Replace the confusing game where a frame size of $-8 would suppress the
implicit setting up of a stack frame with a nice explicit flag.
The code to set up the function prologue is still a little confusing but better
than it was.
Change-Id: I1d49278ff42c6bc734ebfb079998b32bc53f8d9a
Reviewed-on: https://go-review.googlesource.com/15670
Reviewed-by: Minux Ma <minux@golang.org>
This doesn't test much with gccgo, but at least it builds now, and the
test does, unsurprisingly, pass. A proper test would require adding
assembly files in GCC syntax for all platforms that gccgo supports,
which would be infeasible.
Also added copyright headers to the asm files.
Change-Id: Icea5af29d7d521a0681506ddb617a79705b76d33
Reviewed-on: https://go-review.googlesource.com/9417
Reviewed-by: Minux Ma <minux@golang.org>
These signals are used by glibc to broadcast setuid/setgid to all
threads and to send pthread cancellations. Unlike other signals, the
Go runtime does not intercept these because they must invoke the libc
handlers (see issues #3871 and #6997). However, because 1) these
signals may be issued asynchronously by a thread running C code to
another thread running Go code and 2) glibc does not set SA_ONSTACK
for its handlers, glibc's signal handler may be run on a Go stack.
Signal frames range from 1.5K on amd64 to many kilobytes on ppc64, so
this may overflow the Go stack and corrupt heap (or other stack) data.
Fix this by ensuring that these signal handlers have the SA_ONSTACK
flag (but not otherwise taking over the handler).
This has been a problem since Go 1.1, but it's likely that people
haven't encountered it because it only affects setuid/setgid and
pthread_cancel.
Fixes#9600.
Change-Id: I6cf5f5c2d3aa48998d632f61f1ddc2778dcfd300
Reviewed-on: https://go-review.googlesource.com/1887
Reviewed-by: Ian Lance Taylor <iant@golang.org>
