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cmd/ld: fix symbol table sorting

runtime: double-check that symbol table is sorted

If the symbol table is unsorted, the binary search in findfunc
will not find its func, which will make stack traces stop early.
When the garbage collector starts using the stack tracer,
that would be a serious problem.

The unsorted symbol addresses came from from two things:

1. The symbols in an ELF object are not necessarily sorted,
   so sort them before adding them to the symbol list.

2. The __i686.get_pc_thunk.bx symbol is present in multiple
   object files and was having its address adjusted multiple
   times, producing an incorrect address in the symbol table.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/7440044
This commit is contained in:
Russ Cox 2013-02-28 16:21:58 -05:00
parent 1bf66f081f
commit 40ed753ebd
6 changed files with 129 additions and 56 deletions

View File

@ -58,70 +58,73 @@ datcmp(Sym *s1, Sym *s2)
}
Sym*
datsort(Sym *l)
listsort(Sym *l, int (*cmp)(Sym*, Sym*), int off)
{
Sym *l1, *l2, *le;
#define NEXT(l) (*(Sym**)((char*)(l)+off))
if(l == 0 || l->next == 0)
if(l == 0 || NEXT(l) == 0)
return l;
l1 = l;
l2 = l;
for(;;) {
l2 = l2->next;
l2 = NEXT(l2);
if(l2 == 0)
break;
l2 = l2->next;
l2 = NEXT(l2);
if(l2 == 0)
break;
l1 = l1->next;
l1 = NEXT(l1);
}
l2 = l1->next;
l1->next = 0;
l1 = datsort(l);
l2 = datsort(l2);
l2 = NEXT(l1);
NEXT(l1) = 0;
l1 = listsort(l, cmp, off);
l2 = listsort(l2, cmp, off);
/* set up lead element */
if(datcmp(l1, l2) < 0) {
if(cmp(l1, l2) < 0) {
l = l1;
l1 = l1->next;
l1 = NEXT(l1);
} else {
l = l2;
l2 = l2->next;
l2 = NEXT(l2);
}
le = l;
for(;;) {
if(l1 == 0) {
while(l2) {
le->next = l2;
NEXT(le) = l2;
le = l2;
l2 = l2->next;
l2 = NEXT(l2);
}
le->next = 0;
NEXT(le) = 0;
break;
}
if(l2 == 0) {
while(l1) {
le->next = l1;
NEXT(le) = l1;
le = l1;
l1 = l1->next;
l1 = NEXT(l1);
}
break;
}
if(datcmp(l1, l2) < 0) {
le->next = l1;
if(cmp(l1, l2) < 0) {
NEXT(le) = l1;
le = l1;
l1 = l1->next;
l1 = NEXT(l1);
} else {
le->next = l2;
NEXT(le) = l2;
le = l2;
l2 = l2->next;
l2 = NEXT(l2);
}
}
le->next = 0;
NEXT(le) = 0;
return l;
#undef NEXT
}
Reloc*
@ -1010,7 +1013,7 @@ dodata(void)
s->type = SDATARELRO;
}
}
datap = datsort(datap);
datap = listsort(datap, datcmp, offsetof(Sym, next));
/*
* allocate sections. list is sorted by type,

View File

@ -311,6 +311,16 @@ static int map(ElfObj*, ElfSect*);
static int readsym(ElfObj*, int i, ElfSym*, int);
static int reltype(char*, int, uchar*);
int
valuecmp(Sym *a, Sym *b)
{
if(a->value < b->value)
return -1;
if(a->value > b->value)
return +1;
return 0;
}
void
ldelf(Biobuf *f, char *pkg, int64 len, char *pn)
{
@ -541,13 +551,6 @@ ldelf(Biobuf *f, char *pkg, int64 len, char *pn)
}
s->size = sect->size;
s->align = sect->align;
if(s->type == STEXT) {
if(etextp)
etextp->next = s;
else
textp = s;
etextp = s;
}
sect->sym = s;
}
@ -583,6 +586,12 @@ ldelf(Biobuf *f, char *pkg, int64 len, char *pn)
continue;
}
s = sym.sym;
if(s->outer != S) {
if(s->dupok)
continue;
diag("%s: duplicate symbol reference: %s in both %s and %s", pn, s->name, s->outer->name, sect->sym->name);
errorexit();
}
s->sub = sect->sym->sub;
sect->sym->sub = s;
s->type = sect->sym->type | (s->type&~SMASK) | SSUB;
@ -611,7 +620,25 @@ ldelf(Biobuf *f, char *pkg, int64 len, char *pn)
p->link = nil;
p->pc = pc++;
s->text = p;
}
}
}
// Sort outer lists by address, adding to textp.
// This keeps textp in increasing address order.
for(i=0; i<obj->nsect; i++) {
s = obj->sect[i].sym;
if(s == S)
continue;
if(s->sub)
s->sub = listsort(s->sub, valuecmp, offsetof(Sym, sub));
if(s->type == STEXT) {
if(etextp)
etextp->next = s;
else
textp = s;
etextp = s;
for(s = s->sub; s != S; s = s->sub) {
etextp->next = s;
etextp = s;
}
@ -792,7 +819,7 @@ readsym(ElfObj *obj, int i, ElfSym *sym, int needSym)
// set dupok generally. See http://codereview.appspot.com/5823055/
// comment #5 for details.
if(s && sym->other == 2) {
s->type = SHIDDEN;
s->type |= SHIDDEN;
s->dupok = 1;
}
}
@ -804,14 +831,14 @@ readsym(ElfObj *obj, int i, ElfSym *sym, int needSym)
// and should only reference by its index, not name, so we
// don't bother to add them into hash table
s = newsym(sym->name, version);
s->type = SHIDDEN;
s->type |= SHIDDEN;
}
break;
case ElfSymBindWeak:
if(needSym) {
s = newsym(sym->name, 0);
if(sym->other == 2)
s->type = SHIDDEN;
s->type |= SHIDDEN;
}
break;
default:

View File

@ -593,13 +593,6 @@ ldmacho(Biobuf *f, char *pkg, int64 len, char *pn)
} else
s->type = SDATA;
}
if(s->type == STEXT) {
if(etextp)
etextp->next = s;
else
textp = s;
etextp = s;
}
sect->sym = s;
}
@ -631,6 +624,12 @@ ldmacho(Biobuf *f, char *pkg, int64 len, char *pn)
werrstr("reference to invalid section %s/%s", sect->segname, sect->name);
continue;
}
if(s->outer != S) {
if(s->dupok)
continue;
diag("%s: duplicate symbol reference: %s in both %s and %s", pn, s->name, s->outer->name, sect->sym->name);
errorexit();
}
s->type = outer->type | SSUB;
s->sub = outer->sub;
outer->sub = s;
@ -661,13 +660,31 @@ ldmacho(Biobuf *f, char *pkg, int64 len, char *pn)
p->link = nil;
p->pc = pc++;
s->text = p;
etextp->next = s;
etextp = s;
}
sym->sym = s;
}
// Sort outer lists by address, adding to textp.
// This keeps textp in increasing address order.
for(i=0; i<c->seg.nsect; i++) {
sect = &c->seg.sect[i];
if((s = sect->sym) == S)
continue;
if(s->sub)
s->sub = listsort(s->sub, valuecmp, offsetof(Sym, sub));
if(s->type == STEXT) {
if(etextp)
etextp->next = s;
else
textp = s;
etextp = s;
for(s = s->sub; s != S; s = s->sub) {
etextp->next = s;
etextp = s;
}
}
}
// load relocations
for(i=0; i<c->seg.nsect; i++) {
sect = &c->seg.sect[i];

View File

@ -236,13 +236,6 @@ ldpe(Biobuf *f, char *pkg, int64 len, char *pn)
s->p = sect->base;
s->np = sect->size;
s->size = sect->size;
if(s->type == STEXT) {
if(etextp)
etextp->next = s;
else
textp = s;
etextp = s;
}
sect->sym = s;
if(strcmp(sect->name, ".rsrc") == 0)
setpersrc(sect->sym);
@ -327,6 +320,12 @@ ldpe(Biobuf *f, char *pkg, int64 len, char *pn)
goto bad;
s = sym->sym;
if(s->outer != S) {
if(s->dupok)
continue;
diag("%s: duplicate symbol reference: %s in both %s and %s", pn, s->name, s->outer->name, sect->sym->name);
errorexit();
}
if(sym->sectnum == 0) {// extern
if(s->type == SDYNIMPORT)
s->plt = -2; // flag for dynimport in PE object files.
@ -367,9 +366,27 @@ ldpe(Biobuf *f, char *pkg, int64 len, char *pn)
p->link = nil;
p->pc = pc++;
s->text = p;
etextp->next = s;
}
}
// Sort outer lists by address, adding to textp.
// This keeps textp in increasing address order.
for(i=0; i<obj->nsect; i++) {
s = obj->sect[i].sym;
if(s == S)
continue;
if(s->sub)
s->sub = listsort(s->sub, valuecmp, offsetof(Sym, sub));
if(s->type == STEXT) {
if(etextp)
etextp->next = s;
else
textp = s;
etextp = s;
for(s = s->sub; s != S; s = s->sub) {
etextp->next = s;
etextp = s;
}
}
}

View File

@ -196,7 +196,6 @@ void deadcode(void);
Reloc* addrel(Sym*);
void codeblk(int32, int32);
void datblk(int32, int32);
Sym* datsort(Sym*);
void reloc(void);
void relocsym(Sym*);
void savedata(Sym*, Prog*, char*);
@ -238,6 +237,8 @@ void setpersrc(Sym*);
void doversion(void);
void usage(void);
void setinterp(char*);
Sym* listsort(Sym*, int(*cmp)(Sym*, Sym*), int);
int valuecmp(Sym*, Sym*);
int pathchar(void);
void* mal(uint32);

View File

@ -195,12 +195,13 @@ static int32 nfname;
static uint32 funcinit;
static Lock funclock;
static uintptr lastvalue;
static void
dofunc(Sym *sym)
{
Func *f;
switch(sym->symtype) {
case 't':
case 'T':
@ -208,6 +209,11 @@ dofunc(Sym *sym)
case 'L':
if(runtime·strcmp(sym->name, (byte*)"etext") == 0)
break;
if(sym->value < lastvalue) {
runtime·printf("symbols out of order: %p before %p\n", lastvalue, sym->value);
runtime·throw("malformed symbol table");
}
lastvalue = sym->value;
if(func == nil) {
nfunc++;
break;
@ -544,6 +550,7 @@ buildfuncs(void)
// count funcs, fnames
nfunc = 0;
nfname = 0;
lastvalue = 0;
walksymtab(dofunc);
// Initialize tables.
@ -553,6 +560,7 @@ buildfuncs(void)
func[nfunc].entry = (uint64)etext;
fname = runtime·mallocgc(nfname*sizeof fname[0], FlagNoPointers, 0, 1);
nfunc = 0;
lastvalue = 0;
walksymtab(dofunc);
// split pc/ln table by func