From 294963fb7f8983c7f5560dc20ab75c869f30da14 Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Wed, 22 Nov 2017 21:58:57 -0500 Subject: [PATCH] runtime: document sigtrampgo better Add an explanation of why sigtrampgo is nosplit. Updates #21314. Change-Id: I3f5909d2b2c180f9fa74d53df13e501826fd4316 Reviewed-on: https://go-review.googlesource.com/79615 Reviewed-by: Ian Lance Taylor --- src/runtime/signal_unix.go | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/src/runtime/signal_unix.go b/src/runtime/signal_unix.go index a616d46bacf..9dae058f2cd 100644 --- a/src/runtime/signal_unix.go +++ b/src/runtime/signal_unix.go @@ -275,6 +275,12 @@ func sigpipe() { // sigtrampgo is called from the signal handler function, sigtramp, // written in assembly code. // This is called by the signal handler, and the world may be stopped. +// +// It must be nosplit because getg() is still the G that was running +// (if any) when the signal was delivered, but it's (usually) called +// on the gsignal stack. Until this switches the G to gsignal, the +// stack bounds check won't work. +// //go:nosplit //go:nowritebarrierrec func sigtrampgo(sig uint32, info *siginfo, ctx unsafe.Pointer) {