[dev.cc] runtime: convert signal handlers from C to Go

This code overused macros and could not be
converted automatically. Instead a new sigctxt
type had to be defined for each os/arch combination,
with a common (implicit) interface used by the
arch-specific signal handler code.

[This CL is part of the removal of C code from package runtime.
See golang.org/s/dev.cc for an overview.]

LGTM=r
R=r
CC=austin, dvyukov, golang-codereviews, iant, khr
https://codereview.appspot.com/168500044

1 files changed, 131 insertions, 0 deletions

diff --git a/src/runtime/signal_386.go b/src/runtime/signal_386.go
new file mode 100644
index 000000000..5336a4330
--- /dev/null
+++ b/src/runtime/signal_386.go
@@ -0,0 +1,131 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd
+
+package runtime
+
+import "unsafe"
+
+func dumpregs(c *sigctxt) {
+	print("eax    ", hex(c.eax()), "\n")
+	print("ebx    ", hex(c.ebx()), "\n")
+	print("ecx    ", hex(c.ecx()), "\n")
+	print("edx    ", hex(c.edx()), "\n")
+	print("edi    ", hex(c.edi()), "\n")
+	print("esi    ", hex(c.esi()), "\n")
+	print("ebp    ", hex(c.ebp()), "\n")
+	print("esp    ", hex(c.esp()), "\n")
+	print("eip    ", hex(c.eip()), "\n")
+	print("eflags ", hex(c.eflags()), "\n")
+	print("cs     ", hex(c.cs()), "\n")
+	print("fs     ", hex(c.fs()), "\n")
+	print("gs     ", hex(c.gs()), "\n")
+}
+
+func sighandler(sig uint32, info *siginfo, ctxt unsafe.Pointer, gp *g) {
+	_g_ := getg()
+	c := &sigctxt{info, ctxt}
+
+	if sig == _SIGPROF {
+		sigprof((*byte)(unsafe.Pointer(uintptr(c.eip()))), (*byte)(unsafe.Pointer(uintptr(c.esp()))), nil, gp, _g_.m)
+		return
+	}
+
+	flags := int32(_SigThrow)
+	if sig < uint32(len(sigtable)) {
+		flags = sigtable[sig].flags
+	}
+	if c.sigcode() != _SI_USER && flags&_SigPanic != 0 {
+		// Make it look like a call to the signal func.
+		// Have to pass arguments out of band since
+		// augmenting the stack frame would break
+		// the unwinding code.
+		gp.sig = sig
+		gp.sigcode0 = uintptr(c.sigcode())
+		gp.sigcode1 = uintptr(c.sigaddr())
+		gp.sigpc = uintptr(c.eip())
+
+		if GOOS == "darwin" {
+			// Work around Leopard bug that doesn't set FPE_INTDIV.
+			// Look at instruction to see if it is a divide.
+			// Not necessary in Snow Leopard (si_code will be != 0).
+			if sig == _SIGFPE && gp.sigcode0 == 0 {
+				pc := (*[4]byte)(unsafe.Pointer(gp.sigpc))
+				i := 0
+				if pc[i] == 0x66 { // 16-bit instruction prefix
+					i++
+				}
+				if pc[i] == 0xF6 || pc[i] == 0xF7 {
+					gp.sigcode0 = _FPE_INTDIV
+				}
+			}
+		}
+
+		// Only push runtime.sigpanic if rip != 0.
+		// If rip == 0, probably panicked because of a
+		// call to a nil func.  Not pushing that onto sp will
+		// make the trace look like a call to runtime.sigpanic instead.
+		// (Otherwise the trace will end at runtime.sigpanic and we
+		// won't get to see who faulted.)
+		if c.eip() != 0 {
+			sp := c.esp()
+			if regSize > ptrSize {
+				sp -= ptrSize
+				*(*uintptr)(unsafe.Pointer(uintptr(sp))) = 0
+			}
+			sp -= ptrSize
+			*(*uintptr)(unsafe.Pointer(uintptr(sp))) = uintptr(c.eip())
+			c.set_esp(sp)
+		}
+		c.set_eip(uint32(funcPC(sigpanic)))
+		return
+	}
+
+	if c.sigcode() == _SI_USER || flags&_SigNotify != 0 {
+		if sigsend(sig) {
+			return
+		}
+	}
+
+	if flags&_SigKill != 0 {
+		exit(2)
+	}
+
+	if flags&_SigThrow == 0 {
+		return
+	}
+
+	_g_.m.throwing = 1
+	_g_.m.caughtsig = gp
+	startpanic()
+
+	if sig < uint32(len(sigtable)) {
+		print(sigtable[sig].name, "\n")
+	} else {
+		print("Signal ", sig, "\n")
+	}
+
+	print("PC=", hex(c.eip()), "\n")
+	if _g_.m.lockedg != nil && _g_.m.ncgo > 0 && gp == _g_.m.g0 {
+		print("signal arrived during cgo execution\n")
+		gp = _g_.m.lockedg
+	}
+	print("\n")
+
+	var docrash bool
+	if gotraceback(&docrash) > 0 {
+		goroutineheader(gp)
+		tracebacktrap(uintptr(c.eip()), uintptr(c.esp()), 0, gp)
+		tracebackothers(gp)
+		print("\n")
+		dumpregs(c)
+	}
+
+	if docrash {
+		crash()
+	}
+
+	exit(2)
+}