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