[PATCH] D105629: [TSan] Add SystemZ support

Tue Jul 13 03:33:37 PDT 2021

uweigand added inline comments.

================
Comment at: compiler-rt/lib/tsan/rtl/tsan_platform_posix.cpp:123
+#if defined(__s390x__)
+  ProtectRange(HiAppMemEnd(), 0xfffffffffffff000ull);
+#endif
----------------
iii wrote:
> uweigand wrote:
> > iii wrote:
> > > uweigand wrote:
> > > > Did you test this on older kernels without 5-level page table support?   I believe the allocation / mprotect may fail on those ...
> > > No, not really. Would it make sense to probe here? E.g. first try 0xfffffffffffff000, then 0x20000000000000. Or is there a way to query user_addr_max() / TASK_SIZE_MAX / TASK_SIZE?
> > I don't know of any way to query this.  You can simply do the allocation in stages (first to the top of the three-pagetable range, then four, then five), and ignore failures.   As an unfortunate side effect this will force the kernel to allocate five levels of page tables even when unnecessary, but I don't think there's anything we can do about that.
> 3-level page table limit is quite below the application range defined in this series (0x40000000000 < 0xc00000000000). Are there any relevant kernels that do not support 4-level page tables? I tried to search the git history, and it looks as if even 2.6 ones have it.
Ah, right.  Yes, we can certainly assume 4-level support at this point.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D105629/new/

https://reviews.llvm.org/D105629