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https://github.com/golang/go
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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
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@ -58,70 +58,73 @@ datcmp(Sym *s1, Sym *s2)
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}
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Sym*
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datsort(Sym *l)
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listsort(Sym *l, int (*cmp)(Sym*, Sym*), int off)
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{
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Sym *l1, *l2, *le;
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#define NEXT(l) (*(Sym**)((char*)(l)+off))
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if(l == 0 || l->next == 0)
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if(l == 0 || NEXT(l) == 0)
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return l;
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l1 = l;
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l2 = l;
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for(;;) {
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l2 = l2->next;
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l2 = NEXT(l2);
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if(l2 == 0)
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break;
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l2 = l2->next;
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l2 = NEXT(l2);
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if(l2 == 0)
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break;
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l1 = l1->next;
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l1 = NEXT(l1);
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}
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l2 = l1->next;
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l1->next = 0;
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l1 = datsort(l);
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l2 = datsort(l2);
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l2 = NEXT(l1);
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NEXT(l1) = 0;
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l1 = listsort(l, cmp, off);
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l2 = listsort(l2, cmp, off);
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/* set up lead element */
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if(datcmp(l1, l2) < 0) {
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if(cmp(l1, l2) < 0) {
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l = l1;
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l1 = l1->next;
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l1 = NEXT(l1);
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} else {
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l = l2;
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l2 = l2->next;
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l2 = NEXT(l2);
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}
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le = l;
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for(;;) {
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if(l1 == 0) {
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while(l2) {
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le->next = l2;
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NEXT(le) = l2;
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le = l2;
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l2 = l2->next;
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l2 = NEXT(l2);
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}
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le->next = 0;
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NEXT(le) = 0;
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break;
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}
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if(l2 == 0) {
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while(l1) {
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le->next = l1;
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NEXT(le) = l1;
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le = l1;
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l1 = l1->next;
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l1 = NEXT(l1);
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}
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break;
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}
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if(datcmp(l1, l2) < 0) {
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le->next = l1;
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if(cmp(l1, l2) < 0) {
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NEXT(le) = l1;
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le = l1;
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l1 = l1->next;
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l1 = NEXT(l1);
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} else {
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le->next = l2;
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NEXT(le) = l2;
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le = l2;
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l2 = l2->next;
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l2 = NEXT(l2);
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}
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}
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le->next = 0;
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NEXT(le) = 0;
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return l;
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#undef NEXT
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}
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Reloc*
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@ -1010,7 +1013,7 @@ dodata(void)
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s->type = SDATARELRO;
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}
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}
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datap = datsort(datap);
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datap = listsort(datap, datcmp, offsetof(Sym, next));
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/*
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* allocate sections. list is sorted by type,
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@ -311,6 +311,16 @@ static int map(ElfObj*, ElfSect*);
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static int readsym(ElfObj*, int i, ElfSym*, int);
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static int reltype(char*, int, uchar*);
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int
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valuecmp(Sym *a, Sym *b)
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{
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if(a->value < b->value)
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return -1;
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if(a->value > b->value)
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return +1;
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return 0;
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}
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void
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ldelf(Biobuf *f, char *pkg, int64 len, char *pn)
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{
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@ -541,13 +551,6 @@ ldelf(Biobuf *f, char *pkg, int64 len, char *pn)
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}
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s->size = sect->size;
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s->align = sect->align;
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if(s->type == STEXT) {
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if(etextp)
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etextp->next = s;
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else
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textp = s;
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etextp = s;
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}
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sect->sym = s;
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}
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@ -583,6 +586,12 @@ ldelf(Biobuf *f, char *pkg, int64 len, char *pn)
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continue;
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}
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s = sym.sym;
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if(s->outer != S) {
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if(s->dupok)
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continue;
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diag("%s: duplicate symbol reference: %s in both %s and %s", pn, s->name, s->outer->name, sect->sym->name);
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errorexit();
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}
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s->sub = sect->sym->sub;
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sect->sym->sub = s;
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s->type = sect->sym->type | (s->type&~SMASK) | SSUB;
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@ -611,7 +620,25 @@ ldelf(Biobuf *f, char *pkg, int64 len, char *pn)
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p->link = nil;
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p->pc = pc++;
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s->text = p;
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}
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}
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}
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// Sort outer lists by address, adding to textp.
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// This keeps textp in increasing address order.
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for(i=0; i<obj->nsect; i++) {
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s = obj->sect[i].sym;
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if(s == S)
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continue;
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if(s->sub)
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s->sub = listsort(s->sub, valuecmp, offsetof(Sym, sub));
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if(s->type == STEXT) {
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if(etextp)
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etextp->next = s;
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else
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textp = s;
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etextp = s;
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for(s = s->sub; s != S; s = s->sub) {
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etextp->next = s;
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etextp = s;
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}
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@ -792,7 +819,7 @@ readsym(ElfObj *obj, int i, ElfSym *sym, int needSym)
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// set dupok generally. See http://codereview.appspot.com/5823055/
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// comment #5 for details.
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if(s && sym->other == 2) {
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s->type = SHIDDEN;
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s->type |= SHIDDEN;
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s->dupok = 1;
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}
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}
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@ -804,14 +831,14 @@ readsym(ElfObj *obj, int i, ElfSym *sym, int needSym)
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// and should only reference by its index, not name, so we
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// don't bother to add them into hash table
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s = newsym(sym->name, version);
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s->type = SHIDDEN;
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s->type |= SHIDDEN;
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}
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break;
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case ElfSymBindWeak:
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if(needSym) {
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s = newsym(sym->name, 0);
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if(sym->other == 2)
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s->type = SHIDDEN;
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s->type |= SHIDDEN;
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}
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break;
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default:
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@ -593,13 +593,6 @@ ldmacho(Biobuf *f, char *pkg, int64 len, char *pn)
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} else
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s->type = SDATA;
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}
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if(s->type == STEXT) {
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if(etextp)
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etextp->next = s;
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else
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textp = s;
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etextp = s;
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}
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sect->sym = s;
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}
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@ -631,6 +624,12 @@ ldmacho(Biobuf *f, char *pkg, int64 len, char *pn)
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werrstr("reference to invalid section %s/%s", sect->segname, sect->name);
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continue;
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}
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if(s->outer != S) {
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if(s->dupok)
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continue;
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diag("%s: duplicate symbol reference: %s in both %s and %s", pn, s->name, s->outer->name, sect->sym->name);
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errorexit();
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}
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s->type = outer->type | SSUB;
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s->sub = outer->sub;
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outer->sub = s;
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@ -661,13 +660,31 @@ ldmacho(Biobuf *f, char *pkg, int64 len, char *pn)
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p->link = nil;
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p->pc = pc++;
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s->text = p;
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etextp->next = s;
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etextp = s;
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}
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sym->sym = s;
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}
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// Sort outer lists by address, adding to textp.
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// This keeps textp in increasing address order.
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for(i=0; i<c->seg.nsect; i++) {
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sect = &c->seg.sect[i];
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if((s = sect->sym) == S)
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continue;
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if(s->sub)
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s->sub = listsort(s->sub, valuecmp, offsetof(Sym, sub));
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if(s->type == STEXT) {
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if(etextp)
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etextp->next = s;
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else
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textp = s;
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etextp = s;
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for(s = s->sub; s != S; s = s->sub) {
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etextp->next = s;
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etextp = s;
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}
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}
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}
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// load relocations
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for(i=0; i<c->seg.nsect; i++) {
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sect = &c->seg.sect[i];
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@ -236,13 +236,6 @@ ldpe(Biobuf *f, char *pkg, int64 len, char *pn)
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s->p = sect->base;
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s->np = sect->size;
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s->size = sect->size;
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if(s->type == STEXT) {
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if(etextp)
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etextp->next = s;
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else
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textp = s;
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etextp = s;
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}
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sect->sym = s;
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if(strcmp(sect->name, ".rsrc") == 0)
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setpersrc(sect->sym);
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@ -327,6 +320,12 @@ ldpe(Biobuf *f, char *pkg, int64 len, char *pn)
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goto bad;
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s = sym->sym;
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if(s->outer != S) {
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if(s->dupok)
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continue;
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diag("%s: duplicate symbol reference: %s in both %s and %s", pn, s->name, s->outer->name, sect->sym->name);
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errorexit();
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}
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if(sym->sectnum == 0) {// extern
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if(s->type == SDYNIMPORT)
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s->plt = -2; // flag for dynimport in PE object files.
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@ -367,9 +366,27 @@ ldpe(Biobuf *f, char *pkg, int64 len, char *pn)
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p->link = nil;
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p->pc = pc++;
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s->text = p;
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etextp->next = s;
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}
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}
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// Sort outer lists by address, adding to textp.
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// This keeps textp in increasing address order.
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for(i=0; i<obj->nsect; i++) {
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s = obj->sect[i].sym;
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if(s == S)
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continue;
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if(s->sub)
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s->sub = listsort(s->sub, valuecmp, offsetof(Sym, sub));
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if(s->type == STEXT) {
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if(etextp)
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etextp->next = s;
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else
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textp = s;
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etextp = s;
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for(s = s->sub; s != S; s = s->sub) {
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etextp->next = s;
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etextp = s;
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}
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}
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}
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@ -196,7 +196,6 @@ void deadcode(void);
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Reloc* addrel(Sym*);
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void codeblk(int32, int32);
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void datblk(int32, int32);
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Sym* datsort(Sym*);
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void reloc(void);
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void relocsym(Sym*);
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void savedata(Sym*, Prog*, char*);
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@ -238,6 +237,8 @@ void setpersrc(Sym*);
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void doversion(void);
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void usage(void);
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void setinterp(char*);
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Sym* listsort(Sym*, int(*cmp)(Sym*, Sym*), int);
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int valuecmp(Sym*, Sym*);
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int pathchar(void);
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void* mal(uint32);
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@ -195,12 +195,13 @@ static int32 nfname;
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static uint32 funcinit;
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static Lock funclock;
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static uintptr lastvalue;
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static void
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dofunc(Sym *sym)
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{
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Func *f;
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switch(sym->symtype) {
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case 't':
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case 'T':
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@ -208,6 +209,11 @@ dofunc(Sym *sym)
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case 'L':
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if(runtime·strcmp(sym->name, (byte*)"etext") == 0)
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break;
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if(sym->value < lastvalue) {
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runtime·printf("symbols out of order: %p before %p\n", lastvalue, sym->value);
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runtime·throw("malformed symbol table");
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}
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lastvalue = sym->value;
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if(func == nil) {
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nfunc++;
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break;
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@ -544,6 +550,7 @@ buildfuncs(void)
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// count funcs, fnames
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nfunc = 0;
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nfname = 0;
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lastvalue = 0;
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walksymtab(dofunc);
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// Initialize tables.
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@ -553,6 +560,7 @@ buildfuncs(void)
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func[nfunc].entry = (uint64)etext;
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fname = runtime·mallocgc(nfname*sizeof fname[0], FlagNoPointers, 0, 1);
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nfunc = 0;
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lastvalue = 0;
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walksymtab(dofunc);
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// split pc/ln table by func
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