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[ext-code-space] Fix CodeRange hint logic on Windows and Linux

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Windows requires additional writable page to be allocated in front of
the code range, but at the same time the code range must not cross 4 GB
boundary in order to make Code pointer compression work for Code
pointers. All these constraints make the logic of hint calculation too
dependent on what VirtualMemoryCage::InitReservation() would do with
the provided hint. This CL simplifies the hint calculation and fully
relies on VirtualMemoryCage::InitReservation() to do the right thing.

On Linux the implementation of OS::GetFreeMemoryRangesWithin() doesn't
work when Chromium sandbox is enabled, so we use the beginning of the
preferred short builtin calls region as a hint. It should be at least
as good as the fallback hint but with higher chances to point to free
address space location.

Bug: v8:11880
Change-Id: I0b6ebec98dd0cf483f67e6ba8a919deb9ce7cc25
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3380585
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78568}
This commit is contained in:
Igor Sheludko 2022-01-11 14:29:03 +01:00 committed by V8 LUCI CQ
parent 3e0fad5aeb
commit 4ecd70a284
1 changed files with 6 additions and 9 deletions
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15
src/heap/code-range.cc
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@ -53,6 +53,11 @@ Address CodeRangeAddressHint::GetAddressHint(size_t code_range_size,
CHECK(IsAligned(result, alignment));
return result;
}
// The empty memory_ranges means that GetFreeMemoryRangesWithin() API
// is not supported, so use the lowest address from the preferred region
// as a hint because it'll be at least as good as the fallback hint but
// with a higher chances to point to the free address space range.
return RoundUp(preferred_region.begin(), alignment);
}
return RoundUp(FUNCTION_ADDR(&FunctionInStaticBinaryForAddressHint),
alignment);
@ -124,16 +129,8 @@ bool CodeRange::InitReservation(v8::PageAllocator* page_allocator,
: VirtualMemoryCage::ReservationParams::kAnyBaseAlignment;
params.base_bias_size = RoundUp(reserved_area, allocate_page_size);
params.page_size = MemoryChunk::kPageSize;
// V8_EXTERNAL_CODE_SPACE imposes additional alignment requirement for the
// base address, so make sure the hint calculation function takes that into
// account. Otherwise the allocated reservation might be outside of the
// preferred region (see Isolate::GetShortBuiltinsCallRegion()).
const size_t hint_alignment =
V8_EXTERNAL_CODE_SPACE_BOOL
? RoundUp(params.base_alignment, allocate_page_size)
: allocate_page_size;
params.requested_start_hint =
GetCodeRangeAddressHint()->GetAddressHint(requested, hint_alignment);
GetCodeRangeAddressHint()->GetAddressHint(requested, allocate_page_size);
if (!VirtualMemoryCage::InitReservation(params)) return false;