src/libmach/dwarfpc.c - plan9 - Git at Google

 /*
  * Dwarf pc to source line conversion.
  *
  * Maybe should do the reverse here, but what should the interface look like?
  * One possibility is to use the Plan 9 line2addr interface:
  *
  *	long line2addr(ulong line, ulong basepc)
  *
  * which returns the smallest pc > basepc with line number line (ignoring file name).
  *
  * The encoding may be small, but it sure isn't simple!
  */

 #include <u.h>
 #include <libc.h>
 #include <bio.h>
 #include "elf.h"
 #include "dwarf.h"

 #define trace 0

 enum
 {
 	Isstmt = 1<<0,
 	BasicDwarfBlock = 1<<1,
 	EndSequence = 1<<2,
 	PrologueEnd = 1<<3,
 	EpilogueBegin = 1<<4
 };

 typedef struct State State;
 struct State
 {
 	ulong addr;
 	ulong file;
 	ulong line;
 	ulong column;
 	ulong flags;
 	ulong isa;
 };

 int
 dwarfpctoline(Dwarf *d, ulong pc, char **cdir, char **dir, char **file, ulong *line, ulong *mtime, ulong *length)
 {
 	uchar *prog, *opcount, *end;
 	ulong off, unit, len, vers, x, start;
 	int i, first, op, a, l, quantum, isstmt, linebase, linerange, opcodebase, nf;
 	char *files, *dirs, *s;
 	DwarfBuf b;
 	DwarfSym sym;
 	State emit, cur, reset;
 	uchar **f, **newf;

 	f = nil;

 	if(dwarfaddrtounit(d, pc, &unit) < 0
 	|| dwarflookuptag(d, unit, TagCompileUnit, &sym) < 0)
 		return -1;

 	if(!sym.attrs.have.stmtlist){
 		werrstr("no line mapping information for 0x%lux", pc);
 		return -1;
 	}
 	off = sym.attrs.stmtlist;
 	if(off >= d->line.len){
 		fprint(2, "bad stmtlist\n");
 		goto bad;
 	}

 	if(trace) fprint(2, "unit 0x%lux stmtlist 0x%lux\n", unit, sym.attrs.stmtlist);

 	memset(&b, 0, sizeof b);
 	b.d = d;
 	b.p = d->line.data + off;
 	b.ep = b.p + d->line.len;
 	b.addrsize = sym.b.addrsize;	/* should i get this from somewhere else? */

 	len = dwarfget4(&b);
 	if(b.p==nil || b.p+len > b.ep || b.p+len < b.p){
 		fprint(2, "bad len\n");
 		goto bad;
 	}

 	b.ep = b.p+len;
 	vers = dwarfget2(&b);
 	if(vers != 2){
 		werrstr("bad dwarf version 0x%lux", vers);
 		return -1;
 	}

 	len = dwarfget4(&b);
 	if(b.p==nil || b.p+len > b.ep || b.p+len < b.p){
 		fprint(2, "another bad len\n");
 		goto bad;
 	}
 	prog = b.p+len;

 	quantum = dwarfget1(&b);
 	isstmt = dwarfget1(&b);
 	linebase = (schar)dwarfget1(&b);
 	linerange = (schar)dwarfget1(&b);
 	opcodebase = dwarfget1(&b);

 	opcount = b.p-1;
 	dwarfgetnref(&b, opcodebase-1);
 	if(b.p == nil){
 		fprint(2, "bad opcode chart\n");
 		goto bad;
 	}

 	/* just skip the files and dirs for now; we'll come back */
 	dirs = (char*)b.p;
 	while(b.p!=nil && *b.p!=0)
 		dwarfgetstring(&b);
 	dwarfget1(&b);

 	files = (char*)b.p;
 	while(b.p!=nil && *b.p!=0){
 		dwarfgetstring(&b);
 		dwarfget128(&b);
 		dwarfget128(&b);
 		dwarfget128(&b);
 	}
 	dwarfget1(&b);

 	/* move on to the program */
 	if(b.p == nil || b.p > prog){
 		fprint(2, "bad header\n");
 		goto bad;
 	}
 	b.p = prog;

 	reset.addr = 0;
 	reset.file = 1;
 	reset.line = 1;
 	reset.column = 0;
 	reset.flags = isstmt ? Isstmt : 0;
 	reset.isa = 0;

 	cur = reset;
 	emit = reset;
 	nf = 0;
 	start = 0;
 	if(trace) fprint(2, "program @ %lud ... %.*H opbase = %d\n", b.p - d->line.data, b.ep-b.p, b.p, opcodebase);
 	first = 1;
 	while(b.p != nil){
 		op = dwarfget1(&b);
 		if(trace) fprint(2, "\tline %lud, addr 0x%lux, op %d %.10H", cur.line, cur.addr, op, b.p);
 		if(op >= opcodebase){
 			a = (op - opcodebase) / linerange;
 			l = (op - opcodebase) % linerange + linebase;
 			cur.line += l;
 			cur.addr += a * quantum;
 			if(trace) fprint(2, " +%d,%d\n", a, l);
 		emit:
 			if(first){
 				if(cur.addr > pc){
 					werrstr("found wrong line mapping 0x%lux for pc 0x%lux", cur.addr, pc);
 					goto out;
 				}
 				first = 0;
 				start = cur.addr;
 			}
 			if(cur.addr > pc)
 				break;
 			if(b.p == nil){
 				werrstr("buffer underflow in line mapping");
 				goto out;
 			}
 			emit = cur;
 			if(emit.flags & EndSequence){
 				werrstr("found wrong line mapping 0x%lux-0x%lux for pc 0x%lux", start, cur.addr, pc);
 				goto out;
 			}
 			cur.flags &= ~(BasicDwarfBlock|PrologueEnd|EpilogueBegin);
 		}else{
 			switch(op){
 			case 0:	/* extended op code */
 				if(trace) fprint(2, " ext");
 				len = dwarfget128(&b);
 				end = b.p+len;
 				if(b.p == nil || end > b.ep || end < b.p || len < 1)
 					goto bad;
 				switch(dwarfget1(&b)){
 				case 1:	/* end sequence */
 					if(trace) fprint(2, " end\n");
 					cur.flags |= EndSequence;
 					goto emit;
 				case 2:	/* set address */
 					cur.addr = dwarfgetaddr(&b);
 					if(trace) fprint(2, " set pc 0x%lux\n", cur.addr);
 					break;
 				case 3:	/* define file */
 					newf = realloc(f, (nf+1)*sizeof(f[0]));
 					if(newf == nil)
 						goto out;
 					f = newf;
 					f[nf++] = b.p;
 					s = dwarfgetstring(&b);
 					dwarfget128(&b);
 					dwarfget128(&b);
 					dwarfget128(&b);
 					if(trace) fprint(2, " def file %s\n", s);
 					break;
 				}
 				if(b.p == nil || b.p > end)
 					goto bad;
 				b.p = end;
 				break;
 			case 1:	/* emit */
 				if(trace) fprint(2, " emit\n");
 				goto emit;
 			case 2:	/* advance pc */
 				a = dwarfget128(&b);
 				if(trace) fprint(2, " advance pc + %lud\n", a*quantum);
 				cur.addr += a * quantum;
 				break;
 			case 3:	/* advance line */
 				l = dwarfget128s(&b);
 				if(trace) fprint(2, " advance line + %ld\n", l);
 				cur.line += l;
 				break;
 			case 4:	/* set file */
 				if(trace) fprint(2, " set file\n");
 				cur.file = dwarfget128s(&b);
 				break;
 			case 5:	/* set column */
 				if(trace) fprint(2, " set column\n");
 				cur.column = dwarfget128(&b);
 				break;
 			case 6:	/* negate stmt */
 				if(trace) fprint(2, " negate stmt\n");
 				cur.flags ^= Isstmt;
 				break;
 			case 7:	/* set basic block */
 				if(trace) fprint(2, " set basic block\n");
 				cur.flags |= BasicDwarfBlock;
 				break;
 			case 8:	/* const add pc */
 				a = (255 - opcodebase) / linerange * quantum;
 				if(trace) fprint(2, " const add pc + %d\n", a);
 				cur.addr += a;
 				break;
 			case 9:	/* fixed advance pc */
 				a = dwarfget2(&b);
 				if(trace) fprint(2, " fixed advance pc + %d\n", a);
 				cur.addr += a;
 				break;
 			case 10:	/* set prologue end */
 				if(trace) fprint(2, " set prologue end\n");
 				cur.flags |= PrologueEnd;
 				break;
 			case 11:	/* set epilogue begin */
 				if(trace) fprint(2, " set epilogue begin\n");
 				cur.flags |= EpilogueBegin;
 				break;
 			case 12:	/* set isa */
 				if(trace) fprint(2, " set isa\n");
 				cur.isa = dwarfget128(&b);
 				break;
 			default:	/* something new - skip it */
 				if(trace) fprint(2, " unknown %d\n", opcount[op]);
 				for(i=0; i<opcount[op]; i++)
 					dwarfget128(&b);
 				break;
 			}
 		}
 	}
 	if(b.p == nil)
 		goto bad;

 	/* finally!  the data we seek is in "emit" */

 	if(emit.file == 0){
 		werrstr("invalid file index in mapping data");
 		goto out;
 	}
 	if(line)
 		*line = emit.line;

 	/* skip over first emit.file-2 guys */
 	b.p = (uchar*)files;
 	for(i=emit.file-1; i > 0 && b.p!=nil && *b.p!=0; i--){
 		dwarfgetstring(&b);
 		dwarfget128(&b);
 		dwarfget128(&b);
 		dwarfget128(&b);
 	}
 	if(b.p == nil){
 		werrstr("problem parsing file data second time (cannot happen)");
 		goto bad;
 	}
 	if(*b.p == 0){
 		if(i >= nf){
 			werrstr("bad file index in mapping data");
 			goto bad;
 		}
 		b.p = f[i];
 	}
 	s = dwarfgetstring(&b);
 	if(file)
 		*file = s;
 	i = dwarfget128(&b);		/* directory */
 	x = dwarfget128(&b);
 	if(mtime)
 		*mtime = x;
 	x = dwarfget128(&b);
 	if(length)
 		*length = x;

 	/* fetch dir name */
 	if(cdir)
 		*cdir = sym.attrs.compdir;

 	if(dir){
 		if(i == 0)
 			*dir = nil;
 		else{
 			b.p = (uchar*)dirs;
 			for(i--; i>0 && b.p!=nil && *b.p!=0; i--)
 				dwarfgetstring(&b);
 			if(b.p==nil || *b.p==0){
 				werrstr("bad directory reference in line mapping");
 				goto out;		/* can only happen with bad dir index */
 			}
 			*dir = dwarfgetstring(&b);
 		}
 	}

 	/* free at last, free at last */
 	free(f);
 	return 0;

 bad:
 	werrstr("corrupted line mapping for 0x%lux", pc);
 out:
 	free(f);
 	return -1;
 }
	/*
	* Dwarf pc to source line conversion.
	*
	* Maybe should do the reverse here, but what should the interface look like?
	* One possibility is to use the Plan 9 line2addr interface:
	*
	* long line2addr(ulong line, ulong basepc)
	*
	* which returns the smallest pc > basepc with line number line (ignoring file name).
	*
	* The encoding may be small, but it sure isn't simple!
	*/

	#include <u.h>
	#include <libc.h>
	#include <bio.h>
	#include "elf.h"
	#include "dwarf.h"

	#define trace 0

	enum
	{
	Isstmt = 1<<0,
	BasicDwarfBlock = 1<<1,
	EndSequence = 1<<2,
	PrologueEnd = 1<<3,
	EpilogueBegin = 1<<4
	};

	typedef struct State State;
	struct State
	{
	ulong addr;
	ulong file;
	ulong line;
	ulong column;
	ulong flags;
	ulong isa;
	};

	int
	dwarfpctoline(Dwarf d, ulong pc, char cdir, char dir, char file, ulong line, ulong mtime, ulong length)
	{
	uchar prog, opcount, *end;
	ulong off, unit, len, vers, x, start;
	int i, first, op, a, l, quantum, isstmt, linebase, linerange, opcodebase, nf;
	char files, dirs, *s;
	DwarfBuf b;
	DwarfSym sym;
	State emit, cur, reset;
	uchar f, newf;

	f = nil;

	if(dwarfaddrtounit(d, pc, &unit) < 0
	\|\| dwarflookuptag(d, unit, TagCompileUnit, &sym) < 0)
	return -1;

	if(!sym.attrs.have.stmtlist){
	werrstr("no line mapping information for 0x%lux", pc);
	return -1;
	}
	off = sym.attrs.stmtlist;
	if(off >= d->line.len){
	fprint(2, "bad stmtlist\n");
	goto bad;
	}

	if(trace) fprint(2, "unit 0x%lux stmtlist 0x%lux\n", unit, sym.attrs.stmtlist);

	memset(&b, 0, sizeof b);
	b.d = d;
	b.p = d->line.data + off;
	b.ep = b.p + d->line.len;
	b.addrsize = sym.b.addrsize; /* should i get this from somewhere else? */

	len = dwarfget4(&b);
	if(b.p==nil \|\| b.p+len > b.ep \|\| b.p+len < b.p){
	fprint(2, "bad len\n");
	goto bad;
	}

	b.ep = b.p+len;
	vers = dwarfget2(&b);
	if(vers != 2){
	werrstr("bad dwarf version 0x%lux", vers);
	return -1;
	}

	len = dwarfget4(&b);
	if(b.p==nil \|\| b.p+len > b.ep \|\| b.p+len < b.p){
	fprint(2, "another bad len\n");
	goto bad;
	}
	prog = b.p+len;

	quantum = dwarfget1(&b);
	isstmt = dwarfget1(&b);
	linebase = (schar)dwarfget1(&b);
	linerange = (schar)dwarfget1(&b);
	opcodebase = dwarfget1(&b);

	opcount = b.p-1;
	dwarfgetnref(&b, opcodebase-1);
	if(b.p == nil){
	fprint(2, "bad opcode chart\n");
	goto bad;
	}

	/* just skip the files and dirs for now; we'll come back */
	dirs = (char*)b.p;
	while(b.p!=nil && *b.p!=0)
	dwarfgetstring(&b);
	dwarfget1(&b);

	files = (char*)b.p;
	while(b.p!=nil && *b.p!=0){
	dwarfgetstring(&b);
	dwarfget128(&b);
	dwarfget128(&b);
	dwarfget128(&b);
	}
	dwarfget1(&b);

	/* move on to the program */
	if(b.p == nil \|\| b.p > prog){
	fprint(2, "bad header\n");
	goto bad;
	}
	b.p = prog;

	reset.addr = 0;
	reset.file = 1;
	reset.line = 1;
	reset.column = 0;
	reset.flags = isstmt ? Isstmt : 0;
	reset.isa = 0;

	cur = reset;
	emit = reset;
	nf = 0;
	start = 0;
	if(trace) fprint(2, "program @ %lud ... %.*H opbase = %d\n", b.p - d->line.data, b.ep-b.p, b.p, opcodebase);
	first = 1;
	while(b.p != nil){
	op = dwarfget1(&b);
	if(trace) fprint(2, "\tline %lud, addr 0x%lux, op %d %.10H", cur.line, cur.addr, op, b.p);
	if(op >= opcodebase){
	a = (op - opcodebase) / linerange;
	l = (op - opcodebase) % linerange + linebase;
	cur.line += l;
	cur.addr += a * quantum;
	if(trace) fprint(2, " +%d,%d\n", a, l);
	emit:
	if(first){
	if(cur.addr > pc){
	werrstr("found wrong line mapping 0x%lux for pc 0x%lux", cur.addr, pc);
	goto out;
	}
	first = 0;
	start = cur.addr;
	}
	if(cur.addr > pc)
	break;
	if(b.p == nil){
	werrstr("buffer underflow in line mapping");
	goto out;
	}
	emit = cur;
	if(emit.flags & EndSequence){
	werrstr("found wrong line mapping 0x%lux-0x%lux for pc 0x%lux", start, cur.addr, pc);
	goto out;
	}
	cur.flags &= ~(BasicDwarfBlock\|PrologueEnd\|EpilogueBegin);
	}else{
	switch(op){
	case 0: /* extended op code */
	if(trace) fprint(2, " ext");
	len = dwarfget128(&b);
	end = b.p+len;
	if(b.p == nil \|\| end > b.ep \|\| end < b.p \|\| len < 1)
	goto bad;
	switch(dwarfget1(&b)){
	case 1: /* end sequence */
	if(trace) fprint(2, " end\n");
	cur.flags \|= EndSequence;
	goto emit;
	case 2: /* set address */
	cur.addr = dwarfgetaddr(&b);
	if(trace) fprint(2, " set pc 0x%lux\n", cur.addr);
	break;
	case 3: /* define file */
	newf = realloc(f, (nf+1)*sizeof(f[0]));
	if(newf == nil)
	goto out;
	f = newf;
	f[nf++] = b.p;
	s = dwarfgetstring(&b);
	dwarfget128(&b);
	dwarfget128(&b);
	dwarfget128(&b);
	if(trace) fprint(2, " def file %s\n", s);
	break;
	}
	if(b.p == nil \|\| b.p > end)
	goto bad;
	b.p = end;
	break;
	case 1: /* emit */
	if(trace) fprint(2, " emit\n");
	goto emit;
	case 2: /* advance pc */
	a = dwarfget128(&b);
	if(trace) fprint(2, " advance pc + %lud\n", a*quantum);
	cur.addr += a * quantum;
	break;
	case 3: /* advance line */
	l = dwarfget128s(&b);
	if(trace) fprint(2, " advance line + %ld\n", l);
	cur.line += l;
	break;
	case 4: /* set file */
	if(trace) fprint(2, " set file\n");
	cur.file = dwarfget128s(&b);
	break;
	case 5: /* set column */
	if(trace) fprint(2, " set column\n");
	cur.column = dwarfget128(&b);
	break;
	case 6: /* negate stmt */
	if(trace) fprint(2, " negate stmt\n");
	cur.flags ^= Isstmt;
	break;
	case 7: /* set basic block */
	if(trace) fprint(2, " set basic block\n");
	cur.flags \|= BasicDwarfBlock;
	break;
	case 8: /* const add pc */
	a = (255 - opcodebase) / linerange * quantum;
	if(trace) fprint(2, " const add pc + %d\n", a);
	cur.addr += a;
	break;
	case 9: /* fixed advance pc */
	a = dwarfget2(&b);
	if(trace) fprint(2, " fixed advance pc + %d\n", a);
	cur.addr += a;
	break;
	case 10: /* set prologue end */
	if(trace) fprint(2, " set prologue end\n");
	cur.flags \|= PrologueEnd;
	break;
	case 11: /* set epilogue begin */
	if(trace) fprint(2, " set epilogue begin\n");
	cur.flags \|= EpilogueBegin;
	break;
	case 12: /* set isa */
	if(trace) fprint(2, " set isa\n");
	cur.isa = dwarfget128(&b);
	break;
	default: /* something new - skip it */
	if(trace) fprint(2, " unknown %d\n", opcount[op]);
	for(i=0; i<opcount[op]; i++)
	dwarfget128(&b);
	break;
	}
	}
	}
	if(b.p == nil)
	goto bad;

	/* finally! the data we seek is in "emit" */

	if(emit.file == 0){
	werrstr("invalid file index in mapping data");
	goto out;
	}
	if(line)
	*line = emit.line;

	/* skip over first emit.file-2 guys */
	b.p = (uchar*)files;
	for(i=emit.file-1; i > 0 && b.p!=nil && *b.p!=0; i--){
	dwarfgetstring(&b);
	dwarfget128(&b);
	dwarfget128(&b);
	dwarfget128(&b);
	}
	if(b.p == nil){
	werrstr("problem parsing file data second time (cannot happen)");
	goto bad;
	}
	if(*b.p == 0){
	if(i >= nf){
	werrstr("bad file index in mapping data");
	goto bad;
	}
	b.p = f[i];
	}
	s = dwarfgetstring(&b);
	if(file)
	*file = s;
	i = dwarfget128(&b); /* directory */
	x = dwarfget128(&b);
	if(mtime)
	*mtime = x;
	x = dwarfget128(&b);
	if(length)
	*length = x;

	/* fetch dir name */
	if(cdir)
	*cdir = sym.attrs.compdir;

	if(dir){
	if(i == 0)
	*dir = nil;
	else{
	b.p = (uchar*)dirs;
	for(i--; i>0 && b.p!=nil && *b.p!=0; i--)
	dwarfgetstring(&b);
	if(b.p==nil \|\| *b.p==0){
	werrstr("bad directory reference in line mapping");
	goto out; /* can only happen with bad dir index */
	}
	*dir = dwarfgetstring(&b);
	}
	}

	/* free at last, free at last */
	free(f);
	return 0;

	bad:
	werrstr("corrupted line mapping for 0x%lux", pc);
	out:
	free(f);
	return -1;
	}