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