[GWP-ASan] Abstract the thread local variables access
In a similar fashion to D87420 for Scudo, this CL introduces a way to
get thread local variables via a platform-specific reserved TLS slot,
since Fuchsia doesn't support ELF TLS from the libc itself.
If needing to use this, a platform will have to define
`GWP_ASAN_HAS_PLATFORM_TLS_SLOT` and provide `gwp_asan_platform_tls_slot.h`
which will define a `uint64_t *getPlatformGwpAsanTlsSlot()` function
that will return the TLS word of storage.
I snuck in a couple of cleanup items as well, moving some static
functions to anonymous namespace for consistency.
Differential Revision: https://reviews.llvm.org/D90195
GitOrigin-RevId: 90678f65ae47523586bd34392ed3cd1369cf5e9b
diff --git a/guarded_pool_allocator.cpp b/guarded_pool_allocator.cpp
index 6c4f2b8..a895032 100644
--- a/guarded_pool_allocator.cpp
+++ b/guarded_pool_allocator.cpp
@@ -37,6 +37,14 @@
// referenced by users outside this translation unit, in order to avoid
// init-order-fiasco.
GuardedPoolAllocator *SingletonPtr = nullptr;
+
+size_t roundUpTo(size_t Size, size_t Boundary) {
+ return (Size + Boundary - 1) & ~(Boundary - 1);
+}
+
+uintptr_t getPageAddr(uintptr_t Ptr, uintptr_t PageSize) {
+ return Ptr & ~(PageSize - 1);
+}
} // anonymous namespace
// Gets the singleton implementation of this class. Thread-compatible until
@@ -45,10 +53,6 @@
return SingletonPtr;
}
-static size_t roundUpTo(size_t Size, size_t Boundary) {
- return (Size + Boundary - 1) & ~(Boundary - 1);
-}
-
void GuardedPoolAllocator::init(const options::Options &Opts) {
// Note: We return from the constructor here if GWP-ASan is not available.
// This will stop heap-allocation of class members, as well as mmap() of the
@@ -99,7 +103,7 @@
AdjustedSampleRatePlusOne = 2;
initPRNG();
- ThreadLocals.NextSampleCounter =
+ getThreadLocals()->NextSampleCounter =
((getRandomUnsigned32() % (AdjustedSampleRatePlusOne - 1)) + 1) &
ThreadLocalPackedVariables::NextSampleCounterMask;
@@ -146,22 +150,18 @@
}
}
-static uintptr_t getPageAddr(uintptr_t Ptr, uintptr_t PageSize) {
- return Ptr & ~(PageSize - 1);
-}
-
void *GuardedPoolAllocator::allocate(size_t Size) {
// GuardedPagePoolEnd == 0 when GWP-ASan is disabled. If we are disabled, fall
// back to the supporting allocator.
if (State.GuardedPagePoolEnd == 0) {
- ThreadLocals.NextSampleCounter =
+ getThreadLocals()->NextSampleCounter =
(AdjustedSampleRatePlusOne - 1) &
ThreadLocalPackedVariables::NextSampleCounterMask;
return nullptr;
}
// Protect against recursivity.
- if (ThreadLocals.RecursiveGuard)
+ if (getThreadLocals()->RecursiveGuard)
return nullptr;
ScopedRecursiveGuard SRG;
@@ -212,7 +212,7 @@
}
void GuardedPoolAllocator::stop() {
- ThreadLocals.RecursiveGuard = true;
+ getThreadLocals()->RecursiveGuard = true;
PoolMutex.tryLock();
}
@@ -243,7 +243,7 @@
// Ensure that the unwinder is not called if the recursive flag is set,
// otherwise non-reentrant unwinders may deadlock.
- if (!ThreadLocals.RecursiveGuard) {
+ if (!getThreadLocals()->RecursiveGuard) {
ScopedRecursiveGuard SRG;
Meta->DeallocationTrace.RecordBacktrace(Backtrace);
}
@@ -290,15 +290,11 @@
}
uint32_t GuardedPoolAllocator::getRandomUnsigned32() {
- uint32_t RandomState = ThreadLocals.RandomState;
+ uint32_t RandomState = getThreadLocals()->RandomState;
RandomState ^= RandomState << 13;
RandomState ^= RandomState >> 17;
RandomState ^= RandomState << 5;
- ThreadLocals.RandomState = RandomState;
+ getThreadLocals()->RandomState = RandomState;
return RandomState;
}
-
-GWP_ASAN_TLS_INITIAL_EXEC
-GuardedPoolAllocator::ThreadLocalPackedVariables
- GuardedPoolAllocator::ThreadLocals;
} // namespace gwp_asan
diff --git a/guarded_pool_allocator.h b/guarded_pool_allocator.h
index 294a5b4..5ce70e4 100644
--- a/guarded_pool_allocator.h
+++ b/guarded_pool_allocator.h
@@ -13,6 +13,7 @@
#include "gwp_asan/definitions.h"
#include "gwp_asan/mutex.h"
#include "gwp_asan/options.h"
+#include "gwp_asan/platform_specific/guarded_pool_allocator_tls.h"
#include "gwp_asan/stack_trace_compressor.h"
#include <stddef.h>
@@ -77,12 +78,12 @@
// class must be valid when zero-initialised, and we wish to sample as
// infrequently as possible when this is the case, hence we underflow to
// UINT32_MAX.
- if (GWP_ASAN_UNLIKELY(ThreadLocals.NextSampleCounter == 0))
- ThreadLocals.NextSampleCounter =
+ if (GWP_ASAN_UNLIKELY(getThreadLocals()->NextSampleCounter == 0))
+ getThreadLocals()->NextSampleCounter =
((getRandomUnsigned32() % (AdjustedSampleRatePlusOne - 1)) + 1) &
ThreadLocalPackedVariables::NextSampleCounterMask;
- return GWP_ASAN_UNLIKELY(--ThreadLocals.NextSampleCounter == 0);
+ return GWP_ASAN_UNLIKELY(--getThreadLocals()->NextSampleCounter == 0);
}
// Returns whether the provided pointer is a current sampled allocation that
@@ -206,37 +207,10 @@
// the sample rate.
uint32_t AdjustedSampleRatePlusOne = 0;
- // Pack the thread local variables into a struct to ensure that they're in
- // the same cache line for performance reasons. These are the most touched
- // variables in GWP-ASan.
- struct alignas(8) ThreadLocalPackedVariables {
- constexpr ThreadLocalPackedVariables()
- : RandomState(0xff82eb50), NextSampleCounter(0), RecursiveGuard(false) {
- }
- // Initialised to a magic constant so that an uninitialised GWP-ASan won't
- // regenerate its sample counter for as long as possible. The xorshift32()
- // algorithm used below results in getRandomUnsigned32(0xff82eb50) ==
- // 0xfffffea4.
- uint32_t RandomState;
- // Thread-local decrementing counter that indicates that a given allocation
- // should be sampled when it reaches zero.
- uint32_t NextSampleCounter : 31;
- // The mask is needed to silence conversion errors.
- static const uint32_t NextSampleCounterMask = (1U << 31) - 1;
- // Guard against recursivity. Unwinders often contain complex behaviour that
- // may not be safe for the allocator (i.e. the unwinder calls dlopen(),
- // which calls malloc()). When recursive behaviour is detected, we will
- // automatically fall back to the supporting allocator to supply the
- // allocation.
- bool RecursiveGuard : 1;
- };
- static_assert(sizeof(ThreadLocalPackedVariables) == sizeof(uint64_t),
- "thread local data does not fit in a uint64_t");
-
class ScopedRecursiveGuard {
public:
- ScopedRecursiveGuard() { ThreadLocals.RecursiveGuard = true; }
- ~ScopedRecursiveGuard() { ThreadLocals.RecursiveGuard = false; }
+ ScopedRecursiveGuard() { getThreadLocals()->RecursiveGuard = true; }
+ ~ScopedRecursiveGuard() { getThreadLocals()->RecursiveGuard = false; }
};
// Initialise the PRNG, platform-specific.
@@ -245,8 +219,6 @@
// xorshift (32-bit output), extremely fast PRNG that uses arithmetic
// operations only. Seeded using platform-specific mechanisms by initPRNG().
uint32_t getRandomUnsigned32();
-
- static GWP_ASAN_TLS_INITIAL_EXEC ThreadLocalPackedVariables ThreadLocals;
};
} // namespace gwp_asan
diff --git a/platform_specific/guarded_pool_allocator_posix.cpp b/platform_specific/guarded_pool_allocator_posix.cpp
index 21b622c..dad749b 100644
--- a/platform_specific/guarded_pool_allocator_posix.cpp
+++ b/platform_specific/guarded_pool_allocator_posix.cpp
@@ -38,7 +38,7 @@
namespace gwp_asan {
void GuardedPoolAllocator::initPRNG() {
- ThreadLocals.RandomState =
+ getThreadLocals()->RandomState =
static_cast<uint32_t>(time(nullptr) + getThreadID());
}
diff --git a/platform_specific/guarded_pool_allocator_tls.h b/platform_specific/guarded_pool_allocator_tls.h
new file mode 100644
index 0000000..28b37e7
--- /dev/null
+++ b/platform_specific/guarded_pool_allocator_tls.h
@@ -0,0 +1,53 @@
+//===-- guarded_pool_allocator_tls.h ----------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef GWP_ASAN_GUARDED_POOL_ALLOCATOR_TLS_H_
+#define GWP_ASAN_GUARDED_POOL_ALLOCATOR_TLS_H_
+
+#include "gwp_asan/definitions.h"
+
+#include <stdint.h>
+
+namespace gwp_asan {
+// Pack the thread local variables into a struct to ensure that they're in
+// the same cache line for performance reasons. These are the most touched
+// variables in GWP-ASan.
+struct ThreadLocalPackedVariables {
+ constexpr ThreadLocalPackedVariables()
+ : RandomState(0xacd979ce), NextSampleCounter(0), RecursiveGuard(false) {}
+ // Initialised to a magic constant so that an uninitialised GWP-ASan won't
+ // regenerate its sample counter for as long as possible. The xorshift32()
+ // algorithm used below results in getRandomUnsigned32(0xacd979ce) ==
+ // 0xfffffffe.
+ uint32_t RandomState;
+ // Thread-local decrementing counter that indicates that a given allocation
+ // should be sampled when it reaches zero.
+ uint32_t NextSampleCounter : 31;
+ // The mask is needed to silence conversion errors.
+ static const uint32_t NextSampleCounterMask = (1U << 31) - 1;
+ // Guard against recursivity. Unwinders often contain complex behaviour that
+ // may not be safe for the allocator (i.e. the unwinder calls dlopen(),
+ // which calls malloc()). When recursive behaviour is detected, we will
+ // automatically fall back to the supporting allocator to supply the
+ // allocation.
+ bool RecursiveGuard : 1;
+};
+static_assert(sizeof(ThreadLocalPackedVariables) == sizeof(uint64_t),
+ "thread local data does not fit in a uint64_t");
+
+#ifdef GWP_ASAN_PLATFORM_TLS_HEADER
+#include GWP_ASAN_PLATFORM_TLS_HEADER
+#else
+inline ThreadLocalPackedVariables *getThreadLocals() {
+ alignas(8) static GWP_ASAN_TLS_INITIAL_EXEC ThreadLocalPackedVariables Locals;
+ return &Locals;
+}
+#endif
+} // namespace gwp_asan
+
+#endif // GWP_ASAN_GUARDED_POOL_ALLOCATOR_TLS_H_
diff --git a/platform_specific/utilities_posix.cpp b/platform_specific/utilities_posix.cpp
index 477a7ff..7ee7659 100644
--- a/platform_specific/utilities_posix.cpp
+++ b/platform_specific/utilities_posix.cpp
@@ -24,7 +24,7 @@
if (&android_set_abort_message != nullptr)
android_set_abort_message(Message);
abort();
-#else // __BIONIC__
+#else // __BIONIC__
fprintf(stderr, "%s", Message);
__builtin_trap();
#endif // __BIONIC__
diff --git a/utilities.cpp b/utilities.cpp
index 902e145..287630f 100644
--- a/utilities.cpp
+++ b/utilities.cpp
@@ -37,7 +37,7 @@
#ifdef __BIONIC__
static constexpr AlignmentStrategy PlatformDefaultAlignment =
AlignmentStrategy::BIONIC;
-#else // __BIONIC__
+#else // __BIONIC__
static constexpr AlignmentStrategy PlatformDefaultAlignment =
AlignmentStrategy::POWER_OF_TWO;
#endif // __BIONIC__
