text: // 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 amd64 amd64p32
  // +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
  
  #include "runtime.h"
  #include "defs_GOOS_GOARCH.h"
  #include "os_GOOS.h"
  #include "signal_GOOS_GOARCH.h"
  #include "signals_GOOS.h"
  
  void
  runtime·dumpregs(Siginfo *info, void *ctxt)
  {
  	USED(info);
  	USED(ctxt);
  	
  	runtime·printf("rax     %X\n", SIG_RAX(info, ctxt));
  	runtime·printf("rbx     %X\n", SIG_RBX(info, ctxt));
  	runtime·printf("rcx     %X\n", SIG_RCX(info, ctxt));
  	runtime·printf("rdx     %X\n", SIG_RDX(info, ctxt));
  	runtime·printf("rdi     %X\n", SIG_RDI(info, ctxt));
  	runtime·printf("rsi     %X\n", SIG_RSI(info, ctxt));
  	runtime·printf("rbp     %X\n", SIG_RBP(info, ctxt));
  	runtime·printf("rsp     %X\n", SIG_RSP(info, ctxt));
  	runtime·printf("r8      %X\n", SIG_R8(info, ctxt) );
  	runtime·printf("r9      %X\n", SIG_R9(info, ctxt) );
  	runtime·printf("r10     %X\n", SIG_R10(info, ctxt));
  	runtime·printf("r11     %X\n", SIG_R11(info, ctxt));
  	runtime·printf("r12     %X\n", SIG_R12(info, ctxt));
  	runtime·printf("r13     %X\n", SIG_R13(info, ctxt));
  	runtime·printf("r14     %X\n", SIG_R14(info, ctxt));
  	runtime·printf("r15     %X\n", SIG_R15(info, ctxt));
  	runtime·printf("rip     %X\n", SIG_RIP(info, ctxt));
  	runtime·printf("rflags  %X\n", SIG_RFLAGS(info, ctxt));
  	runtime·printf("cs      %X\n", SIG_CS(info, ctxt));
  	runtime·printf("fs      %X\n", SIG_FS(info, ctxt));
  	runtime·printf("gs      %X\n", SIG_GS(info, ctxt));
  }
  
  void
  runtime·sighandler(int32 sig, Siginfo *info, void *ctxt, G *gp)
  {
  	uintptr *sp;
  	SigTab *t;
  	bool crash;
  
  	if(sig == SIGPROF) {
  		runtime·sigprof((byte*)SIG_RIP(info, ctxt), (byte*)SIG_RSP(info, ctxt), nil, gp, g->m);
  		return;
  	}
  
  #ifdef GOOS_darwin
  	// x86-64 has 48-bit virtual addresses. The top 16 bits must echo bit 47.
  	// The hardware delivers a different kind of fault for a malformed address
  	// than it does for an attempt to access a valid but unmapped address.
  	// OS X 10.9.2 mishandles the malformed address case, making it look like
  	// a user-generated signal (like someone ran kill -SEGV ourpid).
  	// We pass user-generated signals to os/signal, or else ignore them.
  	// Doing that here - and returning to the faulting code - results in an
  	// infinite loop. It appears the best we can do is rewrite what the kernel
  	// delivers into something more like the truth. The address used below
  	// has very little chance of being the one that caused the fault, but it is
  	// malformed, it is clearly not a real pointer, and if it does get printed
  	// in real life, people will probably search for it and find this code.
  	// There are no Google hits for b01dfacedebac1e or 0xb01dfacedebac1e
  	// as I type this comment.
  	if(sig == SIGSEGV && SIG_CODE0(info, ctxt) == SI_USER) {
  		SIG_CODE0(info, ctxt) = SI_USER+1;
  		info->si_addr = (void*)(uintptr)0xb01dfacedebac1eULL;
  	}
  #endif
  
  	t = &runtime·sigtab[sig];
  	if(SIG_CODE0(info, ctxt) != SI_USER && (t->flags & SigPanic)) {
  		// 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 = SIG_CODE0(info, ctxt);
  		gp->sigcode1 = SIG_CODE1(info, ctxt);
  		gp->sigpc = SIG_RIP(info, ctxt);
  
  #ifdef 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) {
  			byte *pc;
  			pc = (byte*)gp->sigpc;
  			if((pc[0]&0xF0) == 0x40)	// 64-bit REX prefix
  				pc++;
  			else if(pc[0] == 0x66)	// 16-bit instruction prefix
  				pc++;
  			if(pc[0] == 0xF6 || pc[0] == 0xF7)
  				gp->sigcode0 = FPE_INTDIV;
  		}
  #endif
  
  		// 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(SIG_RIP(info, ctxt) != 0) {
  			sp = (uintptr*)SIG_RSP(info, ctxt);
  			if(sizeof(uintreg) > sizeof(uintptr))
  				*--sp = 0;
  			*--sp = SIG_RIP(info, ctxt);
  			SIG_RSP(info, ctxt) = (uintptr)sp;
  		}
  		SIG_RIP(info, ctxt) = (uintptr)runtime·sigpanic;
  		return;
  	}
  
  	if(SIG_CODE0(info, ctxt) == SI_USER || (t->flags & SigNotify))
  		if(runtime·sigsend(sig))
  			return;
  	if(t->flags & SigKill)
  		runtime·exit(2);
  	if(!(t->flags & SigThrow))
  		return;
  
  	g->m->throwing = 1;
  	g->m->caughtsig = gp;
  	runtime·startpanic();
  
  	if(sig < 0 || sig >= NSIG)
  		runtime·printf("Signal %d\n", sig);
  	else
  		runtime·printf("%s\n", runtime·sigtab[sig].name);
  
  	runtime·printf("PC=%X\n", SIG_RIP(info, ctxt));
  	if(g->m->lockedg != nil && g->m->ncgo > 0 && gp == g->m->g0) {
  		runtime·printf("signal arrived during cgo execution\n");
  		gp = g->m->lockedg;
  	}
  	runtime·printf("\n");
  
  	if(runtime·gotraceback(&crash)){
  		runtime·goroutineheader(gp);
  		runtime·traceback(SIG_RIP(info, ctxt), SIG_RSP(info, ctxt), 0, gp);
  		runtime·tracebackothers(gp);
  		runtime·printf("\n");
  		runtime·dumpregs(info, ctxt);
  	}
  	
  	if(crash)
  		runtime·crash();
  
  	runtime·exit(2);
  }
  