[compiler-rt] 36b52c3 - [sanitizer] Compare against the alignment of the latter range trying to find consecutive TLS blocks in GetStaticTlsBoundary

[Fangrui Song via llvm-commits]

Author: Xi Ruoyao
Date: 2022-07-17T00:45:15-07:00
New Revision: 36b52c38aaffa3cd1936b7992fffd0cfa6d67f7b

URL: https://github.com/llvm/llvm-project/commit/36b52c38aaffa3cd1936b7992fffd0cfa6d67f7b
DIFF: https://github.com/llvm/llvm-project/commit/36b52c38aaffa3cd1936b7992fffd0cfa6d67f7b.diff

LOG: [sanitizer] Compare against the alignment of the latter range trying to find consecutive TLS blocks in GetStaticTlsBoundary

On a mips64el-linux-gnu system, the dynamic linker arranges TLS blocks
like:

    [0] 0xfff7fe9680..0xfff7fe9684, align = 0x4
    [1] 0xfff7fe9688..0xfff7fe96a8, align = 0x8
    [2] 0xfff7fe96c0..0xfff7fe9e60, align = 0x40
    [3] 0xfff7fe9e60..0xfff7fe9ef8, align = 0x8

Note that the dynamic linker can only put [1] at 0xfff7fe9688, not
0xfff7fe9684 or it will be misaligned.  But we were comparing the
distance between two blocks with the alignment of the previous range,
causing GetStaticTlsBoundary fail to merge the consecutive blocks.

Compare against the alignment of the latter range to fix the issue.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D129112

Added: 
    

Modified: 
    compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp
index 9bf14ef64731..e0e4488c5b5d 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_linux_libcdep.cpp
@@ -395,14 +395,14 @@ __attribute__((unused)) static void GetStaticTlsBoundary(uptr *addr, uptr *size,
     return;
   }
   // Find the maximum consecutive ranges. We consider two modules consecutive if
-  // the gap is smaller than the alignment. The dynamic loader places static TLS
-  // blocks this way not to waste space.
+  // the gap is smaller than the alignment of the latter range. The dynamic
+  // loader places static TLS blocks this way not to waste space.
   uptr l = one;
   *align = ranges[l].align;
-  while (l != 0 && ranges[l].begin < ranges[l - 1].end + ranges[l - 1].align)
+  while (l != 0 && ranges[l].begin < ranges[l - 1].end + ranges[l].align)
     *align = Max(*align, ranges[--l].align);
   uptr r = one + 1;
-  while (r != len && ranges[r].begin < ranges[r - 1].end + ranges[r - 1].align)
+  while (r != len && ranges[r].begin < ranges[r - 1].end + ranges[r].align)
     *align = Max(*align, ranges[r++].align);
   *addr = ranges[l].begin;
   *size = ranges[r - 1].end - ranges[l].begin;