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Bug 1829125 - Align the PHC area to the jemalloc chunk size r=glandium

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Differential Revision: https://phabricator.services.mozilla.com/D179533
This commit is contained in:
Paul Bone 2023-07-12 09:29:02 +00:00
parent 3732a83cd1
commit e0df8952ac
2 changed files with 41 additions and 13 deletions
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memory/replace/dmd/test/script-sort-by.json.gz
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54
memory/replace/phc/PHC.cpp
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@ -298,6 +298,15 @@ static const size_t kPageSize =
#endif
;
// We align the PHC area to a multiple of the jemalloc and JS GC chunk size
// (both use 1MB aligned chunks) so that their address computations don't lead
// from non-PHC memory into PHC memory causing misleading PHC stacks to be
// attached to a crash report.
static const size_t kPhcAlign = 1024 * 1024;
static_assert(IsPowerOfTwo(kPhcAlign));
static_assert((kPhcAlign % kPageSize) == 0);
// There are two kinds of page.
// - Allocation pages, from which allocations are made.
// - Guard pages, which are never touched by PHC.
@ -310,6 +319,10 @@ static const size_t kNumAllPages = kNumAllocPages * 2 + 1;
// The total size of the allocation pages and guard pages.
static const size_t kAllPagesSize = kNumAllPages * kPageSize;
// jemalloc adds a guard page to the end of our allocation, see the comment in
// AllocAllPages() for more information.
static const size_t kAllPagesJemallocSize = kAllPagesSize - kPageSize;
// The junk value used to fill new allocation in debug builds. It's same value
// as the one used by mozjemalloc. PHC applies it unconditionally in debug
// builds. Unlike mozjemalloc, PHC doesn't consult the MALLOC_OPTIONS
@ -456,20 +469,32 @@ class GConst {
// Allocates the allocation pages and the guard pages, contiguously.
uint8_t* AllocAllPages() {
// Allocate the pages so that they are inaccessible. They are never freed,
// because it would happen at process termination when it would be of little
// use.
void* pages =
#ifdef XP_WIN
VirtualAlloc(nullptr, kAllPagesSize, MEM_RESERVE, PAGE_NOACCESS);
#else
mmap(nullptr, kAllPagesSize, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1,
0);
#endif
// The memory allocated here is never freed, because it would happen at
// process termination when it would be of little use.
// We can rely on jemalloc's behaviour that when it allocates memory aligned
// with its own chunk size it will over-allocate and guarantee that the
// memory after the end of our allocation, but before the next chunk, is
// decommitted and inaccessible. Elsewhere in PHC we assume that we own
// that page (so that memory errors in it get caught by PHC) but here we
// use kAllPagesJemallocSize which subtracts jemalloc's guard page.
void* pages = sMallocTable.memalign(kPhcAlign, kAllPagesJemallocSize);
if (!pages) {
MOZ_CRASH();
}
// Make the pages inaccessible.
#ifdef XP_WIN
if (!VirtualFree(pages, kAllPagesJemallocSize, MEM_DECOMMIT)) {
MOZ_CRASH("VirtualFree failed");
}
#else
if (mmap(pages, kAllPagesJemallocSize, PROT_NONE,
MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1, 0) == MAP_FAILED) {
MOZ_CRASH("mmap failed");
}
#endif
return static_cast<uint8_t*>(pages);
}
@ -1468,9 +1493,12 @@ void replace_jemalloc_stats(jemalloc_stats_t* aStats,
jemalloc_bin_stats_t* aBinStats) {
sMallocTable.jemalloc_stats_internal(aStats, aBinStats);
// Add all the pages to `mapped`.
size_t mapped = kAllPagesSize;
aStats->mapped += mapped;
// We allocate our memory from jemalloc so it has already counted our memory
// usage within "mapped" and "allocated", we must subtract the memory we
// allocated from jemalloc from allocated before adding in only the parts that
// we have allocated out to Firefox.
aStats->allocated -= kAllPagesJemallocSize;
size_t allocated = 0;
{