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Bug 1866606 - Remove MozTaggedMemoryIsSupported. r=jld

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MozTaggedMemoryIsSupported doesn't work under ASAN because it tries to prctl the
nullptr page. It should be harmless to simply call prctl and ignore the error.

Depends on D195064

Differential Revision: https://phabricator.services.mozilla.com/D195065
This commit is contained in:
Benjamin Peterson
2023-12-23 03:36:53 +00:00
parent f94d735749
commit ca85c591b9
2 changed files with 15 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
mfbt/TaggedAnonymousMemory.cpp
View File

@@ -53,38 +53,28 @@ static uintptr_t GetPageMask() {
} // namespace mozilla
int MozTaggedMemoryIsSupported(void) {
static int supported = -1;
if (supported == -1) {
// Tagging an empty range always "succeeds" if the feature is supported,
// regardless of the start pointer.
supported = mozilla::TagAnonymousMemoryAligned(nullptr, 0, nullptr) == 0;
}
return supported;
}
void MozTagAnonymousMemory(const void* aPtr, size_t aLength, const char* aTag) {
if (MozTaggedMemoryIsSupported()) {
// The kernel will round up the end of the range to the next page
// boundary if it's not aligned (comments indicate this behavior
// is based on that of madvise), but it will reject the request if
// the start is not aligned. We therefore round down the start
// address and adjust the length accordingly.
uintptr_t addr = reinterpret_cast<uintptr_t>(aPtr);
uintptr_t end = addr + aLength;
uintptr_t addrRounded = addr & mozilla::GetPageMask();
const void* ptrRounded = reinterpret_cast<const void*>(addrRounded);
// The kernel will round up the end of the range to the next page
// boundary if it's not aligned (comments indicate this behavior is
// based on that of madvise), but it will reject the request if the
// start is not aligned. We therefore round down the start address
// and adjust the length accordingly.
uintptr_t addr = reinterpret_cast<uintptr_t>(aPtr);
uintptr_t end = addr + aLength;
uintptr_t addrRounded = addr & mozilla::GetPageMask();
const void* ptrRounded = reinterpret_cast<const void*>(addrRounded);
mozilla::TagAnonymousMemoryAligned(ptrRounded, end - addrRounded, aTag);
}
// Ignore the return value. TagAnonymousMemoryAligned will harmlessly fail on
// kernels without CONFIG_ANON_VMA_NAME.
mozilla::TagAnonymousMemoryAligned(ptrRounded, end - addrRounded, aTag);
}
void* MozTaggedAnonymousMmap(void* aAddr, size_t aLength, int aProt, int aFlags,
int aFd, off_t aOffset, const char* aTag) {
void* mapped = mmap(aAddr, aLength, aProt, aFlags, aFd, aOffset);
if (MozTaggedMemoryIsSupported() &&
(aFlags & MAP_ANONYMOUS) == MAP_ANONYMOUS && mapped != MAP_FAILED) {
if ((aFlags & MAP_ANONYMOUS) == MAP_ANONYMOUS && mapped != MAP_FAILED) {
// Ignore the return value. TagAnonymousMemoryAligned will harmlessly fail
// on kernels without CONFIG_ANON_VMA_NAME.
mozilla::TagAnonymousMemoryAligned(mapped, aLength, aTag);
}
return mapped;

4
mfbt/TaggedAnonymousMemory.h
View File

@@ -55,8 +55,6 @@ MFBT_API void* MozTaggedAnonymousMmap(void* aAddr, size_t aLength, int aProt,
int aFlags, int aFd, off_t aOffset,
const char* aTag);
MFBT_API int MozTaggedMemoryIsSupported(void);
# ifdef __cplusplus
} // extern "C"
# endif
@@ -77,8 +75,6 @@ static inline void* MozTaggedAnonymousMmap(void* aAddr, size_t aLength,
# endif
}
static inline int MozTaggedMemoryIsSupported(void) { return 0; }
# endif // XP_LINUX
#endif // !XP_WIN