ref: c04f70e2bb4a02655bb8a6247a8f07f75ff431bd
dir: /libdynld/dynld.c/
#include "lib9.h" #include <a.out.h> #include <dynld.h> static ulong get2(uchar *b) { return (b[0] << 8) | b[1]; } static ulong get4(uchar *b) { return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3]; } static ulong lgetbe(ulong l) { union { ulong l; uchar c[4]; } u; u.l = l; return get4(u.c); } Dynsym* dynfindsym(char *s, Dynsym *tab, int ntab) { int n, n2, d; Dynsym *t, *m; t = tab; n = ntab; while(n > 0){ n2 = n>>1; m = t+n2; d = strcmp(s, m->name); if(d < 0){ n = n2; continue; } if(d > 0){ t = m+1; n -= n2+1; continue; } return m; } return nil; } void* dynimport(Dynobj *o, char *name, ulong sig) { Dynsym *t; t = dynfindsym(name, o->export, o->nexport); if(t == nil || sig != 0 && t->sig != 0 && t->sig != sig) return nil; return (void*)t->addr; } int dyntabsize(Dynsym *t) { int n; for(n = 0; t->name != nil; t++) n++; return n; } void dynobjfree(Dynobj *o) { if(o != nil){ free(o->base); free(o->import); free(o); } } void dynfreeimport(Dynobj *o) { free(o->import); o->import = nil; o->nimport = 0; } static char Ereloc[] = "error reading object file"; Dynobj* dynloadgen(void *file, long (*rd)(void*,void*,long), vlong (*sk)(void*,vlong,int), void (*werr)(char*), Dynsym *tab, int ntab, ulong maxsize) { int i, m, n, ni, nr, relsize; ulong syms, entry, sig, p, a; uchar *base; Exec e; Dynsym *t; Dynobj *l; char *s, *err, buf[64]; uchar *reldata, *rp, *ep; vlong off; err = Ereloc; /* default */ off = (*sk)(file, 0, 1); l = mallocz(sizeof(Dynobj), 1); if(l == nil){ err = "can't allocate Dynobj"; goto Error; } if((*rd)(file, &e, sizeof(Exec)) != sizeof(Exec)) goto Error; if(lgetbe(e.magic) != dynmagic()){ err = "not dynamic object file or wrong platform"; goto Error; } l->text = lgetbe(e.text); l->data = lgetbe(e.data); l->bss = lgetbe(e.bss); syms = lgetbe(e.syms)+lgetbe(e.spsz)+lgetbe(e.pcsz); entry = lgetbe(e.entry); l->size = l->text + l->data + l->bss; if(entry < 0 || entry >= l->size || entry & 3){ err = "invalid export table pointer (entry point)"; goto Error; } if(maxsize && l->size >= maxsize){ snprint(buf, sizeof(buf), "%lud: object too big", l->size); err = buf; goto Error; } l->base = base = malloc(l->size); if(base == nil){ err = "out of memory: loading object file"; goto Error; } l->export = (Dynsym*)(base+entry); if((*rd)(file, base, l->text+l->data) != l->text+l->data) goto Error; memset(base+l->text+l->data, 0, l->bss); if((*sk)(file, syms, 1) < 0) goto Error; if((*rd)(file, buf, 4) != 4) goto Error; relsize = get4((uchar*)buf); /* always contains at least an import count (might be zero) */ if(relsize < 4) goto Error; reldata = malloc(relsize); if(reldata == nil){ err = "out of memory: relocation data"; goto Error; } if((*rd)(file, reldata, relsize) != relsize) goto Error; rp = reldata; ep = reldata+relsize; ni = get4(rp); rp += 4; if(ni < 0 || ni > 8000) goto Error; /* implausible size */ l->nimport = ni; l->import = malloc(ni*sizeof(Dynsym*)); if(l->import == nil){ err = "out of memory: symbol table"; goto Error; } for(i = 0; i < ni; i++){ if(rp+5 > ep) goto Error; sig = get4(rp); rp += 4; s = (char*)rp; while(*rp++) if(rp >= ep) goto Error; t = dynfindsym(s, tab, ntab); if(t == nil){ snprint(buf, sizeof(buf), "undefined symbol: %s", s); err = buf; goto Error; } if(sig != 0 && t->sig != 0 && t->sig != sig){ snprint(buf, sizeof(buf), "signature mismatch: %s (%lux != %lux)", s, sig, t->sig); err = buf; goto Error; } l->import[i] = t; } a = 0; if(rp+4 > ep) goto Error; nr = get4(rp); rp += 4; for(i = 0; i < nr; i++){ if(rp >= ep) goto Error; m = *rp++; n = m>>6; if(rp+(1<<n) > ep) goto Error; switch(n){ case 0: p = *rp++; break; case 1: p = get2(rp); rp += 2; break; case 2: p = get4(rp); rp += 4; break; default: goto Error; } a += p; err = dynreloc(base, a, m&0xf, l->import, ni); if(err != nil){ snprint(buf, sizeof(buf), "dynamic object: %s", err); err = buf; goto Error; } } free(reldata); /* could check relocated export table here */ l->nexport = dyntabsize(l->export); segflush(base, l->text); return l; Error: if(off >= 0) (*sk)(file, off, 0); /* restore original file offset */ (*werr)(err); dynobjfree(l); return nil; } int dynloadable(void* file, long (*rd)(void*,void*,long), vlong (*sk)(void*,vlong,int)) { long magic; if((*rd)(file, &magic, sizeof(magic)) != sizeof(magic)){ (*sk)(file, -(signed int)sizeof(magic), 1); return 0; } (*sk)(file, -(signed int)sizeof(magic), 1); return lgetbe(magic) == dynmagic(); }