[llvm-dev] [compiler-rt] Use of ESR context in AArch64 sigframe

[Will Deacon via llvm-dev]

Hi all,

As part of some recent work to harden the Kernel Address Space Layout
Randomisation (KASLR) implementation in arm64 Linux, I've proposed a
patch for the kernel which omits the ESR context from the signal frame
if the faulting virtual address is outside the range of addresses which
can be mapped by userspace.

http://lists.infradead.org/pipermail/linux-arm-kernel/2018-March/563837.html

Looking around, it seems that AddressSanitizer is using this information
in compiler-rt in order to distinguish the faulting access type between
READ, WRITE or UNKNOWN. With this change, all attempted accesses to kernel
memory from userspace will be reported as UNKNOWN.

Is this likely to cause a problem?

Many thanks,

Will