While we're here, fix Syscall9 on NetBSD and OpenBSD:
it was storing the results into the wrong memory locations.
I guess no one uses that function's results on those systems.
Part of cleaning up stack traces and argument frame information.
R=golang-dev, dvyukov
CC=golang-dev
https://golang.org/cl/11355044
Change 231af8ac63aa (CL 7314062) made runtime.enteryscall()
set m->mcache = nil, which means that we can no longer use
syscall.errstr in syscall.Syscall and syscall.Syscall6, since it
requires a new buffer to be allocated for holding the error string.
Instead, we use pre-allocated per-M storage to hold error strings
from syscalls made while in entersyscall mode, and call
runtime.findnull to calculate the lengths.
Fixes#4994.
R=rsc, rminnich, ality, dvyukov, rminnich, r
CC=golang-dev
https://golang.org/cl/7567043
syscall.Exit would originally kill only the calling
Go proc, leaving behind other procs in the
same group. This change makes syscall.Exit call
runtime·exit, which due to CL
https://golang.org/cl/5617048
will cleanly exit all the Go procs in the group.
R=golang-dev, rsc, rminnich, remyoudompheng, ality, john
CC=golang-dev, mirtchovski
https://golang.org/cl/6036051
