+)
create mode 100644 tools/testing/selftests/rseq/Makefile
create mode 100644 tools/testing/selftests/rseq/basic_percpu_ops_test.S
create mode 100644 tools/testing/selftests/rseq/basic_percpu_ops_test.c
create mode 100644 tools/testing/selftests/rseq/basic_test.c
create mode 100644 tools/testing/selftests/rseq/rseq.c
create mode 100644 tools/testing/selftests/rseq/rseq.h
diff --git a/tools/testing/selftests/rseq/Makefile b/tools/testing/selftests/rseq/Makefile
new file mode 100644
index 0000000..c5a2b47
--- /dev/null
+++ b/tools/testing/selftests/rseq/Makefile
@@ -0,0 +1,15 @@
+CFLAGS += -Wall
+LDFLAGS += -lpthread
+
+TESTS = basic_test basic_percpu_ops_test
+
+basic_percpu_ops_test: basic_percpu_ops_test.c basic_percpu_ops_test.S
+
+all: $(TESTS)
+%: %.c
+ $(CC) $(CFLAGS) -o $@ $^ rseq.c $(LDFLAGS)
+
+include ../lib.mk
+
+clean:
+ $(RM) $(TESTS)
diff --git a/tools/testing/selftests/rseq/basic_percpu_ops_test.S b/tools/testing/selftests/rseq/basic_percpu_ops_test.S
new file mode 100644
index 0000000..7da7781
--- /dev/null
+++ b/tools/testing/selftests/rseq/basic_percpu_ops_test.S
@@ -0,0 +1,131 @@
+#include "rseq.h"
+
+#ifdef __x86_64__
+ .text
+ .code64
+
+#define FETCH_CPU(dest) movl %fs:__rseq_current_cpu@TPOFF, dest
+#define CRITICAL_SECTION_OFFSET(label) $label
+
+/* If start <= %RESTART_ADDR_REG < %end, jump to jump_to */
+#define HANDLE_REGION(start, end, jump_to) \
+ cmpq CRITICAL_SECTION_OFFSET(end), %RESTART_ADDR_REG; \
+ jge 1f; \
+ cmpq CRITICAL_SECTION_OFFSET(start), %RESTART_ADDR_REG; \
+ jge jump_to; \
+ 1:;
+
+#define HANDLE_REGION_PREFIX(prefix, start, end, jump_to) \
+ HANDLE_REGION(prefix##start, prefix##end, prefix##jump_to)
+
+/*-----------------------------------------------------------------------------
+ * Start of actual restartable sequences.
+ *---------------------------------------------------------------------------*/
+ .align 8
+ .globl RSEQ_CRITICAL_SECTION_START
+RSEQ_CRITICAL_SECTION_START:
+/* int rseq_percpu_lock() */
+ .globl rseq_percpu_lock
+ .type rseq_percpu_lock, @function
+rseq_percpu_lock:
+ .cfi_startproc
+rseq_percpu_lock_region0:
+ FETCH_CPU(%eax)
+ leaq (,%eax,8), %RESTART_ADDR_REG
+ leaq (%rdi,%RESTART_ADDR_REG,8), %RESTART_ADDR_REG
+rseq_percpu_lock_retry:
+ cmpw $0, (%RESTART_ADDR_REG)
+ jne rseq_percpu_lock_retry
+ movw $1, (%RESTART_ADDR_REG) /* 1 => lock owned */
+rseq_percpu_lock_region1:
+ ret
+rseq_percpu_lock_region2:
+ .cfi_endproc
+
+/*
+ * int rseq_cmpxchg(int cpu, intptr_t *p, intptr_t old, intptr_t new)
+ * int rseq_percpu_cmpxchgcheck(int cpu, intptr_t *p,
+ * intptr_t old, intptr_t new,
+ * intptr_t *check_ptr, intptr_t check_val)
+ *
+ * NOTE: We don't use cmpxchg in the implementation below as that would make
+ * checking the success of our commit operation was dependent on flags (which
+ * are in turn clobbered by the restart region) -- furthermore we can't just
+ * retry to fill in the flags since the restarted cmpxchg may have actually
+ * succeeded; spuriously failing subsequent attempts.
+ */
+
+ .globl rseq_percpu_cmpxchg
+ .type rseq_percpu_cmpxchg, @function
+rseq_percpu_cmpxchg:
+ .cfi_startproc
+rseq_percpu_cmpxchg_region0:
+ FETCH_CPU(%eax)
+ cmp %eax, %edi /* check cpu vs current_cpu */
+ jne rseq_percpu_cmpxchg_region1
+ cmp %rdx, (%rsi) /* verify *p == old */
+ jne rseq_percpu_cmpxchg_region2
+ mov %rcx, (%rsi)
+rseq_percpu_cmpxchg_region1:
+ ret /* return current cpu, indicating mismatch OR success */
+rseq_percpu_cmpxchg_region2:
+ mov $-1, %eax /* mismatch versus "old" or "check", return -1 */
+ ret
+rseq_percpu_cmpxchg_region3:
+ .cfi_endproc
+
+ .globl rseq_percpu_cmpxchgcheck
+ .type rseq_percpu_cmpxchgcheck, @function
+rseq_percpu_cmpxchgcheck:
+ .cfi_startproc
+rseq_percpu_cmpxchgcheck_region0:
+ FETCH_CPU(%eax)
+ cmp %eax, %edi /* check cpu vs current_cpu */
+ jne rseq_percpu_cmpxchgcheck_region1
+ cmp %rdx, (%rsi) /* verify *p == old */
+ jne rseq_percpu_cmpxchgcheck_region2
+ cmp %r9, (%r8) /* verify *check_ptr == check_val */
+ jne rseq_percpu_cmpxchgcheck_region2
+ mov %rcx, (%rsi)
+rseq_percpu_cmpxchgcheck_region1:
+ ret /* return current cpu, indicating mismatch OR success */
+rseq_percpu_cmpxchgcheck_region2:
+ mov $-1, %eax /* mismatch versus "old" or "check", return -1 */
+ ret
+rseq_percpu_cmpxchgcheck_region3:
+ .cfi_endproc
+
+ .align 8
+ .globl RSEQ_CRITICAL_SECTION_END
+RSEQ_CRITICAL_SECTION_END:
+
+/*-----------------------------------------------------------------------------
+ * Restart handler
+ * NOTE: per ABI, %RESTART_ADDR_REG is the program-counter we were restarted at.
+ *----------------------------------------------------------------------------
+ */
+
+ .align 8
+ .globl RSEQ_RESTART_HANDLER
+ .type RSEQ_RESTART_HANDLER, @function
+RSEQ_RESTART_HANDLER:
+ .cfi_startproc
+ /* There are several ways to implement this more efficiently. */
+ HANDLE_REGION_PREFIX(rseq_percpu_lock_region, 0, 1, 0)
+ HANDLE_REGION_PREFIX(rseq_percpu_lock_region, 1, 2, 1)
+
+ HANDLE_REGION_PREFIX(rseq_percpu_cmpxchg_region, 0, 1, 0)
+ HANDLE_REGION_PREFIX(rseq_percpu_cmpxchg_region, 1, 2, 1)
+ HANDLE_REGION_PREFIX(rseq_percpu_cmpxchg_region, 2, 3, 2)
+
+ HANDLE_REGION_PREFIX(rseq_percpu_cmpxchgcheck_region, 0, 1, 0)
+ HANDLE_REGION_PREFIX(rseq_percpu_cmpxchgcheck_region, 1, 2, 1)
+ HANDLE_REGION_PREFIX(rseq_percpu_cmpxchgcheck_region, 2, 3, 2)
+rseq_unknown_restart_addr:
+ mov %RESTART_ADDR_REG, %rdi
+ call rseq_unknown_restart_addr@PLT
+ .cfi_endproc
+
+/* Don't need/want an executable stack. */
+.section .note.GNU-stack,"",@progbits
+#endif
diff --git a/tools/testing/selftests/rseq/basic_percpu_ops_test.c b/tools/testing/selftests/rseq/basic_percpu_ops_test.c
new file mode 100644
index 0000000..c6d7e4e
--- /dev/null
+++ b/tools/testing/selftests/rseq/basic_percpu_ops_test.c
@@ -0,0 +1,250 @@
+#define _GNU_SOURCE
+#include <assert.h>
+#include <pthread.h>
+#include <sched.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "rseq.h"
+
+/* We restrict on !__PIC__ as it greatly simplifies handling of TLS. */
+#if defined(__x86_64__) && !defined(__PIC__)
+
+#define barrier() __asm__ __volatile__("": : :"memory")
+
+/* Implemented by percpu_ops.S */
+struct percpu_lock {
+ int word[CPU_SETSIZE][16]; /* cache aligned; lock-word is [cpu][0] */
+};
+
+/* A simple percpu spinlock. Returns the cpu lock was acquired on. */
+int rseq_percpu_lock(struct percpu_lock *lock);
+
+/*
+ * cmpxchg [with an additional check value].
+ *
+ * Returns:
+ * -1 if *p != old [ || check_ptr != check_val, ] otherwise
+ * cpu that rseq_percpu_cmpxchgcheck was executed.
+ * - If this is different from the passed cpu, no modifications were made.
+ *
+ * Note: When specified, check_ptr is dereferenced iff *p == old
+ */
+int rseq_percpu_cmpxchg(int cpu, intptr_t *p, intptr_t old, intptr_t new);
+int rseq_percpu_cmpxchgcheck(int cpu, intptr_t *p, intptr_t old, intptr_t new,
+ intptr_t *check_ptr, intptr_t check_val);
+
+
+void rseq_percpu_unlock(struct percpu_lock *lock, int cpu)
+{
+ barrier(); /* need a release-store here, this suffices on x86. */
+ assert(lock->word[cpu][0] == 1);
+ lock->word[cpu][0] = 0;
+}
+
+void rseq_unknown_restart_addr(void *addr)
+{
+ fprintf(stderr, "rseq: unrecognized restart address %p\n", addr);
+ exit(1);
+}
+
+struct spinlock_test_data {
+ struct percpu_lock lock;
+ int counts[CPU_SETSIZE];
+ int reps;
+};
+
+void *test_percpu_spinlock_thread(void *arg)
+{
+ struct spinlock_test_data *data = arg;
+
+ int i, cpu;
+ rseq_configure_cpu_pointer();
+ for (i = 0; i < data->reps; i++) {
+ cpu = rseq_percpu_lock(&data->lock);
+ data->counts[cpu]++;
+ rseq_percpu_unlock(&data->lock, cpu);
+ }
+
+ return 0;
+}
+
+/*
+ * A simple test which implements a sharded counter using a per-cpu lock.
+ * Obviously real applications might prefer to simply use a per-cpu increment;
+ * however, this is reasonable for a test and the lock can be extended to
+ * synchronize more complicated operations.
+ */
+void test_percpu_spinlock()
+{
+ int i, sum;
+ pthread_t test_threads[200];
+ struct spinlock_test_data data;
+
+ memset(&data, 0, sizeof(data));
+ data.reps = 5000;
+
+ for (i = 0; i < 200; i++)
+ pthread_create(&test_threads[i], NULL,
+ test_percpu_spinlock_thread, &data);
+
+ for (i = 0; i < 200; i++)
+ pthread_join(test_threads[i], NULL);
+
+ sum = 0;
+ for (i = 0; i < CPU_SETSIZE; i++)
+ sum += data.counts[i];
+
+ assert(sum == data.reps * 200);
+}
+
+struct percpu_list_node {
+ intptr_t data;
+ struct percpu_list_node *next;
+};
+
+struct percpu_list {
+ struct percpu_list_node *heads[CPU_SETSIZE];
+};
+
+int percpu_list_push(struct percpu_list *list, struct percpu_list_node *node)
+{
+ int cpu;
+
+ do {
+ cpu = rseq_current_cpu();
+ node->next = list->heads[cpu];
+ } while (cpu != rseq_percpu_cmpxchg(cpu,
+ (intptr_t *)&list->heads[cpu], (intptr_t)node->next,
+ (intptr_t)node));
+
+ return cpu;
+}
+
+struct percpu_list_node *percpu_list_pop(struct percpu_list *list)
+{
+ int cpu;
+ struct percpu_list_node *head, *next;
+
+ do {
+ cpu = rseq_current_cpu();
+ head = list->heads[cpu];
+ /*
+ * Unlike a traditional lock-less linked list; the availability
+ * of a cmpxchg-check primitive allows us to implement pop
+ * without concerns over ABA-type races.
+ */
+ if (!head) return 0;
+ next = head->next;
+ } while (cpu != rseq_percpu_cmpxchgcheck(cpu,
+ (intptr_t *)&list->heads[cpu], (intptr_t)head, (intptr_t)next,
+ (intptr_t *)&head->next, (intptr_t)next));
+
+ return head;
+}
+
+
+void *test_percpu_list_thread(void *arg)
+{
+ int i;
+ struct percpu_list *list = (struct percpu_list *)arg;
+
+ rseq_configure_cpu_pointer();
+ for (i = 0; i < 100000; i++) {
+ struct percpu_list_node *node = percpu_list_pop(list);
+ sched_yield(); /* encourage shuffling */
+ if (node) percpu_list_push(list, node);
+ }
+
+ return 0;
+}
+
+/*
+ * Implements a per-cpu linked list then shuffles it via popping and pushing
+ * from many threads.
+ */
+void test_percpu_list()
+{
+ int i, j;
+ long sum = 0, expected_sum = 0;
+ struct percpu_list list;
+ pthread_t test_threads[200];
+ cpu_set_t allowed_cpus;
+
+ memset(&list, 0, sizeof(list));
+
+ /* Generate list entries for every usable cpu. */
+ sched_getaffinity(0, sizeof(allowed_cpus), &allowed_cpus);
+ for (i = 0; i < CPU_SETSIZE; i++) {
+ if (!CPU_ISSET(i, &allowed_cpus)) continue;
+ for (j = 1; j <= 100; j++) {
+ struct percpu_list_node *node;
+
+ expected_sum += j;
+
+ node = malloc(sizeof(*node));
+ assert(node);
+ node->data = j;
+ node->next = list.heads[i];
+ list.heads[i] = node;
+ }
+ }
+
+ for (i = 0; i < 200; i++)
+ assert(pthread_create(&test_threads[i], NULL,
+ test_percpu_list_thread, &list) == 0);
+
+ for (i = 0; i < 200; i++)
+ pthread_join(test_threads[i], NULL);
+
+ for (i = 0; i < CPU_SETSIZE; i++) {
+ cpu_set_t pin_mask;
+ struct percpu_list_node *node;
+
+ if (!CPU_ISSET(i, &allowed_cpus)) continue;
+
+ CPU_ZERO(&pin_mask);
+ CPU_SET(i, &pin_mask);
+ sched_setaffinity(0, sizeof(pin_mask), &pin_mask);
+
+ while ((node = percpu_list_pop(&list))) {
+ sum += node->data;
+ free(node);
+ }
+ }
+
+ /*
+ * All entries should now be accounted for (unless some external actor
+ * is interfering with our allowed affinity while this test is
+ * running).
+ */
+ assert(sum == expected_sum);
+}
+
+/* defined by basic_percpu_ops_test.S */
+extern void *RSEQ_CRITICAL_SECTION_START;
+extern void *RSEQ_CRITICAL_SECTION_END;
+extern void *RSEQ_RESTART_HANDLER;
+
+int main(int argc, char **argv)
+{
+ rseq_configure_region(&RSEQ_CRITICAL_SECTION_START,
+ &RSEQ_CRITICAL_SECTION_END,
+ &RSEQ_RESTART_HANDLER);
+ rseq_configure_cpu_pointer();
+
+ test_percpu_spinlock();
+ test_percpu_list();
+
+ return 0;
+}
+
+#else
+int main(int argc, char **argv)
+{
+ fprintf(stderr, "architecture not supported\n");
+ return 0;
+}
+#endif
diff --git a/tools/testing/selftests/rseq/basic_test.c b/tools/testing/selftests/rseq/basic_test.c
new file mode 100644
index 0000000..cca8edb
--- /dev/null
+++ b/tools/testing/selftests/rseq/basic_test.c
@@ -0,0 +1,76 @@
+/*
+ * Basic test coverage for critical regions and rseq_current_cpu().
+ */
+
+#define _GNU_SOURCE
+#include <assert.h>
+#include <sched.h>
+
+#include "rseq.h"
+
+#define _STRINGIFY(x) #x
+#define STRINGIFY(x) _STRINGIFY(x)
+
+extern void *RSEQ_CRITICAL_SECTION_START;
+extern void *RSEQ_CRITICAL_SECTION_END;
+extern void *RSEQ_RESTART_HANDLER;
+
+/*
+ * Asserts simply that we eventually see *some* event which interrupts our
+ * critical section (which otherwise loops infinitely). This could be
+ * preemption or signal delivery.
+ */
+int test_critical_section()
+{
+ void* restart_address = 0;
+#if defined(__i386__) || defined(__x86_64__)
+ __asm__(
+ ".globl RSEQ_CRITICAL_SECTION_START\n"
+ "RSEQ_CRITICAL_SECTION_START:\n"
+ " jmp RSEQ_CRITICAL_SECTION_START\n" /* while(1) */
+ ".globl RSEQ_CRITICAL_SECTION_END\n"
+ "RSEQ_CRITICAL_SECTION_END:\n"
+ ".globl RSEQ_RESTART_HANDLER\n"
+ "RSEQ_RESTART_HANDLER:\n"
+ " movq %%" STRINGIFY(RESTART_ADDR_REG) ", %0\n"
+ : "=a"(restart_address) ::);
+ assert(restart_address == &RSEQ_CRITICAL_SECTION_START);
+#else
+ fprintf(stderr, "architecture not supported\n");
+#endif
+ return 0;
+}
+
+void test_cpu_pointer()
+{
+ cpu_set_t affinity, test_affinity;
+ int i;
+
+ sched_getaffinity(0, sizeof(affinity), &affinity);
+ CPU_ZERO(&test_affinity);
+ for (i = 0; i < CPU_SETSIZE; i++) {
+ if (CPU_ISSET(i, &affinity)) {
+ CPU_SET(i, &test_affinity);
+ sched_setaffinity(0, sizeof(test_affinity),
+ &test_affinity);
+ assert(rseq_current_cpu() == sched_getcpu());
+ assert(rseq_current_cpu() == i);
+ CPU_CLR(i, &test_affinity);
+ }
+ }
+ sched_setaffinity(0, sizeof(affinity), &affinity);
+}
+
+int main(int argc, char **argv)
+{
+ rseq_configure_region(&RSEQ_CRITICAL_SECTION_START,
+ &RSEQ_CRITICAL_SECTION_END,
+ &RSEQ_RESTART_HANDLER);
+ rseq_configure_cpu_pointer();
+
+ test_critical_section();
+ test_cpu_pointer();
+
+ return 0;
+}
+
diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
new file mode 100644
index 0000000..c1ea5d8
--- /dev/null
+++ b/tools/testing/selftests/rseq/rseq.c
@@ -0,0 +1,48 @@
+#define _GNU_SOURCE
+#include <assert.h>
+#include <errno.h>
+#include <sched.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "rseq.h"
+
+__thread volatile const int __rseq_current_cpu = -1;
+
+#define __NR_rseq 323
+#define SYS_RSEQ_SET_CRITICAL 0
+#define SYS_RSEQ_SET_CPU_POINTER 1
+
+int sys_rseq(int op, int flags, void* val1, void* val2, void* val3)
+{
+ return syscall(__NR_rseq, op, flags,
+ (intptr_t)val1, (intptr_t)val2, (intptr_t)val3);
+}
+
+static void sys_rseq_checked(int op, int flags,
+ void* val1, void* val2, void* val3)
+{
+ int rc = sys_rseq(op, flags, val1, val2, val3);
+ if (rc) {
+ fprintf(stderr,"sys_rseq(%d, %d, %p, %p, %p) failed(%d): %s\n",
+ op, flags, val1, val2, val3, errno, strerror(errno));
+ exit(1);
+ }
+}
+
+void rseq_configure_region(void *rseq_text_start, void *rseq_text_end,
+ void *rseq_restart_handler)
+{
+ sys_rseq_checked(SYS_RSEQ_SET_CRITICAL, 0,
+ rseq_text_start, rseq_text_end, rseq_restart_handler);
+}
+
+void rseq_configure_cpu_pointer(void)
+{
+ sys_rseq_checked(SYS_RSEQ_SET_CPU_POINTER, 0,
+ (void*)&__rseq_current_cpu, 0, 0);
+ assert(rseq_current_cpu() != -1); /* always updated prior to return. */
+}
+
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
new file mode 100644
index 0000000..91bb655
--- /dev/null
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -0,0 +1,28 @@
+#ifndef RSEQ_TEST_H
+#define RSEQ_TEST_H
+
+#if defined(__i386__)
+#define RESTART_ADDR_REG ecx
+#elif defined(__x86_64__)
+#define RESTART_ADDR_REG r10
+#else
+#define RESTART_ADDR_REG unknown
+#endif
+
+#ifndef __ASSEMBLER__
+int sys_rseq(int op, int flags, void* val1, void* val2, void* val3);
+/* RSEQ provided thread-local current_cpu */
+
+void rseq_configure_cpu_pointer(void);
+
+void rseq_configure_region(void *rseq_text_start, void *rseq_text_end,
+ void *rseq_restart_handler);
+
+
+extern __thread volatile const int __rseq_current_cpu;
+static inline int rseq_current_cpu(void) { return __rseq_current_cpu; }
+
+void run_tests();
+#endif
+
+#endif
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