[PATCH] D68794: libhwasan initialisation include kernel syscall ABI relaxation

[Evgenii Stepanov via Phabricator via llvm-commits]

eugenis added a comment.

In D68794#1705862 <https://reviews.llvm.org/D68794#1705862>, @mmalcomson wrote:

> Run `prctl` syscall for Android, but ignore EINVAL failures.
>
> NOTE: I don't believe this distinguishes between running on a kernel with with the tagged address ABI unconditional or running on a newer kernel or on a kernel with `sysctl abi.tagged_addr_disabled=1`
>  (https://android.googlesource.com/kernel/common/+/690c4ca8a5715644370384672f24d95b042db74a/Documentation/arm64/tagged-address-abi.rst)


This is a good point. It appears that PR_GET_TAGGED_ADDR_CTRL works even when abi.tagged_addr_disabled=1, we can use it to tell these two cases apart, but there is not a lot we could do with that information.

A real test would be invoking a random syscall with a tagged pointer, ex. uname(). I don't think we need to go that far, but leaving it up to you.



================
Comment at: compiler-rt/lib/hwasan/hwasan.cpp:357
 
+  InitPrctl();
+
----------------
Please move it to InitInstrumentation to handle __hwasan_init_static, too.


================
Comment at: compiler-rt/lib/hwasan/hwasan_linux.cpp:157
+#define PR_TAGGED_ADDR_ENABLE  (1UL << 0)
+  if (prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0) == -1
+      || ! prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0)) {
----------------
This needs to be internal_prctl because prctl implementation in libc can be built with hwasan.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D68794/new/

https://reviews.llvm.org/D68794