[PATCH] D53789: [hwasan] optionally right-align heap allocations

[Kostya Serebryany via Phabricator via llvm-commits]

kcc added a comment.

Atomic operations on aarch64 require alignment, so this approach will break whenever the code does something like 
struct Foo{

  AtomiWord a;  // used by atomic instructions 
  char vla[0];

} 
all other loads/stores seem to work (see "https://reviews.llvm.org/B2.5.2 Alignment of data accesses" in https://static.docs.arm.com/ddi0487/da/DDI0487D_a_armv8_arm.pdf)

so far I've found one such place (std::string implementation in libstdc++, which uses a ref counting string). 
I've also tried several benchmarks from fuzzer-test-suite with hwasan and right-alignment. 
Those that don't use std::string just work, so I think we still have a chance to get away with this on aarch64, 
although we may require some code modifications to avoid the situation above.


Repository:
  rCRT Compiler Runtime

https://reviews.llvm.org/D53789