use pc/ln table to print source lines in traceback

r45=; 6.out
oops
panic PC=0x400316
0x400316?zi /home/rsc/go/src/runtime/rt0_amd64_linux.s:83
	main·g(4195177, 0, 4205661, ...)
	main·g(0x400369, 0x402c5d, 0x403e49, ...)
0x40034c?zi /home/rsc/go/src/runtime/x.go:24
	main·f(4205661, 0, 4210249, ...)
	main·f(0x402c5d, 0x403e49, 0x1, ...)
0x400368?zi /home/rsc/go/src/runtime/x.go:37
	main·main(4210249, 0, 1, ...)
	main·main(0x403e49, 0x1, 0x7fff9d894bd8, ...)
0x402c5c?zi /home/rsc/go/src/runtime/rt0_amd64.s:70
	mainstart(1, 0, 2643020760, ...)
	mainstart(0x1, 0x7fff9d894bd8, 0x0, ...)
r45=;

R=r
DELTA=251  (198 added, 25 deleted, 28 changed)
OCL=19965
CL=19979

src/runtime/rt2_amd64.c

@@ -11,8 +11,6 @@ extern uint8 end;
 void
 traceback(uint8 *pc, uint8 *sp, void* r15)
 {
-	int32 spoff;
-	int8* spp;
 	uint8* callpc;
 	int32 counter;
 	int32 i;
@@ -60,7 +58,11 @@ traceback(uint8 *pc, uint8 *sp, void* r15)
 		/* print this frame */
 		prints("0x");
 		sys·printpointer(callpc  - 1);	// -1 to get to CALL instr.
-		prints("?zi\n");
+		prints("?zi ");
+		sys·printstring(f->src);
+		prints(":");
+		sys·printint(funcline(f, (uint64)callpc-1));	// -1 to get to CALL instr.
+		prints("\n");
 		prints("\t");
 		sys·printstring(name);
 		prints("(");

src/runtime/runtime.h

@@ -189,9 +189,13 @@ struct	SigTab
 struct	Func
 {
 	string	name;
-	string	type;
+	string	type;	// go type string
-	uint64	entry;
+	string	src;	// src file name
-	int64	frame;
+	uint64	entry;	// entry pc
+	int64	frame;	// stack frame size
+	Array	pcln;	// pc/ln tab for this func
+	int64	pc0;	// starting pc, ln for table
+	int32	ln0;
 };
 
 /*
@@ -261,6 +265,7 @@ void	signalstack(byte*, int32);
 G*	malg(int32);
 void	minit(void);
 Func*	findfunc(uint64);
+int32	funcline(Func*, uint64);
 
 /*
  * mutual exclusion locks.  in the uncontended case,

src/runtime/symtab.c

@@ -2,21 +2,22 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-#include "runtime.h"
+// Runtime symbol table access.  Work in progress.
+// The Plan 9 symbol table is not in a particularly convenient form.
+// The routines here massage it into a more usable form; eventually
+// we'll change 6l to do this for us, but it is easier to experiment
+// here than to change 6l and all the other tools.
+//
+// The symbol table also needs to be better integrated with the type
+// strings table in the future.  This is just a quick way to get started
+// and figure out exactly what we want.
 
-// Runtime symbol table access.
+#include "runtime.h"
-// Very much a work in progress.
 
 #define SYMCOUNTS ((int32*)(0x99LL<<32))	// known to 6l
 #define SYMDATA ((byte*)(0x99LL<<32) + 8)
 
 // Return a pointer to a byte array containing the symbol table segment.
-//
-// NOTE(rsc): I expect that we will clean up both the method of getting
-// at the symbol table and the exact format of the symbol table at some
-// point in the future.  It probably needs to be better integrated with
-// the type strings table too.  This is just a quick way to get started
-// and figure out what we want from/can do with it.
 void
 sys·symdat(Array *symtab, Array *pclntab)
 {
@@ -50,7 +51,7 @@ struct Sym
 };
 
 // Walk over symtab, calling fn(&s) for each symbol.
-void
+static void
 walksymtab(void (*fn)(Sym*))
 {
 	int32 *v;
@@ -68,10 +69,10 @@ walksymtab(void (*fn)(Sym*))
 			break;
 		s.symtype = p[4] & ~0x80;
 		p += 5;
+		s.name = p;
 		if(s.symtype == 'z' || s.symtype == 'Z') {
 			// path reference string - skip first byte,
 			// then 2-byte pairs ending at two zeros.
-			// for now, just skip over it and ignore it.
 			q = p+1;
 			for(;;) {
 				if(q+2 > ep)
@@ -81,12 +82,10 @@ walksymtab(void (*fn)(Sym*))
 				q += 2;
 			}
 			p = q+2;
-			s.name = nil;
 		}else{
 			q = mchr(p, '\0', ep);
 			if(q == nil)
 				break;
-			s.name = p;
 			p = q+1;
 		}
 		q = mchr(p, '\0', ep);
@@ -100,33 +99,198 @@ walksymtab(void (*fn)(Sym*))
 
 // Symtab walker; accumulates info about functions.
 
-Func *func;
+static Func *func;
-int32 nfunc;
+static int32 nfunc;
+
+static byte **fname;
+static int32 nfname;
 
 static void
 dofunc(Sym *sym)
 {
-	static byte *lastfuncname;
-	static Func *lastfunc;
 	Func *f;
 
-	if(lastfunc && sym->symtype == 'm') {
+	switch(sym->symtype) {
-		lastfunc->frame = sym->value;
+	case 't':
-		return;
+	case 'T':
-	}
-	if(sym->symtype != 'T' && sym->symtype != 't')
-		return;
 		if(strcmp(sym->name, (byte*)"etext") == 0)
-		return;
+			break;
 		if(func == nil) {
 			nfunc++;
-		return;
+			break;
 		}
-
 		f = &func[nfunc++];
 		f->name = gostring(sym->name);
 		f->entry = sym->value;
-	lastfunc = f;
+		break;
+	case 'm':
+		if(nfunc > 0 && func != nil)
+			func[nfunc-1].frame = sym->value;
+		break;
+	case 'f':
+		if(fname == nil) {
+			if(sym->value >= nfname)
+				nfname = sym->value+1;
+			break;
+		}
+		fname[sym->value] = sym->name;
+		break;
+	}
+}
+
+// put together the path name for a z entry.
+// the f entries have been accumulated into fname already.
+static void
+makepath(byte *buf, int32 nbuf, byte *path)
+{
+	int32 n, len;
+	byte *p, *ep, *q;
+
+	if(nbuf <= 0)
+		return;
+
+	p = buf;
+	ep = buf + nbuf;
+	*p = '\0';
+	for(;;) {
+		if(path[0] == 0 && path[1] == 0)
+			break;
+		n = (path[0]<<8) | path[1];
+		path += 2;
+		if(n >= nfname)
+			break;
+		q = fname[n];
+		len = findnull(q);
+		if(p+1+len >= ep)
+			break;
+		if(p > buf && p[-1] != '/')
+			*p++ = '/';
+		mcpy(p, q, len+1);
+		p += len;
+	}
+}
+
+// walk symtab accumulating path names for use by pc/ln table.
+// don't need the full generality of the z entry history stack because
+// there are no includes in go (and only sensible includes in our c).
+static void
+dosrcline(Sym *sym)
+{
+	static byte srcbuf[1000];
+	static string srcstring;
+	static int32 lno, incstart;
+	static int32 nf, nhist;
+	Func *f;
+
+	switch(sym->symtype) {
+	case 't':
+	case 'T':
+		f = &func[nf++];
+		f->src = srcstring;
+		f->ln0 += lno;
+		break;
+	case 'z':
+		if(sym->value == 1) {
+			// entry for main source file for a new object.
+			makepath(srcbuf, sizeof srcbuf, sym->name+1);
+			srcstring = gostring(srcbuf);
+			lno = 0;
+			nhist = 0;
+		} else {
+			// push or pop of included file.
+			makepath(srcbuf, sizeof srcbuf, sym->name+1);
+			if(srcbuf[0] != '\0') {
+				if(nhist++ == 0)
+					incstart = sym->value;
+			}else{
+				if(--nhist == 0)
+					lno -= sym->value - incstart;
+			}
+		}
+	}
+}
+
+enum { PcQuant = 1 };
+
+// Interpret pc/ln table, saving the subpiece for each func.
+static void
+splitpcln(void)
+{
+	int32 line;
+	uint64 pc;
+	byte *p, *ep;
+	Func *f, *ef;
+	int32 *v;
+
+	// pc/ln table bounds
+	v = SYMCOUNTS;
+	p = SYMDATA;
+	p += v[0];
+	ep = p+v[1];
+
+	f = func;
+	ef = func + nfunc;
+	f->pcln.array = p;
+	pc = func[0].entry;	// text base
+	line = 0;
+	for(; p < ep; p++) {
+		if(f < ef && pc >= (f+1)->entry) {
+			f->pcln.nel = p - f->pcln.array;
+			f->pcln.cap = f->pcln.nel;
+			f++;
+			f->pcln.array = p;
+			f->pc0 = pc;
+			f->ln0 = line;
+		}
+		if(*p == 0) {
+			// 4 byte add to line
+			line += (p[1]<<24) | (p[2]<<16) | (p[3]<<8) | p[4];
+			p += 4;
+		} else if(*p <= 64) {
+			line += *p;
+		} else if(*p <= 128) {
+			line -= *p - 64;
+		} else {
+			pc += PcQuant*(*p - 129);
+		}
+		pc += PcQuant;
+	}
+	if(f < ef) {
+		f->pcln.nel = p - f->pcln.array;
+		f->pcln.cap = f->pcln.nel;
+	}
+}
+
+
+// Return actual file line number for targetpc in func f.
+// (Source file is f->src.)
+int32
+funcline(Func *f, uint64 targetpc)
+{
+	byte *p, *ep;
+	uint64 pc;
+	int32 line;
+
+	p = f->pcln.array;
+	ep = p + f->pcln.nel;
+	pc = f->pc0;
+	line = f->ln0;
+	for(; p < ep; p++) {
+		if(pc >= targetpc)
+			return line;
+		if(*p == 0) {
+			line += (p[1]<<24) | (p[2]<<16) | (p[3]<<8) | p[4];
+			p += 4;
+		} else if(*p <= 64) {
+			line += *p;
+		} else if(*p <= 128) {
+			line -= *p - 64;
+		} else {
+			pc += PcQuant*(*p - 129);
+		}
+		pc += PcQuant;
+	}
+	return line;
 }
 
 static void
@@ -136,19 +300,30 @@ buildfuncs(void)
 
 	if(func != nil)
 		return;
+	// count funcs, fnames
 	nfunc = 0;
+	nfname = 0;
 	walksymtab(dofunc);
+
+	// initialize tables
 	func = mal((nfunc+1)*sizeof func[0]);
+	func[nfunc].entry = (uint64)etext;
+	fname = mal(nfname*sizeof fname[0]);
 	nfunc = 0;
 	walksymtab(dofunc);
-	func[nfunc].entry = (uint64)etext;
+
+	// split pc/ln table by func
+	splitpcln();
+
+	// record src file and line info for each func
+	walksymtab(dosrcline);
 }
 
 Func*
 findfunc(uint64 addr)
 {
 	Func *f;
-	int32 i, nf, n;
+	int32 nf, n;
 
 	if(func == nil)
 		buildfuncs();
@@ -157,15 +332,6 @@ findfunc(uint64 addr)
 	if(addr < func[0].entry || addr >= func[nfunc].entry)
 		return nil;
 
-	// linear search, for debugging
-	if(0) {
-		for(i=0; i<nfunc; i++) {
-			if(func[i].entry <= addr && addr < func[i+1].entry)
-				return &func[i];
-		}
-		return nil;
-	}
-
 	// binary search to find func with entry <= addr.
 	f = func;
 	nf = nfunc;