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