[compiler-rt] r353482 - [safestack] Explain why tinfo at the end of the buffer

[Vitaly Buka via llvm-commits]

Author: vitalybuka
Date: Thu Feb  7 15:20:47 2019
New Revision: 353482

URL: http://llvm.org/viewvc/llvm-project?rev=353482&view=rev
Log:
[safestack] Explain why tinfo at the end of the buffer

Reviewers: pcc, eugenis, vlad.tsyrklevich

Reviewed By: vlad.tsyrklevich

Subscribers: llvm-commits, jfb, #sanitizers

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D57863

Modified:
    compiler-rt/trunk/lib/safestack/safestack.cc

Modified: compiler-rt/trunk/lib/safestack/safestack.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/safestack/safestack.cc?rev=353482&r1=353481&r2=353482&view=diff
==============================================================================
--- compiler-rt/trunk/lib/safestack/safestack.cc (original)
+++ compiler-rt/trunk/lib/safestack/safestack.cc Thu Feb  7 15:20:47 2019
@@ -228,6 +228,8 @@ INTERCEPTOR(int, pthread_create, pthread
   size = RoundUpTo(size, kStackAlign);
 
   void *addr = unsafe_stack_alloc(size, guard);
+  // Put tinfo at the end of the buffer. guard may be not page aligned.
+  // If that is so then some bytes after addr can be mprotected.
   struct tinfo *tinfo =
       (struct tinfo *)(((char *)addr) + size - sizeof(struct tinfo));
   tinfo->start_routine = start_routine;