[libunwind] Replace process_vm_readv with SYS_rt_sigprocmask (#74791)
process_vm_readv is generally considered dangerous from a syscall
perspective, and is frequently blanket banned in seccomp filters such as
those in Chromium and ChromiumOS. We can get the same behaviour during
the invalid PC address case with the raw SYS_rt_sigprocmask syscall.
Testing to ensure that process_vm_readv does not appear, I ran the
output of check-unwind on an ARM64 device under strace. Previously,
bad_unwind_info in particular would use process_vm_readv, but with this
commit, it now no longer uses it:
```
strace test/Output/bad_unwind_info.pass.cpp.dir/t.tmp.exe \
|& grep process_vm_readv
```
The libunwind unittests were also tested on ARM64 ChromeOS (Gentoo
Linux) devices.
GitOrigin-RevId: fc1c478709e380164733560e4a2c8f9e8d5e2c1c
1 file changed
