From: Alberto Donizetti Date: Thu, 3 May 2018 08:13:31 +0000 (+0200) Subject: runtime: ignore sigaction error on Linux if it is for SIGRTMAX X-Git-Tag: go1.11beta1~527 X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=2aef675000e71daeef77c0fb3379bcd142e48959;p=gostls13.git runtime: ignore sigaction error on Linux if it is for SIGRTMAX The Go runtime registers a handler for every signal. This prevents Go binaries from working on QEMU in user-emulation mode, since the hacky way QEMU implements signals on Linux assumes that no-one uses signal 64 (SIGRTMAX). In the past, we had a workaround in the runtime to prevent crashes on start-up when running on QEMU: golang.org/cl/124900043 golang.org/cl/16853 but it went lost during the 1.11 dev cycle. More precisely, the test for SIGRTMAX was dropped in CL 18150 when we stopped testing the result of sigaction in the Linux implementation of setsig. That change was made to avoid a stack split overflow because code started calling setsig from nosplit functions. Then in CL 99077 we started testing the result of sigaction again, this time using systemstack to avoid to stack split overflow. When this test was added back, we did not bring back the test of SIGRTMAX. As a result, Go1.10 binaries work on QEMU, while 1.11 binaries immediately crash on startup. This change restores the QEMU workaround. Updates #24656 Change-Id: I46380b1e1b4bf47db7bc7b3d313f00c4e4c11ea3 Reviewed-on: https://go-review.googlesource.com/111176 Reviewed-by: Ian Lance Taylor --- diff --git a/src/runtime/os_linux.go b/src/runtime/os_linux.go index a4992343b5..68f99de115 100644 --- a/src/runtime/os_linux.go +++ b/src/runtime/os_linux.go @@ -415,10 +415,14 @@ func (c *sigctxt) fixsigcode(sig uint32) { //go:nosplit func sysSigaction(sig uint32, new, old *sigactiont) { if rt_sigaction(uintptr(sig), new, old, unsafe.Sizeof(sigactiont{}.sa_mask)) != 0 { - // Use system stack to avoid split stack overflow on ppc64/ppc64le. - systemstack(func() { - throw("sigaction failed") - }) + // Workaround for bug in Qemu user mode emulation. (qemu + // rejects rt_sigaction of signal 64, SIGRTMAX). + if sig != 64 { + // Use system stack to avoid split stack overflow on ppc64/ppc64le. + systemstack(func() { + throw("sigaction failed") + }) + } } }