From 0d2f5c0e3b4cddd4bd8349169e0c29e0862b44e3 Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Thu, 27 Feb 2014 22:43:47 -0500 Subject: [release-branch.go1.2] runtime: if traceback sees a breakpoint, don't change the PC MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit ««« CL 49580044 / 38cd458b1dfe runtime: if traceback sees a breakpoint, don't change the PC Changing the PC confuses gdb, because execution does not continue where gdb expects it. Not changing the PC has the potential to confuse a stack dump, but when running under gdb it seems better to confuse a stack dump than to confuse gdb. Fixes #6776. LGTM=rsc R=golang-codereviews, dvyukov, rsc CC=golang-codereviews https://golang.org/cl/49580044 »»» LGTM=r R=golang-codereviews, r CC=golang-dev https://golang.org/cl/69800043 --- src/pkg/runtime/sys_x86.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/src/pkg/runtime/sys_x86.c b/src/pkg/runtime/sys_x86.c index e68ff514a2..0df6dfbbd3 100644 --- a/src/pkg/runtime/sys_x86.c +++ b/src/pkg/runtime/sys_x86.c @@ -37,6 +37,19 @@ runtime·rewindmorestack(Gobuf *gobuf) gobuf->pc = gobuf->pc + 2 + *(int8*)(pc+1); return; } + if(pc[0] == 0xcc) { + // This is a breakpoint inserted by gdb. We could use + // runtime·findfunc to find the function. But if we + // do that, then we will continue execution at the + // function entry point, and we will not hit the gdb + // breakpoint. So for this case we don't change + // gobuf->pc, so that when we return we will execute + // the jump instruction and carry on. This means that + // stack unwinding may not work entirely correctly + // (http://golang.org/issue/5723) but the user is + // running under gdb anyhow. + return; + } runtime·printf("runtime: pc=%p %x %x %x %x %x\n", pc, pc[0], pc[1], pc[2], pc[3], pc[4]); runtime·throw("runtime: misuse of rewindmorestack"); } -- cgit v1.2.3-54-g00ecf