[compiler-rt] eeb6be1 - Sign-extend addresses in CompactRingBuffer.

[Evgenii Stepanov via llvm-commits]

Author: Evgenii Stepanov
Date: 2022-02-10T11:59:15-08:00
New Revision: eeb6be144f34158b7f9810f535b7b650390a05e3

URL: https://github.com/llvm/llvm-project/commit/eeb6be144f34158b7f9810f535b7b650390a05e3
DIFF: https://github.com/llvm/llvm-project/commit/eeb6be144f34158b7f9810f535b7b650390a05e3.diff

LOG: Sign-extend addresses in CompactRingBuffer.

Summary:
This is neccessary to support solaris/sparc9 where some userspace
addresses have all top bits set, as well as, potentially, kernel memory
on aarch64.

This change does not update the compiler side (HWASan IR pass) which
needs to be done separately for the affected targets.

Reviewers: ro, vitalybuka

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D91827

Added: 
    

Modified: 
    compiler-rt/lib/sanitizer_common/sanitizer_ring_buffer.h

Removed: 
    


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diff  --git a/compiler-rt/lib/sanitizer_common/sanitizer_ring_buffer.h b/compiler-rt/lib/sanitizer_common/sanitizer_ring_buffer.h
index 2a46e933b75d0..f22e40cac2840 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_ring_buffer.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_ring_buffer.h
@@ -86,10 +86,13 @@ class CompactRingBuffer {
   // Lower bytes store the address of the next buffer element.
   static constexpr int kPageSizeBits = 12;
   static constexpr int kSizeShift = 56;
+  static constexpr int kSizeBits = 64 - kSizeShift;
   static constexpr uptr kNextMask = (1ULL << kSizeShift) - 1;
 
   uptr GetStorageSize() const { return (long_ >> kSizeShift) << kPageSizeBits; }
 
+  static uptr SignExtend(uptr x) { return ((sptr)x) << kSizeBits >> kSizeBits; }
+
   void Init(void *storage, uptr size) {
     CHECK_EQ(sizeof(CompactRingBuffer<T>), sizeof(void *));
     CHECK(IsPowerOfTwo(size));
@@ -97,12 +100,14 @@ class CompactRingBuffer {
     CHECK_LE(size, 128 << kPageSizeBits);
     CHECK_EQ(size % 4096, 0);
     CHECK_EQ(size % sizeof(T), 0);
-    CHECK_EQ((uptr)storage % (size * 2), 0);
-    long_ = (uptr)storage | ((size >> kPageSizeBits) << kSizeShift);
+    uptr st = (uptr)storage;
+    CHECK_EQ(st % (size * 2), 0);
+    CHECK_EQ(st, SignExtend(st & kNextMask));
+    long_ = (st & kNextMask) | ((size >> kPageSizeBits) << kSizeShift);
   }
 
   void SetNext(const T *next) {
-    long_ = (long_ & ~kNextMask) | (uptr)next;
+    long_ = (long_ & ~kNextMask) | ((uptr)next & kNextMask);
   }
 
  public:
@@ -119,7 +124,7 @@ class CompactRingBuffer {
     SetNext((const T *)storage + Idx);
   }
 
-  T *Next() const { return (T *)(long_ & kNextMask); }
+  T *Next() const { return (T *)(SignExtend(long_ & kNextMask)); }
 
   void *StartOfStorage() const {
     return (void *)((uptr)Next() & ~(GetStorageSize() - 1));