runtime: move panic/defer/recover-related stuff to a separate file

Move panic/defer/recover-related stuff from proc.c/runtime.c to a new file panic.c.
No semantic changes.
proc.c is 1800+ LOC and is a bit difficult to work with.

R=golang-dev, dave, r
CC=golang-dev
https://golang.org/cl/6343071

1 files changed, 392 insertions, 0 deletions

diff --git a/src/pkg/runtime/panic.c b/src/pkg/runtime/panic.c
new file mode 100644
index 0000000000..c2166cc0b4
--- /dev/null
+++ b/src/pkg/runtime/panic.c
@@ -0,0 +1,392 @@
+// Copyright 2012 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.
+
+#include "runtime.h"
+#include "arch_GOARCH.h"
+#include "stack.h"
+
+// Code related to defer, panic and recover.
+
+uint32 runtime·panicking;
+static Lock paniclk;
+
+// Create a new deferred function fn with siz bytes of arguments.
+// The compiler turns a defer statement into a call to this.
+// Cannot split the stack because it assumes that the arguments
+// are available sequentially after &fn; they would not be
+// copied if a stack split occurred.  It's OK for this to call
+// functions that split the stack.
+#pragma textflag 7
+uintptr
+runtime·deferproc(int32 siz, byte* fn, ...)
+{
+	Defer *d;
+	int32 mallocsiz;
+
+	mallocsiz = sizeof(*d);
+	if(siz > sizeof(d->args))
+		mallocsiz += siz - sizeof(d->args);
+	d = runtime·malloc(mallocsiz);
+	d->fn = fn;
+	d->siz = siz;
+	d->pc = runtime·getcallerpc(&siz);
+	if(thechar == '5')
+		d->argp = (byte*)(&fn+2);  // skip caller's saved link register
+	else
+		d->argp = (byte*)(&fn+1);
+	runtime·memmove(d->args, d->argp, d->siz);
+
+	d->link = g->defer;
+	g->defer = d;
+
+	// deferproc returns 0 normally.
+	// a deferred func that stops a panic
+	// makes the deferproc return 1.
+	// the code the compiler generates always
+	// checks the return value and jumps to the
+	// end of the function if deferproc returns != 0.
+	return 0;
+}
+
+// Run a deferred function if there is one.
+// The compiler inserts a call to this at the end of any
+// function which calls defer.
+// If there is a deferred function, this will call runtime·jmpdefer,
+// which will jump to the deferred function such that it appears
+// to have been called by the caller of deferreturn at the point
+// just before deferreturn was called.  The effect is that deferreturn
+// is called again and again until there are no more deferred functions.
+// Cannot split the stack because we reuse the caller's frame to
+// call the deferred function.
+#pragma textflag 7
+void
+runtime·deferreturn(uintptr arg0)
+{
+	Defer *d;
+	byte *argp, *fn;
+
+	d = g->defer;
+	if(d == nil)
+		return;
+	argp = (byte*)&arg0;
+	if(d->argp != argp)
+		return;
+	runtime·memmove(argp, d->args, d->siz);
+	g->defer = d->link;
+	fn = d->fn;
+	if(!d->nofree)
+		runtime·free(d);
+	runtime·jmpdefer(fn, argp);
+}
+
+// Run all deferred functions for the current goroutine.
+static void
+rundefer(void)
+{
+	Defer *d;
+
+	while((d = g->defer) != nil) {
+		g->defer = d->link;
+		reflect·call(d->fn, (byte*)d->args, d->siz);
+		if(!d->nofree)
+			runtime·free(d);
+	}
+}
+
+// Print all currently active panics.  Used when crashing.
+static void
+printpanics(Panic *p)
+{
+	if(p->link) {
+		printpanics(p->link);
+		runtime·printf("\t");
+	}
+	runtime·printf("panic: ");
+	runtime·printany(p->arg);
+	if(p->recovered)
+		runtime·printf(" [recovered]");
+	runtime·printf("\n");
+}
+
+static void recovery(G*);
+
+// The implementation of the predeclared function panic.
+void
+runtime·panic(Eface e)
+{
+	Defer *d;
+	Panic *p;
+
+	p = runtime·mal(sizeof *p);
+	p->arg = e;
+	p->link = g->panic;
+	p->stackbase = (byte*)g->stackbase;
+	g->panic = p;
+
+	for(;;) {
+		d = g->defer;
+		if(d == nil)
+			break;
+		// take defer off list in case of recursive panic
+		g->defer = d->link;
+		g->ispanic = true;	// rock for newstack, where reflect.call ends up
+		reflect·call(d->fn, (byte*)d->args, d->siz);
+		if(p->recovered) {
+			g->panic = p->link;
+			if(g->panic == nil)	// must be done with signal
+				g->sig = 0;
+			runtime·free(p);
+			// put recovering defer back on list
+			// for scheduler to find.
+			d->link = g->defer;
+			g->defer = d;
+			runtime·mcall(recovery);
+			runtime·throw("recovery failed"); // mcall should not return
+		}
+		if(!d->nofree)
+			runtime·free(d);
+	}
+
+	// ran out of deferred calls - old-school panic now
+	runtime·startpanic();
+	printpanics(g->panic);
+	runtime·dopanic(0);
+}
+
+// Unwind the stack after a deferred function calls recover
+// after a panic.  Then arrange to continue running as though
+// the caller of the deferred function returned normally.
+static void
+recovery(G *gp)
+{
+	Defer *d;
+
+	// Rewind gp's stack; we're running on m->g0's stack.
+	d = gp->defer;
+	gp->defer = d->link;
+
+	// Unwind to the stack frame with d's arguments in it.
+	runtime·unwindstack(gp, d->argp);
+
+	// Make the deferproc for this d return again,
+	// this time returning 1.  The calling function will
+	// jump to the standard return epilogue.
+	// The -2*sizeof(uintptr) makes up for the
+	// two extra words that are on the stack at
+	// each call to deferproc.
+	// (The pc we're returning to does pop pop
+	// before it tests the return value.)
+	// On the arm there are 2 saved LRs mixed in too.
+	if(thechar == '5')
+		gp->sched.sp = (uintptr)d->argp - 4*sizeof(uintptr);
+	else
+		gp->sched.sp = (uintptr)d->argp - 2*sizeof(uintptr);
+	gp->sched.pc = d->pc;
+	if(!d->nofree)
+		runtime·free(d);
+	runtime·gogo(&gp->sched, 1);
+}
+
+// Free stack frames until we hit the last one
+// or until we find the one that contains the sp.
+void
+runtime·unwindstack(G *gp, byte *sp)
+{
+	Stktop *top;
+	byte *stk;
+
+	// Must be called from a different goroutine, usually m->g0.
+	if(g == gp)
+		runtime·throw("unwindstack on self");
+
+	while((top = (Stktop*)gp->stackbase) != nil && top->stackbase != nil) {
+		stk = (byte*)gp->stackguard - StackGuard;
+		if(stk <= sp && sp < (byte*)gp->stackbase)
+			break;
+		gp->stackbase = (uintptr)top->stackbase;
+		gp->stackguard = (uintptr)top->stackguard;
+		if(top->free != 0)
+			runtime·stackfree(stk, top->free);
+	}
+
+	if(sp != nil && (sp < (byte*)gp->stackguard - StackGuard || (byte*)gp->stackbase < sp)) {
+		runtime·printf("recover: %p not in [%p, %p]\n", sp, gp->stackguard - StackGuard, gp->stackbase);
+		runtime·throw("bad unwindstack");
+	}
+}
+
+// The implementation of the predeclared function recover.
+// Cannot split the stack because it needs to reliably
+// find the stack segment of its caller.
+#pragma textflag 7
+void
+runtime·recover(byte *argp, Eface ret)
+{
+	Stktop *top, *oldtop;
+	Panic *p;
+
+	// Must be a panic going on.
+	if((p = g->panic) == nil || p->recovered)
+		goto nomatch;
+
+	// Frame must be at the top of the stack segment,
+	// because each deferred call starts a new stack
+	// segment as a side effect of using reflect.call.
+	// (There has to be some way to remember the
+	// variable argument frame size, and the segment
+	// code already takes care of that for us, so we
+	// reuse it.)
+	//
+	// As usual closures complicate things: the fp that
+	// the closure implementation function claims to have
+	// is where the explicit arguments start, after the
+	// implicit pointer arguments and PC slot.
+	// If we're on the first new segment for a closure,
+	// then fp == top - top->args is correct, but if
+	// the closure has its own big argument frame and
+	// allocated a second segment (see below),
+	// the fp is slightly above top - top->args.
+	// That condition can't happen normally though
+	// (stack pointers go down, not up), so we can accept
+	// any fp between top and top - top->args as
+	// indicating the top of the segment.
+	top = (Stktop*)g->stackbase;
+	if(argp < (byte*)top - top->argsize || (byte*)top < argp)
+		goto nomatch;
+
+	// The deferred call makes a new segment big enough
+	// for the argument frame but not necessarily big
+	// enough for the function's local frame (size unknown
+	// at the time of the call), so the function might have
+	// made its own segment immediately.  If that's the
+	// case, back top up to the older one, the one that
+	// reflect.call would have made for the panic.
+	//
+	// The fp comparison here checks that the argument
+	// frame that was copied during the split (the top->args
+	// bytes above top->fp) abuts the old top of stack.
+	// This is a correct test for both closure and non-closure code.
+	oldtop = (Stktop*)top->stackbase;
+	if(oldtop != nil && top->argp == (byte*)oldtop - top->argsize)
+		top = oldtop;
+
+	// Now we have the segment that was created to
+	// run this call.  It must have been marked as a panic segment.
+	if(!top->panic)
+		goto nomatch;
+
+	// Okay, this is the top frame of a deferred call
+	// in response to a panic.  It can see the panic argument.
+	p->recovered = 1;
+	ret = p->arg;
+	FLUSH(&ret);
+	return;
+
+nomatch:
+	ret.type = nil;
+	ret.data = nil;
+	FLUSH(&ret);
+}
+
+void
+runtime·startpanic(void)
+{
+	if(m->dying) {
+		runtime·printf("panic during panic\n");
+		runtime·exit(3);
+	}
+	m->dying = 1;
+	runtime·xadd(&runtime·panicking, 1);
+	runtime·lock(&paniclk);
+}
+
+void
+runtime·dopanic(int32 unused)
+{
+	static bool didothers;
+
+	if(g->sig != 0)
+		runtime·printf("[signal %x code=%p addr=%p pc=%p]\n",
+			g->sig, g->sigcode0, g->sigcode1, g->sigpc);
+
+	if(runtime·gotraceback()){
+		if(g != m->g0) {
+			runtime·printf("\n");
+			runtime·goroutineheader(g);
+			runtime·traceback(runtime·getcallerpc(&unused), runtime·getcallersp(&unused), 0, g);
+		}
+		if(!didothers) {
+			didothers = true;
+			runtime·tracebackothers(g);
+		}
+	}
+	runtime·unlock(&paniclk);
+	if(runtime·xadd(&runtime·panicking, -1) != 0) {
+		// Some other m is panicking too.
+		// Let it print what it needs to print.
+		// Wait forever without chewing up cpu.
+		// It will exit when it's done.
+		static Lock deadlock;
+		runtime·lock(&deadlock);
+		runtime·lock(&deadlock);
+	}
+
+	runtime·exit(2);
+}
+
+void
+runtime·panicindex(void)
+{
+	runtime·panicstring("index out of range");
+}
+
+void
+runtime·panicslice(void)
+{
+	runtime·panicstring("slice bounds out of range");
+}
+
+void
+runtime·throwreturn(void)
+{
+	// can only happen if compiler is broken
+	runtime·throw("no return at end of a typed function - compiler is broken");
+}
+
+void
+runtime·throwinit(void)
+{
+	// can only happen with linker skew
+	runtime·throw("recursive call during initialization - linker skew");
+}
+
+void
+runtime·throw(int8 *s)
+{
+	runtime·startpanic();
+	runtime·printf("throw: %s\n", s);
+	runtime·dopanic(0);
+	*(int32*)0 = 0;	// not reached
+	runtime·exit(1);	// even more not reached
+}
+
+void
+runtime·panicstring(int8 *s)
+{
+	Eface err;
+
+	if(m->gcing) {
+		runtime·printf("panic: %s\n", s);
+		runtime·throw("panic during gc");
+	}
+	runtime·newErrorString(runtime·gostringnocopy((byte*)s), &err);
+	runtime·panic(err);
+}
+
+void
+runtime·Goexit(void)
+{
+	rundefer();
+	runtime·goexit();
+}