Add support to optionally emit different instrumentation for accesses to
volatile variables. While the default TSAN runtime likely will never
require this feature, other runtimes for different environments that
have subtly different memory models or assumptions may require
distinguishing volatiles.
One such environment are OS kernels, where volatile is still used in
various places, and often declare volatile to be appropriate even in
multi-threaded contexts. One such example is the Linux kernel, which
implements various synchronization primitives using volatile
(READ_ONCE(), WRITE_ONCE()).
Here the Kernel Concurrency Sanitizer (KCSAN), is a runtime that uses
TSAN instrumentation but otherwise implements a very different approach
to race detection from TSAN:
https://github.com/google/ktsan/wiki/KCSAN
Due to recent changes in requirements by the Linux kernel, KCSAN
requires that the compiler supports tsan-distinguish-volatile (among
several new requirements):
https://lore.kernel.org/lkml/20200521142047.169334-7-el...@google.com/
gcc/
* params.opt: Define --param=tsan-distinguish-volatile=[0,1].
* sanitizer.def (BUILT_IN_TSAN_VOLATILE_READ1): Define new
builtin for volatile instrumentation of reads/writes.
(BUILT_IN_TSAN_VOLATILE_READ2): Likewise.
(BUILT_IN_TSAN_VOLATILE_READ4): Likewise.
(BUILT_IN_TSAN_VOLATILE_READ8): Likewise.
(BUILT_IN_TSAN_VOLATILE_READ16): Likewise.
(BUILT_IN_TSAN_VOLATILE_WRITE1): Likewise.
(BUILT_IN_TSAN_VOLATILE_WRITE2): Likewise.
(BUILT_IN_TSAN_VOLATILE_WRITE4): Likewise.
(BUILT_IN_TSAN_VOLATILE_WRITE8): Likewise.
(BUILT_IN_TSAN_VOLATILE_WRITE16): Likewise.
* tsan.c (get_memory_access_decl): Argument if access is
volatile. If param tsan-distinguish-volatile is non-zero, and
access if volatile, return volatile instrumentation decl.
(instrument_expr): Check if access is volatile.
gcc/testsuite/
* c-c++-common/tsan/volatile.c: New test.
Acked-by: Dmitry Vyukov <dvyu...@google.com>
---
v3:
* Remove Optimization from -param=tsan-distinguish-volatile.
* Simplify get_memory_access_decl.
* Avoid use of builtin_decl temporary.
v2:
* Add Optimization keyword to -param=tsan-distinguish-volatile= as the
parameter can be different per TU.
* Add tree-dump check to test.
---
gcc/params.opt | 4 ++
gcc/sanitizer.def | 21 +++++++
gcc/testsuite/c-c++-common/tsan/volatile.c | 67 ++++++++++++++++++++++
gcc/tsan.c | 31 +++++-----
4 files changed, 110 insertions(+), 13 deletions(-)
create mode 100644 gcc/testsuite/c-c++-common/tsan/volatile.c
diff --git a/gcc/params.opt b/gcc/params.opt
index 4aec480798b..9b564bb046c 100644
--- a/gcc/params.opt
+++ b/gcc/params.opt
@@ -908,6 +908,10 @@ Stop reverse growth if the reverse probability of best
edge is less than this th
Common Joined UInteger Var(param_tree_reassoc_width) Param Optimization
Set the maximum number of instructions executed in parallel in reassociated
tree. If 0, use the target dependent heuristic.
+-param=tsan-distinguish-volatile=
+Common Joined UInteger Var(param_tsan_distinguish_volatile) IntegerRange(0, 1)
Param
+Emit special instrumentation for accesses to volatiles.
+
-param=uninit-control-dep-attempts=
Common Joined UInteger Var(param_uninit_control_dep_attempts) Init(1000)
IntegerRange(1, 65536) Param Optimization
Maximum number of nested calls to search for control dependencies during
uninitialized variable analysis.
diff --git a/gcc/sanitizer.def b/gcc/sanitizer.def
index 11eb6467eba..a32715ddb92 100644
--- a/gcc/sanitizer.def
+++ b/gcc/sanitizer.def
@@ -214,6 +214,27 @@ DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_READ_RANGE,
"__tsan_read_range",
DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_WRITE_RANGE, "__tsan_write_range",
BT_FN_VOID_PTR_PTRMODE, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_VOLATILE_READ1, "__tsan_volatile_read1",
+ BT_FN_VOID_PTR, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_VOLATILE_READ2, "__tsan_volatile_read2",
+ BT_FN_VOID_PTR, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_VOLATILE_READ4, "__tsan_volatile_read4",
+ BT_FN_VOID_PTR, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_VOLATILE_READ8, "__tsan_volatile_read8",
+ BT_FN_VOID_PTR, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_VOLATILE_READ16, "__tsan_volatile_read16",
+ BT_FN_VOID_PTR, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_VOLATILE_WRITE1, "__tsan_volatile_write1",
+ BT_FN_VOID_PTR, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_VOLATILE_WRITE2, "__tsan_volatile_write2",
+ BT_FN_VOID_PTR, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_VOLATILE_WRITE4, "__tsan_volatile_write4",
+ BT_FN_VOID_PTR, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_VOLATILE_WRITE8, "__tsan_volatile_write8",
+ BT_FN_VOID_PTR, ATTR_NOTHROW_LEAF_LIST)
+DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_VOLATILE_WRITE16,
"__tsan_volatile_write16",
+ BT_FN_VOID_PTR, ATTR_NOTHROW_LEAF_LIST)
+
DEF_SANITIZER_BUILTIN(BUILT_IN_TSAN_ATOMIC8_LOAD,
"__tsan_atomic8_load",
BT_FN_I1_CONST_VPTR_INT, ATTR_NOTHROW_LEAF_LIST)
diff --git a/gcc/testsuite/c-c++-common/tsan/volatile.c
b/gcc/testsuite/c-c++-common/tsan/volatile.c
new file mode 100644
index 00000000000..68379921685
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/tsan/volatile.c
@@ -0,0 +1,67 @@
+/* { dg-options "--param=tsan-distinguish-volatile=1 -fdump-tree-optimized" }
*/
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdio.h>
+
+int32_t Global4;
+volatile int32_t VolatileGlobal4;
+volatile int64_t VolatileGlobal8;
+
+static int nvolatile_reads;
+static int nvolatile_writes;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+__attribute__((no_sanitize_thread))
+void __tsan_volatile_read4(void *addr) {
+ assert(addr == &VolatileGlobal4);
+ nvolatile_reads++;
+}
+__attribute__((no_sanitize_thread))
+void __tsan_volatile_write4(void *addr) {
+ assert(addr == &VolatileGlobal4);
+ nvolatile_writes++;
+}
+__attribute__((no_sanitize_thread))
+void __tsan_volatile_read8(void *addr) {
+ assert(addr == &VolatileGlobal8);
+ nvolatile_reads++;
+}
+__attribute__((no_sanitize_thread))
+void __tsan_volatile_write8(void *addr) {
+ assert(addr == &VolatileGlobal8);
+ nvolatile_writes++;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+__attribute__((no_sanitize_thread))
+static void check() {
+ assert(nvolatile_reads == 4);
+ assert(nvolatile_writes == 4);
+}
+
+int main() {
+ Global4 = 1;
+
+ VolatileGlobal4 = 1;
+ Global4 = VolatileGlobal4;
+ VolatileGlobal4 = 1 + VolatileGlobal4;
+
+ VolatileGlobal8 = 1;
+ Global4 = (int32_t)VolatileGlobal8;
+ VolatileGlobal8 = 1 + VolatileGlobal8;
+
+ check();
+ return 0;
+}
+
+// { dg-final { scan-tree-dump-times "__tsan_volatile_read4
\\(&VolatileGlobal4" 2 "optimized" } }
+// { dg-final { scan-tree-dump-times "__tsan_volatile_read8
\\(&VolatileGlobal8" 2 "optimized" } }
+// { dg-final { scan-tree-dump-times "__tsan_volatile_write4
\\(&VolatileGlobal4" 2 "optimized" } }
+// { dg-final { scan-tree-dump-times "__tsan_volatile_write8
\\(&VolatileGlobal8" 2 "optimized" } }
diff --git a/gcc/tsan.c b/gcc/tsan.c
index 8d22a776377..fcb2653ebbe 100644
--- a/gcc/tsan.c
+++ b/gcc/tsan.c
@@ -52,25 +52,29 @@ along with GCC; see the file COPYING3. If not see
void __tsan_read/writeX (void *addr); */
static tree
-get_memory_access_decl (bool is_write, unsigned size)
+get_memory_access_decl (bool is_write, unsigned size, bool volatilep)
{
enum built_in_function fcode;
+ int pos;
if (size <= 1)
- fcode = is_write ? BUILT_IN_TSAN_WRITE1
- : BUILT_IN_TSAN_READ1;
+ pos = 0;
else if (size <= 3)
- fcode = is_write ? BUILT_IN_TSAN_WRITE2
- : BUILT_IN_TSAN_READ2;
+ pos = 1;
else if (size <= 7)
- fcode = is_write ? BUILT_IN_TSAN_WRITE4
- : BUILT_IN_TSAN_READ4;
+ pos = 2;
else if (size <= 15)
- fcode = is_write ? BUILT_IN_TSAN_WRITE8
- : BUILT_IN_TSAN_READ8;
+ pos = 3;
+ else
+ pos = 4;
+
+ if (param_tsan_distinguish_volatile && volatilep)
+ fcode = is_write ? BUILT_IN_TSAN_VOLATILE_WRITE1
+ : BUILT_IN_TSAN_VOLATILE_READ1;
else
- fcode = is_write ? BUILT_IN_TSAN_WRITE16
- : BUILT_IN_TSAN_READ16;
+ fcode = is_write ? BUILT_IN_TSAN_WRITE1
+ : BUILT_IN_TSAN_READ1;
+ fcode = (built_in_function)(fcode + pos);
return builtin_decl_implicit (fcode);
}
@@ -204,8 +208,9 @@ instrument_expr (gimple_stmt_iterator gsi, tree expr, bool
is_write)
g = gimple_build_call (builtin_decl, 2, expr_ptr, size_int (size));
}
else if (rhs == NULL)
- g = gimple_build_call (get_memory_access_decl (is_write, size),
- 1, expr_ptr);
+ g = gimple_build_call (get_memory_access_decl (is_write, size,
+ TREE_THIS_VOLATILE (expr)),
+ 1, expr_ptr);
else
{
builtin_decl = builtin_decl_implicit (BUILT_IN_TSAN_VPTR_UPDATE);
--
2.27.0.278.ge193c7cf3a9-goog
