* [PATCH] tests/tcg/multiarch: add vma-pthread.c
[not found] <20221223115348.tgfwdlektsulebxk@heavy>
@ 2022-12-23 12:02 ` Ilya Leoshkevich
2022-12-23 12:09 ` Ilya Leoshkevich
2022-12-24 15:01 ` Richard Henderson
0 siblings, 2 replies; 3+ messages in thread
From: Ilya Leoshkevich @ 2022-12-23 12:02 UTC (permalink / raw)
To: Richard Henderson; +Cc: qemu-devel, Ilya Leoshkevich
Add a test that locklessly changes and exercises page protection bits
from various threads. This helps catch race conditions in the VMA
handling.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
tests/tcg/multiarch/Makefile.target | 3 +
tests/tcg/multiarch/munmap-pthread.c | 16 +--
tests/tcg/multiarch/nop_func.h | 25 ++++
tests/tcg/multiarch/vma-pthread.c | 185 +++++++++++++++++++++++++++
4 files changed, 214 insertions(+), 15 deletions(-)
create mode 100644 tests/tcg/multiarch/nop_func.h
create mode 100644 tests/tcg/multiarch/vma-pthread.c
diff --git a/tests/tcg/multiarch/Makefile.target b/tests/tcg/multiarch/Makefile.target
index 5f0fee1aadb..e7213af4925 100644
--- a/tests/tcg/multiarch/Makefile.target
+++ b/tests/tcg/multiarch/Makefile.target
@@ -39,6 +39,9 @@ signals: LDFLAGS+=-lrt -lpthread
munmap-pthread: CFLAGS+=-pthread
munmap-pthread: LDFLAGS+=-pthread
+vma-pthread: CFLAGS+=-pthread
+vma-pthread: LDFLAGS+=-pthread
+
# We define the runner for test-mmap after the individual
# architectures have defined their supported pages sizes. If no
# additional page sizes are defined we only run the default test.
diff --git a/tests/tcg/multiarch/munmap-pthread.c b/tests/tcg/multiarch/munmap-pthread.c
index d7143b00d5f..1c79005846d 100644
--- a/tests/tcg/multiarch/munmap-pthread.c
+++ b/tests/tcg/multiarch/munmap-pthread.c
@@ -7,21 +7,7 @@
#include <sys/mman.h>
#include <unistd.h>
-static const char nop_func[] = {
-#if defined(__aarch64__)
- 0xc0, 0x03, 0x5f, 0xd6, /* ret */
-#elif defined(__alpha__)
- 0x01, 0x80, 0xFA, 0x6B, /* ret */
-#elif defined(__arm__)
- 0x1e, 0xff, 0x2f, 0xe1, /* bx lr */
-#elif defined(__riscv)
- 0x67, 0x80, 0x00, 0x00, /* ret */
-#elif defined(__s390__)
- 0x07, 0xfe, /* br %r14 */
-#elif defined(__i386__) || defined(__x86_64__)
- 0xc3, /* ret */
-#endif
-};
+#include "nop_func.h"
static void *thread_mmap_munmap(void *arg)
{
diff --git a/tests/tcg/multiarch/nop_func.h b/tests/tcg/multiarch/nop_func.h
new file mode 100644
index 00000000000..f714d210000
--- /dev/null
+++ b/tests/tcg/multiarch/nop_func.h
@@ -0,0 +1,25 @@
+/*
+ * No-op functions that can be safely copied.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#ifndef NOP_FUNC_H
+#define NOP_FUNC_H
+
+static const char nop_func[] = {
+#if defined(__aarch64__)
+ 0xc0, 0x03, 0x5f, 0xd6, /* ret */
+#elif defined(__alpha__)
+ 0x01, 0x80, 0xFA, 0x6B, /* ret */
+#elif defined(__arm__)
+ 0x1e, 0xff, 0x2f, 0xe1, /* bx lr */
+#elif defined(__riscv)
+ 0x67, 0x80, 0x00, 0x00, /* ret */
+#elif defined(__s390__)
+ 0x07, 0xfe, /* br %r14 */
+#elif defined(__i386__) || defined(__x86_64__)
+ 0xc3, /* ret */
+#endif
+};
+
+#endif
diff --git a/tests/tcg/multiarch/vma-pthread.c b/tests/tcg/multiarch/vma-pthread.c
new file mode 100644
index 00000000000..c405cd46329
--- /dev/null
+++ b/tests/tcg/multiarch/vma-pthread.c
@@ -0,0 +1,185 @@
+/*
+ * Test that VMA updates do not race.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * Map a contiguous chunk of RWX memory. Split it into 8 equally sized
+ * regions, each of which is guaranteed to have a certain combination of
+ * protection bits set.
+ *
+ * Reader, writer and executor threads perform the respective operations on
+ * pages, which are guaranteed to have the respective protection bit set.
+ * Two mutator threads change the non-fixed protection bits randomly.
+ */
+#include <assert.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include "nop_func.h"
+
+#define PAGE_IDX_BITS 10
+#define PAGE_COUNT (1 << PAGE_IDX_BITS)
+#define PAGE_IDX_MASK (PAGE_COUNT - 1)
+#define REGION_IDX_BITS 3
+#define PAGE_IDX_R_MASK (1 << 7)
+#define PAGE_IDX_W_MASK (1 << 8)
+#define PAGE_IDX_X_MASK (1 << 9)
+#define REGION_MASK (PAGE_IDX_R_MASK | PAGE_IDX_W_MASK | PAGE_IDX_X_MASK)
+#define PAGES_PER_REGION (1 << (PAGE_IDX_BITS - REGION_IDX_BITS))
+
+struct context {
+ int pagesize;
+ char *ptr;
+ int dev_null_fd;
+ volatile int mutator_count;
+};
+
+static void *thread_read(void *arg)
+{
+ struct context *ctx = arg;
+ ssize_t sret;
+ size_t i, j;
+ int ret;
+
+ for (i = 0; ctx->mutator_count; i++) {
+ j = (i & PAGE_IDX_MASK) | PAGE_IDX_R_MASK;
+ /* Read directly. */
+ ret = memcmp(&ctx->ptr[j * ctx->pagesize], nop_func, sizeof(nop_func));
+ assert(ret == 0);
+ /* Read indirectly. */
+ sret = write(ctx->dev_null_fd, &ctx->ptr[j * ctx->pagesize], 1);
+ assert(sret == 1);
+ }
+
+ return NULL;
+}
+
+static void *thread_write(void *arg)
+{
+ struct context *ctx = arg;
+ struct timespec *ts;
+ size_t i, j;
+ int ret;
+
+ for (i = 0; ctx->mutator_count; i++) {
+ j = (i & PAGE_IDX_MASK) | PAGE_IDX_W_MASK;
+ /* Write directly. */
+ memcpy(&ctx->ptr[j * ctx->pagesize], nop_func, sizeof(nop_func));
+ /* Write using a syscall. */
+ ts = (struct timespec *)(&ctx->ptr[(j + 1) * ctx->pagesize] -
+ sizeof(struct timespec));
+ ret = clock_gettime(CLOCK_REALTIME, ts);
+ assert(ret == 0);
+ }
+
+ return NULL;
+}
+
+static void *thread_execute(void *arg)
+{
+ struct context *ctx = arg;
+ size_t i, j;
+
+ for (i = 0; ctx->mutator_count; i++) {
+ j = (i & PAGE_IDX_MASK) | PAGE_IDX_X_MASK;
+ ((void(*)(void))&ctx->ptr[j * ctx->pagesize])();
+ }
+
+ return NULL;
+}
+
+static void *thread_mutate(void *arg)
+{
+ size_t i, start_idx, end_idx, page_idx, tmp;
+ struct context *ctx = arg;
+ unsigned int seed;
+ int prot, ret;
+
+ seed = (unsigned int)time(NULL);
+ for (i = 0; i < 50000; i++) {
+ start_idx = rand_r(&seed) & PAGE_IDX_MASK;
+ end_idx = rand_r(&seed) & PAGE_IDX_MASK;
+ if (start_idx > end_idx) {
+ tmp = start_idx;
+ start_idx = end_idx;
+ end_idx = tmp;
+ }
+ prot = rand_r(&seed) & (PROT_READ | PROT_WRITE | PROT_EXEC);
+ for (page_idx = start_idx & REGION_MASK; page_idx <= end_idx;
+ page_idx += PAGES_PER_REGION) {
+ if (page_idx & PAGE_IDX_R_MASK) {
+ prot |= PROT_READ;
+ }
+ if (page_idx & PAGE_IDX_W_MASK) {
+ prot |= PROT_WRITE;
+ }
+ if (page_idx & PAGE_IDX_X_MASK) {
+ prot |= PROT_EXEC;
+ }
+ }
+ ret = mprotect(&ctx->ptr[start_idx * ctx->pagesize],
+ (end_idx - start_idx + 1) * ctx->pagesize, prot);
+ assert(ret == 0);
+ }
+
+ __atomic_fetch_sub(&ctx->mutator_count, 1, __ATOMIC_SEQ_CST);
+
+ return NULL;
+}
+
+int main(void)
+{
+ pthread_t threads[5];
+ struct context ctx;
+ size_t i;
+ int ret;
+
+ /* Without a template, nothing to test. */
+ if (sizeof(nop_func) == 0) {
+ return EXIT_SUCCESS;
+ }
+
+ /* Initialize memory chunk. */
+ ctx.pagesize = getpagesize();
+ ctx.ptr = mmap(NULL, PAGE_COUNT * ctx.pagesize,
+ PROT_READ | PROT_WRITE | PROT_EXEC,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ assert(ctx.ptr != MAP_FAILED);
+ for (i = 0; i < PAGE_COUNT; i++) {
+ memcpy(&ctx.ptr[i * ctx.pagesize], nop_func, sizeof(nop_func));
+ }
+ ctx.dev_null_fd = open("/dev/null", O_WRONLY);
+ assert(ctx.dev_null_fd >= 0);
+ ctx.mutator_count = 2;
+
+ /* Start threads. */
+ ret = pthread_create(&threads[0], NULL, thread_read, &ctx);
+ assert(ret == 0);
+ ret = pthread_create(&threads[1], NULL, thread_write, &ctx);
+ assert(ret == 0);
+ ret = pthread_create(&threads[2], NULL, thread_execute, &ctx);
+ assert(ret == 0);
+ for (i = 3; i <= 4; i++) {
+ ret = pthread_create(&threads[i], NULL, thread_mutate, &ctx);
+ assert(ret == 0);
+ }
+
+ /* Wait for threads to stop. */
+ for (i = 0; i < sizeof(threads) / sizeof(threads[0]); i++) {
+ ret = pthread_join(threads[i], NULL);
+ assert(ret == 0);
+ }
+
+ /* Destroy memory chunk. */
+ ret = close(ctx.dev_null_fd);
+ assert(ret == 0);
+ ret = munmap(ctx.ptr, PAGE_COUNT * ctx.pagesize);
+ assert(ret == 0);
+
+ return EXIT_SUCCESS;
+}
--
2.38.1
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