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[wasm] Fix 4GB max memory pages on 32-bit platforms

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When a reservation of exactly 4GB is requested on a 32-bit platform,
we can simply pretend that we tried and failed.

Fixed: chromium:1107234
Change-Id: I9a3f4dbd31064aff620337aa291768fe47174fb4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2308346
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68968}
This commit is contained in:
Jakob Kummerow 2020-07-21 15:54:09 +02:00 committed by Commit Bot
parent 82e29d8af8
commit 7c967c3103
1 changed files with 11 additions and 8 deletions
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19
src/objects/backing-store.cc
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@ -275,6 +275,13 @@ std::unique_ptr<BackingStore> BackingStore::Allocate(
return std::unique_ptr<BackingStore>(result);
}
// Trying to allocate 4 GiB on a 32-bit platform is guaranteed to fail.
// We don't lower the official max_maximum_mem_pages() limit because that
// would be observable upon instantiation; this way the effective limit
// on 32-bit platforms is defined by the allocator.
constexpr size_t kPlatformMaxPages =
std::numeric_limits<size_t>::max() / wasm::kWasmPageSize;
void BackingStore::SetAllocatorFromIsolate(Isolate* isolate) {
if (auto allocator_shared = isolate->array_buffer_allocator_shared()) {
holds_shared_ptr_to_allocator_ = true;
@ -320,6 +327,9 @@ std::unique_ptr<BackingStore> BackingStore::TryAllocateWasmMemory(
size_t engine_max_pages = wasm::max_maximum_mem_pages();
maximum_pages = std::min(engine_max_pages, maximum_pages);
// If the platform doesn't support so many pages, attempting to allocate
// is guaranteed to fail, so we don't even try.
if (maximum_pages > kPlatformMaxPages) return {};
CHECK_LE(maximum_pages,
std::numeric_limits<size_t>::max() / wasm::kWasmPageSize);
size_t byte_capacity = maximum_pages * wasm::kWasmPageSize;
@ -417,14 +427,7 @@ std::unique_ptr<BackingStore> BackingStore::AllocateWasmMemory(
// Enforce engine limitation on the maximum number of pages.
if (initial_pages > wasm::kV8MaxWasmMemoryPages) return nullptr;
// Trying to allocate 4 GiB on a 32-bit platform is guaranteed to fail.
// We don't lower the official max_maximum_mem_pages() limit because that
// would be observable upon instantiation; this way the effective limit
// on 32-bit platforms is defined by the allocator.
constexpr size_t kPlatformMax =
std::numeric_limits<size_t>::max() / wasm::kWasmPageSize;
if (initial_pages > kPlatformMax) return nullptr;
if (initial_pages > kPlatformMaxPages) return nullptr;
auto backing_store =
TryAllocateWasmMemory(isolate, initial_pages, maximum_pages, shared);