From ab2789ec507a94f1a75a6534bca51c7b39037ce0 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Tue, 9 Jun 2020 15:15:39 +0200 Subject: [PATCH] tsan: Add optional support for distinguishing volatiles 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-elver@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. --- gcc/params.opt | 4 ++ gcc/sanitizer.def | 21 ++++++++++ gcc/testsuite/c-c++-common/tsan/volatile.c | 67 ++++++++++++++++++++++++++++++ gcc/tsan.c | 29 +++++++------ 4 files changed, 109 insertions(+), 12 deletions(-) create mode 100644 gcc/testsuite/c-c++-common/tsan/volatile.c diff --git a/gcc/params.opt b/gcc/params.opt index 4aec480..9b564bb 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 11eb646..a32715d 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 0000000..6837992 --- /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 +#include +#include + +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 8d22a77..447accc 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); } @@ -204,7 +208,8 @@ 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), + g = gimple_build_call (get_memory_access_decl (is_write, size, + TREE_THIS_VOLATILE (expr)), 1, expr_ptr); else { -- 2.7.4