From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 24 Oct 2018 11:54:25 +0000 (-0400)
Subject: Use __rseq_refcount symbol
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=1f7e39d3e152683e8a4afd3174263b4ad3f7a0c6;p=librseq.git

Use __rseq_refcount symbol

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/include/rseq/rseq.h b/include/rseq/rseq.h
index dd1199a..c45cd38 100644
--- a/include/rseq/rseq.h
+++ b/include/rseq/rseq.h
@@ -45,6 +45,7 @@
 #endif
 
 extern __thread volatile struct rseq __rseq_abi;
+extern __thread volatile uint32_t __rseq_refcount;
 
 #define rseq_likely(x)		__builtin_expect(!!(x), 1)
 #define rseq_unlikely(x)	__builtin_expect(!!(x), 0)
diff --git a/src/rseq.c b/src/rseq.c
index 172f4d9..a48f0e0 100644
--- a/src/rseq.c
+++ b/src/rseq.c
@@ -31,29 +31,13 @@
 
 #define ARRAY_SIZE(arr)	(sizeof(arr) / sizeof((arr)[0]))
 
-/*
- * linux/rseq.h defines struct rseq as aligned on 32 bytes. The kernel ABI
- * size is 20 bytes. For support of multiple rseq users within a process,
- * user-space defines an extra 4 bytes field as a reference count, for a
- * total of 24 bytes.
- */
-struct libc_rseq {
-	/* kernel-userspace ABI. */
-	__u32 cpu_id_start;
-	__u32 cpu_id;
-	__u64 rseq_cs;
-	__u32 flags;
-	/* user-space ABI. */
-	__u32 refcount;
-} __attribute__((aligned(4 * sizeof(__u64))));
-
-__attribute__((visibility("hidden"))) __thread
-volatile struct libc_rseq __lib_rseq_abi = {
+__attribute__((weak)) __thread
+volatile struct rseq __rseq_abi = {
 	.cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
 };
 
-extern __attribute__((weak, alias("__lib_rseq_abi"))) __thread
-volatile struct rseq __rseq_abi;
+__attribute__((weak)) __thread
+volatile uint32_t __rseq_refcount;
 
 static int sys_rseq(volatile struct rseq *rseq_abi, uint32_t rseq_len,
 		    int flags, uint32_t sig)
@@ -104,11 +88,11 @@ int rseq_register_current_thread(void)
 	sigset_t oldset;
 
 	signal_off_save(&oldset);
-	if (__lib_rseq_abi.refcount == INT_MAX) {
+	if (__rseq_refcount == UINT_MAX) {
 		ret = -1;
 		goto end;
 	}
-	if (__lib_rseq_abi.refcount++)
+	if (__rseq_refcount++)
 		goto end;
 	rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), 0, RSEQ_SIG);
 	if (!rc) {
@@ -118,7 +102,7 @@ int rseq_register_current_thread(void)
 	if (errno != EBUSY)
 		__rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
 	ret = -1;
-	__lib_rseq_abi.refcount--;
+	__rseq_refcount--;
 end:
 	signal_restore(oldset);
 	return ret;
@@ -130,11 +114,11 @@ int rseq_unregister_current_thread(void)
 	sigset_t oldset;
 
 	signal_off_save(&oldset);
-	if (!__lib_rseq_abi.refcount) {
+	if (!__rseq_refcount) {
 		ret = -1;
 		goto end;
 	}
-	if (--__lib_rseq_abi.refcount)
+	if (--__rseq_refcount)
 		goto end;
 	rc = sys_rseq(&__rseq_abi, sizeof(struct rseq),
 		      RSEQ_FLAG_UNREGISTER, RSEQ_SIG);