1#include <stddef.h> 2#include "dynlink.h" 3 4#ifndef START 5#define START "_dlstart" 6#endif 7 8#define SHARED 9 10#include "crt_arch.h" 11 12#ifndef GETFUNCSYM 13#define GETFUNCSYM(fp, sym, got) do { \ 14 __attribute__((__visibility__("hidden"))) void sym(); \ 15 static void (*static_func_ptr)() = sym; \ 16 __asm__ __volatile__ ( "" : "+m"(static_func_ptr) : : "memory"); \ 17 *(fp) = static_func_ptr; } while(0) 18#endif 19 20__attribute__((__visibility__("hidden"))) 21void _dlstart_c(size_t *sp, size_t *dynv) 22{ 23 size_t i, aux[AUX_CNT], dyn[DYN_CNT]; 24 size_t *rel, rel_size, base; 25 26 int argc = *sp; 27 char **argv = (void *)(sp+1); 28 29 for (i=argc+1; argv[i]; i++); 30 size_t *auxv = (void *)(argv+i+1); 31 32 for (i=0; i<AUX_CNT; i++) aux[i] = 0; 33 for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) 34 aux[auxv[i]] = auxv[i+1]; 35 36#if DL_FDPIC 37 struct fdpic_loadseg *segs, fakeseg; 38 size_t j; 39 if (dynv) { 40 /* crt_arch.h entry point asm is responsible for reserving 41 * space and moving the extra fdpic arguments to the stack 42 * vector where they are easily accessible from C. */ 43 segs = ((struct fdpic_loadmap *)(sp[-1] ? sp[-1] : sp[-2]))->segs; 44 } else { 45 /* If dynv is null, the entry point was started from loader 46 * that is not fdpic-aware. We can assume normal fixed- 47 * displacement ELF loading was performed, but when ldso was 48 * run as a command, finding the Ehdr is a heursitic: we 49 * have to assume Phdrs start in the first 4k of the file. */ 50 base = aux[AT_BASE]; 51 if (!base) base = aux[AT_PHDR] & -4096; 52 segs = &fakeseg; 53 segs[0].addr = base; 54 segs[0].p_vaddr = 0; 55 segs[0].p_memsz = -1; 56 Ehdr *eh = (void *)base; 57 Phdr *ph = (void *)(base + eh->e_phoff); 58 size_t phnum = eh->e_phnum; 59 size_t phent = eh->e_phentsize; 60 while (phnum-- && ph->p_type != PT_DYNAMIC) 61 ph = (void *)((size_t)ph + phent); 62 dynv = (void *)(base + ph->p_vaddr); 63 } 64#endif 65 66 for (i=0; i<DYN_CNT; i++) dyn[i] = 0; 67 for (i=0; dynv[i]; i+=2) if (dynv[i]<DYN_CNT) 68 dyn[dynv[i]] = dynv[i+1]; 69 70#if DL_FDPIC 71 for (i=0; i<DYN_CNT; i++) { 72 if (i==DT_RELASZ || i==DT_RELSZ) continue; 73 if (!dyn[i]) continue; 74 for (j=0; dyn[i]-segs[j].p_vaddr >= segs[j].p_memsz; j++); 75 dyn[i] += segs[j].addr - segs[j].p_vaddr; 76 } 77 base = 0; 78 79 const Sym *syms = (void *)dyn[DT_SYMTAB]; 80 81 rel = (void *)dyn[DT_RELA]; 82 rel_size = dyn[DT_RELASZ]; 83 for (; rel_size; rel+=3, rel_size-=3*sizeof(size_t)) { 84 if (!IS_RELATIVE(rel[1], syms)) continue; 85 for (j=0; rel[0]-segs[j].p_vaddr >= segs[j].p_memsz; j++); 86 size_t *rel_addr = (void *) 87 (rel[0] + segs[j].addr - segs[j].p_vaddr); 88 if (R_TYPE(rel[1]) == REL_FUNCDESC_VAL) { 89 *rel_addr += segs[rel_addr[1]].addr 90 - segs[rel_addr[1]].p_vaddr 91 + syms[R_SYM(rel[1])].st_value; 92 rel_addr[1] = dyn[DT_PLTGOT]; 93 } else { 94 size_t val = syms[R_SYM(rel[1])].st_value; 95 for (j=0; val-segs[j].p_vaddr >= segs[j].p_memsz; j++); 96 *rel_addr = rel[2] + segs[j].addr - segs[j].p_vaddr + val; 97 } 98 } 99#else 100 /* If the dynamic linker is invoked as a command, its load 101 * address is not available in the aux vector. Instead, compute 102 * the load address as the difference between &_DYNAMIC and the 103 * virtual address in the PT_DYNAMIC program header. */ 104 base = aux[AT_BASE]; 105 if (!base) { 106 size_t phnum = aux[AT_PHNUM]; 107 size_t phentsize = aux[AT_PHENT]; 108 Phdr *ph = (void *)aux[AT_PHDR]; 109 for (i=phnum; i--; ph = (void *)((char *)ph + phentsize)) { 110 if (ph->p_type == PT_DYNAMIC) { 111 base = (size_t)dynv - ph->p_vaddr; 112 break; 113 } 114 } 115 } 116 117 /* MIPS uses an ugly packed form for GOT relocations. Since we 118 * can't make function calls yet and the code is tiny anyway, 119 * it's simply inlined here. */ 120 if (NEED_MIPS_GOT_RELOCS) { 121 size_t local_cnt = 0; 122 size_t *got = (void *)(base + dyn[DT_PLTGOT]); 123 for (i=0; dynv[i]; i+=2) if (dynv[i]==DT_MIPS_LOCAL_GOTNO) 124 local_cnt = dynv[i+1]; 125 for (i=0; i<local_cnt; i++) got[i] += base; 126 } 127 128 rel = (void *)(base+dyn[DT_REL]); 129 rel_size = dyn[DT_RELSZ]; 130 for (; rel_size; rel+=2, rel_size-=2*sizeof(size_t)) { 131 if (!IS_RELATIVE(rel[1], 0)) continue; 132 size_t *rel_addr = (void *)(base + rel[0]); 133 *rel_addr += base; 134 } 135 136 rel = (void *)(base+dyn[DT_RELA]); 137 rel_size = dyn[DT_RELASZ]; 138 for (; rel_size; rel+=3, rel_size-=3*sizeof(size_t)) { 139 if (!IS_RELATIVE(rel[1], 0)) continue; 140 size_t *rel_addr = (void *)(base + rel[0]); 141 *rel_addr = base + rel[2]; 142 } 143#endif 144 145 stage2_func dls2; 146 GETFUNCSYM(&dls2, __dls2, base+dyn[DT_PLTGOT]); 147 dls2((void *)base, sp); 148} 149