61 lines
2.8 KiB
Diff
61 lines
2.8 KiB
Diff
From fb77ca05ffb4f8e666878f2f6718a9fb4d686839 Mon Sep 17 00:00:00 2001
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From: Thurston Dang <thurston@google.com>
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Date: Thu, 13 Apr 2023 23:55:01 +0000
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Subject: [PATCH] Re-land 'ASan: move allocator base to avoid conflict with
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high-entropy ASLR for x86-64 Linux'
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D147984 was reverted because it broke lit tests on Mac. This revision is based on D147984
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but maintains the old behavior for Apple.
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Note that, per the follow-up discussion with MaskRay in D147984, this patch excludes Apple
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but includes other platforms (e.g., aarch64, MIPS64) and OSes (e.g., FreeBSD, S390X), not just
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x86-64 Linux.
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Original commit message from D147984:
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Users have discovered [*] that when CONFIG_ARCH_MMAP_RND_BITS == 32,
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it will frequently conflict with ASan's allocator on x86-64 Linux, because the
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PIE program segment base address of 0x555555555554 plus an ASLR shift of up to
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((2**32) * 4K == 0x100000000000) will sometimes exceed ASan's hardcoded
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base address of 0x600000000000. We fix this by simply moving the allocator base
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to 0x500000000000, which is below the PIE program segment base address. This is
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cleaner than trying to move it to another location that is sandwiched between
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the PIE program and library segments, because if either of those grow too large,
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it will collide with the allocator region.
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Note that we will never need to change this base address again (unless we want to increase
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the size of the allocator), because ASLR cannot be set above 32-bits for x86-64 Linux (the
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PIE program segment and library segments would collide with each other; see also
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ARCH_MMAP_RND_BITS_MAX in https://github.com/torvalds/linux/blob/master/arch/x86/Kconfig).
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[*] see https://b.corp.google.com/issues/276925478
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and https://groups.google.com/a/google.com/g/chrome-os-gardeners/c/BbfzCP3dEeo/m/h3C_vVUxCQAJ
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Differential Revision: https://reviews.llvm.org/D148280
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---
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compiler-rt/lib/asan/asan_allocator.h | 8 ++++++--
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1 file changed, 6 insertions(+), 2 deletions(-)
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diff --git a/compiler-rt/lib/asan/asan_allocator.h b/compiler-rt/lib/asan/asan_allocator.h
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index 0b4dbf03bb9d5..6a12a6c602528 100644
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--- a/compiler-rt/lib/asan/asan_allocator.h
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+++ b/compiler-rt/lib/asan/asan_allocator.h
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@@ -143,11 +143,15 @@ typedef DefaultSizeClassMap SizeClassMap;
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const uptr kAllocatorSpace = ~(uptr)0;
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const uptr kAllocatorSize = 0x8000000000ULL; // 500G
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typedef DefaultSizeClassMap SizeClassMap;
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-# else
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+# elif SANITIZER_APPLE
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const uptr kAllocatorSpace = 0x600000000000ULL;
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const uptr kAllocatorSize = 0x40000000000ULL; // 4T.
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typedef DefaultSizeClassMap SizeClassMap;
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-# endif
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+# else
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+const uptr kAllocatorSpace = 0x500000000000ULL;
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+const uptr kAllocatorSize = 0x40000000000ULL; // 4T.
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+typedef DefaultSizeClassMap SizeClassMap;
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+# endif
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template <typename AddressSpaceViewTy>
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struct AP64 { // Allocator64 parameters. Deliberately using a short name.
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static const uptr kSpaceBeg = kAllocatorSpace;
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