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2023-12-08 01573e231f18eb2d99162747186f59511f56b64d

 kernel/tools/testing/selftests/rseq/rseq.c
..
..
@@ -25,83 +25,115 @@
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 #include <syscall.h>
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 #include <assert.h>
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 #include <signal.h>
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+#include <limits.h>
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+#include <dlfcn.h>
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+#include <stddef.h>
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31
 
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+#include "../kselftest.h"
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 #include "rseq.h"
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34
 
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-#define ARRAY_SIZE(arr)	(sizeof(arr) / sizeof((arr)[0]))
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+static const ptrdiff_t *libc_rseq_offset_p;
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+static const unsigned int *libc_rseq_size_p;
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+static const unsigned int *libc_rseq_flags_p;
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-__attribute__((tls_model("initial-exec"))) __thread
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-volatile struct rseq __rseq_abi = {
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-	.cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
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+/* Offset from the thread pointer to the rseq area.  */
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+ptrdiff_t rseq_offset;
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+
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+/* Size of the registered rseq area.  0 if the registration was
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+   unsuccessful.  */
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+unsigned int rseq_size = -1U;
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+
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+/* Flags used during rseq registration.  */
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+unsigned int rseq_flags;
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+
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+static int rseq_ownership;
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+
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+static
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+__thread struct rseq_abi __rseq_abi __attribute__((tls_model("initial-exec"))) = {
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+	.cpu_id = RSEQ_ABI_CPU_ID_UNINITIALIZED,
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 };
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-static __attribute__((tls_model("initial-exec"))) __thread
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-volatile int refcount;
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-
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-static void signal_off_save(sigset_t *oldset)
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-{
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-	sigset_t set;
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-	int ret;
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-
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-	sigfillset(&set);
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-	ret = pthread_sigmask(SIG_BLOCK, &set, oldset);
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-	if (ret)
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-		abort();
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-}
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-
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-static void signal_restore(sigset_t oldset)
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-{
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-	int ret;
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-
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-	ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
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-	if (ret)
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-		abort();
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-}
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-
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-static int sys_rseq(volatile struct rseq *rseq_abi, uint32_t rseq_len,
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+static int sys_rseq(struct rseq_abi *rseq_abi, uint32_t rseq_len,
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57
 		    int flags, uint32_t sig)
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 {
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 	return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig);
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60
 }
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61
 
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+int rseq_available(void)
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+{
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+	int rc;
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+
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+	rc = sys_rseq(NULL, 0, 0, 0);
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+	if (rc != -1)
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+		abort();
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+	switch (errno) {
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+	case ENOSYS:
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+		return 0;
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+	case EINVAL:
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+		return 1;
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+	default:
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+		abort();
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+	}
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+}
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+
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 int rseq_register_current_thread(void)
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 {
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-	int rc, ret = 0;
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-	sigset_t oldset;
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+	int rc;
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82
 
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-	signal_off_save(&oldset);
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-	if (refcount++)
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-		goto end;
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-	rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), 0, RSEQ_SIG);
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-	if (!rc) {
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-		assert(rseq_current_cpu_raw() >= 0);
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-		goto end;
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+	if (!rseq_ownership) {
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+		/* Treat libc's ownership as a successful registration. */
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+		return 0;
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 	}
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-	if (errno != EBUSY)
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-		__rseq_abi.cpu_id = -2;
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-	ret = -1;
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-	refcount--;
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-end:
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-	signal_restore(oldset);
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-	return ret;
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+	rc = sys_rseq(&__rseq_abi, sizeof(struct rseq_abi), 0, RSEQ_SIG);
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+	if (rc)
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+		return -1;
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+	assert(rseq_current_cpu_raw() >= 0);
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+	return 0;
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 }
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93
 
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 int rseq_unregister_current_thread(void)
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 {
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-	int rc, ret = 0;
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-	sigset_t oldset;
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+	int rc;
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-	signal_off_save(&oldset);
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-	if (--refcount)
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-		goto end;
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-	rc = sys_rseq(&__rseq_abi, sizeof(struct rseq),
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-		      RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
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-	if (!rc)
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-		goto end;
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-	ret = -1;
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-end:
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-	signal_restore(oldset);
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-	return ret;
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+	if (!rseq_ownership) {
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+		/* Treat libc's ownership as a successful unregistration. */
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+		return 0;
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+	}
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+	rc = sys_rseq(&__rseq_abi, sizeof(struct rseq_abi), RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);
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+	if (rc)
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+		return -1;
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+	return 0;
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+}
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+
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+static __attribute__((constructor))
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+void rseq_init(void)
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+{
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+	libc_rseq_offset_p = dlsym(RTLD_NEXT, "__rseq_offset");
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+	libc_rseq_size_p = dlsym(RTLD_NEXT, "__rseq_size");
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+	libc_rseq_flags_p = dlsym(RTLD_NEXT, "__rseq_flags");
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+	if (libc_rseq_size_p && libc_rseq_offset_p && libc_rseq_flags_p) {
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+		/* rseq registration owned by glibc */
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+		rseq_offset = *libc_rseq_offset_p;
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+		rseq_size = *libc_rseq_size_p;
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+		rseq_flags = *libc_rseq_flags_p;
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+		return;
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+	}
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+	if (!rseq_available())
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+		return;
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+	rseq_ownership = 1;
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+	rseq_offset = (void *)&__rseq_abi - rseq_thread_pointer();
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+	rseq_size = sizeof(struct rseq_abi);
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+	rseq_flags = 0;
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+}
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+
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+static __attribute__((destructor))
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+void rseq_exit(void)
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+{
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+	if (!rseq_ownership)
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+		return;
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+	rseq_offset = 0;
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+	rseq_size = -1U;
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+	rseq_ownership = 0;
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137
 }
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138
 
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 int32_t rseq_fallback_current_cpu(void)