source: asp3_tinet_ecnl_arm/trunk/musl-1.1.18/ldso/dlstart.~c@ 352

#include <stddef.h>
#include "dynlink.h"

#ifndef START
#define START "_dlstart"
#endif

#define SHARED

#include "crt_arch.h"

#ifndef GETFUNCSYM
#define GETFUNCSYM(fp, sym, got) do { \
        __attribute__((__visibility__("hidden"))) void sym(); \
        static void (*static_func_ptr)() = sym; \
        __asm__ __volatile__ ( "" : "+m"(static_func_ptr) : : "memory"); \
        *(fp) = static_func_ptr; } while(0)
#endif

__attribute__((__visibility__("hidden")))
void _dlstart_c(size_t *sp, size_t *dynv)
{
        size_t i, aux[AUX_CNT], dyn[DYN_CNT];
        size_t *rel, rel_size, base;

        int argc = *sp;
        char **argv = (void *)(sp+1);

        for (i=argc+1; argv[i]; i++);
        size_t *auxv = (void *)(argv+i+1);

        for (i=0; i<AUX_CNT; i++) aux[i] = 0;
        for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT)
                aux[auxv[i]] = auxv[i+1];

#if DL_FDPIC
        struct fdpic_loadseg *segs, fakeseg;
        size_t j;
        if (dynv) {
                /* crt_arch.h entry point asm is responsible for reserving
                 * space and moving the extra fdpic arguments to the stack
                 * vector where they are easily accessible from C. */
                segs = ((struct fdpic_loadmap *)(sp[-1] ? sp[-1] : sp[-2]))->segs;
        } else {
                /* If dynv is null, the entry point was started from loader
                 * that is not fdpic-aware. We can assume normal fixed-
                 * displacement ELF loading was performed, but when ldso was
                 * run as a command, finding the Ehdr is a heursitic: we
                 * have to assume Phdrs start in the first 4k of the file. */
                base = aux[AT_BASE];
                if (!base) base = aux[AT_PHDR] & -4096;
                segs = &fakeseg;
                segs[0].addr = base;
                segs[0].p_vaddr = 0;
                segs[0].p_memsz = -1;
                Ehdr *eh = (void *)base;
                Phdr *ph = (void *)(base + eh->e_phoff);
                size_t phnum = eh->e_phnum;
                size_t phent = eh->e_phentsize;
                while (phnum-- && ph->p_type != PT_DYNAMIC)
                        ph = (void *)((size_t)ph + phent);
                dynv = (void *)(base + ph->p_vaddr);
        }
#endif

        for (i=0; i<DYN_CNT; i++) dyn[i] = 0;
        for (i=0; dynv[i]; i+=2) if (dynv[i]<DYN_CNT)
                dyn[dynv[i]] = dynv[i+1];

#if DL_FDPIC
        for (i=0; i<DYN_CNT; i++) {
                if (i==DT_RELASZ || i==DT_RELSZ) continue;
                if (!dyn[i]) continue;
                for (j=0; dyn[i]-segs[j].p_vaddr >= segs[j].p_memsz; j++);
                dyn[i] += segs[j].addr - segs[j].p_vaddr;
        }
        base = 0;

        const Sym *syms = (void *)dyn[DT_SYMTAB];

        rel = (void *)dyn[DT_RELA];
        rel_size = dyn[DT_RELASZ];
        for (; rel_size; rel+=3, rel_size-=3*sizeof(size_t)) {
                if (!IS_RELATIVE(rel[1], syms)) continue;
                for (j=0; rel[0]-segs[j].p_vaddr >= segs[j].p_memsz; j++);
                size_t *rel_addr = (void *)
                        (rel[0] + segs[j].addr - segs[j].p_vaddr);
                if (R_TYPE(rel[1]) == REL_FUNCDESC_VAL) {
                        *rel_addr += segs[rel_addr[1]].addr
                                - segs[rel_addr[1]].p_vaddr
                                + syms[R_SYM(rel[1])].st_value;
                        rel_addr[1] = dyn[DT_PLTGOT];
                } else {
                        size_t val = syms[R_SYM(rel[1])].st_value;
                        for (j=0; val-segs[j].p_vaddr >= segs[j].p_memsz; j++);
                        *rel_addr = rel[2] + segs[j].addr - segs[j].p_vaddr + val;
                }
        }
#else
        /* If the dynamic linker is invoked as a command, its load
         * address is not available in the aux vector. Instead, compute
         * the load address as the difference between &_DYNAMIC and the
         * virtual address in the PT_DYNAMIC program header. */
        base = aux[AT_BASE];
        if (!base) {
                size_t phnum = aux[AT_PHNUM];
                size_t phentsize = aux[AT_PHENT];
                Phdr *ph = (void *)aux[AT_PHDR];
                for (i=phnum; i--; ph = (void *)((char *)ph + phentsize)) {
                        if (ph->p_type == PT_DYNAMIC) {
                                base = (size_t)dynv - ph->p_vaddr;
                                break;
                        }
                }
        }

        /* MIPS uses an ugly packed form for GOT relocations. Since we
         * can't make function calls yet and the code is tiny anyway,
         * it's simply inlined here. */
        if (NEED_MIPS_GOT_RELOCS) {
                size_t local_cnt = 0;
                size_t *got = (void *)(base + dyn[DT_PLTGOT]);
                for (i=0; dynv[i]; i+=2) if (dynv[i]==DT_MIPS_LOCAL_GOTNO)
                        local_cnt = dynv[i+1];
                for (i=0; i<local_cnt; i++) got[i] += base;
        }

        rel = (void *)(base+dyn[DT_REL]);
        rel_size = dyn[DT_RELSZ];
        for (; rel_size; rel+=2, rel_size-=2*sizeof(size_t)) {
                if (!IS_RELATIVE(rel[1], 0)) continue;
                size_t *rel_addr = (void *)(base + rel[0]);
                *rel_addr += base;
        }

        rel = (void *)(base+dyn[DT_RELA]);
        rel_size = dyn[DT_RELASZ];
        for (; rel_size; rel+=3, rel_size-=3*sizeof(size_t)) {
                if (!IS_RELATIVE(rel[1], 0)) continue;
                size_t *rel_addr = (void *)(base + rel[0]);
                *rel_addr = base + rel[2];
        }
#endif

        stage2_func dls2;
        GETFUNCSYM(&dls2, __dls2, base+dyn[DT_PLTGOT]);
        dls2((void *)base, sp);
}