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[sanitizer] Warn if allocator size exceeds max user virtual address #152428

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Merged
merged 5 commits into from
Aug 7, 2025
Merged

[sanitizer] Warn if allocator size exceeds max user virtual address #152428

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[sanitizer] Warn if allocator size exceeds max user virtual address
thurstond Aug 7, 2025
9b747cd
Clarify warning
thurstond Aug 7, 2025
2478b34
Describe edge case with 48-bit video music awards
thurstond Aug 7, 2025
5948c0e
Include heap_start in check too
thurstond Aug 7, 2025
cb36339
Revise TODO
thurstond Aug 7, 2025
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17 changes: 17 additions & 0 deletions compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary64.h
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Original file line number Diff line number Diff line change
Expand Up @@ -113,6 +113,23 @@ class SizeClassAllocator64 {
// ~(uptr)0.
void Init(s32 release_to_os_interval_ms, uptr heap_start = 0) {
uptr TotalSpaceSize = kSpaceSize + AdditionalSize();

uptr MaxAddr = GetMaxUserVirtualAddress();
// VReport does not call the sanitizer allocator.
VReport(3, "Max user virtual address: 0x%zx\n", MaxAddr);
VReport(3, "Total space size for primary allocator: 0x%zx\n",
TotalSpaceSize);
// TODO: hypothetical edge case: on >48-bit VMA systems, Linux by default
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it's not immediately clear what there is TO DO

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There is nothing to do in the immediate or even medium-term future. But suppose it's the year 2800: 256TB heaps are commonplace, this warning message keeps popping up. and you get woken from cryogenic sleep because you are the last-known maintainer of Android sanitizers; you'll be glad the TODO is there to hint that the check needs revising.

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i mean: if it says TODO, it should clearly state what there is to do. if it's just an explanation of the state of things, remove the TODO.

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I've revised it

// maps as if it was a 48-bit VMA, but a sanitizer could
// theoretically map beyond the 48-bit limit (N.B. 2**48 == 256TB).
if (heap_start + TotalSpaceSize >= MaxAddr) {
// We can't easily adjust the requested heap size, because kSpaceSize is
// const (for optimization) and used throughout the code.
VReport(0, "Error: heap size %zx exceeds max user virtual address %zx\n",
TotalSpaceSize, MaxAddr);
VReport(
0, "Try using a kernel that allows a larger virtual address space\n");
}
PremappedHeap = heap_start != 0;
if (PremappedHeap) {
CHECK(!kUsingConstantSpaceBeg);
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