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#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <dlfcn.h>
#include <linux/elf.h>
#include "_dl_int.h"
struct _dl_handle dl_test;
#define _ELF_DWN_ROUND(ps,n) ((n)&(~((ps)-1)))
#define _ELF_UP_ROUND(ps,n) ((((n)&((ps)-1))?(ps):0)+ _ELF_DWN_ROUND((ps),(n)))
#define _ELF_RST_ROUND(ps,n) ((n)&((ps)-1))
void _dl_jump();
/*
* this file is a Q. & D. hack ... don't think this is bug free or meaningfull
*/
static void *do_map_in(void *base, unsigned long length, int flags, int fd, unsigned long offset)
{
int perm = 0;
if (flags & PF_X) perm|=PROT_EXEC;
if (flags & PF_R) perm|=PROT_READ;
if (flags & PF_W) perm|=PROT_WRITE;
return mmap(base, length, perm, MAP_PRIVATE|((base)?MAP_FIXED:0), fd, offset);
}
unsigned long do_rel(struct _dl_handle * tmp_dl, unsigned long off)
{
// struct _dl_handle * tmp_dl = ((void*)*((&off)-1));
Elf32_Rel *tmp = ((void*)tmp_dl->plt_rel)+off;
int sym=ELF32_R_SYM(tmp->r_info);
register unsigned long sym_val;
printf("do_rel %08x %08x\n",tmp_dl,off);
printf ("do_rel %08x+%x\n",tmp_dl->plt_rel,off);
printf("do_rel @ %08x with type %d -> %d\n",tmp->r_offset,ELF32_R_TYPE(tmp->r_info),sym);
printf("do_rel sym %08x\n",tmp_dl->dyn_sym_tab[sym].st_value);
/* modify GOT for REAL symbol */
sym_val=((unsigned long)(tmp_dl->mem_base+tmp_dl->dyn_sym_tab[sym].st_value));
*((unsigned long*)(tmp_dl->mem_base+tmp->r_offset))=sym_val;
printf("do_rel sym %08x\n",sym_val);
/* HOWTO JUMP ?!? */
return sym_val;
}
void *_dl_open(const char*pathname, int fd, int flag)
{
int ps=getpagesize();
int i;
unsigned char buf[1024];
char *m=0,*d;
struct _dl_handle *ret=0;
unsigned long l;
Elf32_Ehdr *eh;
Elf32_Phdr *ph;
int ld_nr=0;
Elf32_Phdr *ld[4]={0,0,0,0};
Elf32_Phdr *dyn=0;
if (fd==-1) return 0;
printf("_dl_open: %s\n",pathname);
read(fd, buf, 1024);
eh=(Elf32_Ehdr*)buf;
ph=(Elf32_Phdr*)&buf[eh->e_phoff];
for (i=0; i<eh->e_phnum; i++) {
if (ph[i].p_type==PT_LOAD) {
ld[ld_nr++]=ph+i;
}
if (ph[i].p_type==PT_DYNAMIC) {
dyn=ph+i;
}
}
if (ld_nr==1) {
unsigned long offset = _ELF_DWN_ROUND(ps,ld[0]->p_offset);
unsigned long off = _ELF_RST_ROUND(ps,ld[0]->p_offset);
unsigned long length = _ELF_UP_ROUND(ps,ld[0]->p_memsz+off);
m = (char*)do_map_in(0, length, ld[0]->p_flags, fd, offset);
/* zero pad bss */
l = ld[0]->p_offset+ld[0]->p_filesz;
memset(m+l,0,length-l);
dl_test.mem_base=m;
dl_test.mem_size=length;
dl_test.lnk_count=0;
ret = &dl_test;
}
else if (ld_nr==2) { /* aem... yes Quick & Really Dirty / for the avarage 99% */
//unsigned long text_addr = _ELF_DWN_ROUND(ps,ld[0]->p_vaddr);
unsigned long text_offset = _ELF_DWN_ROUND(ps,ld[0]->p_offset);
unsigned long text_off = _ELF_RST_ROUND(ps,ld[0]->p_offset);
unsigned long text_size = _ELF_UP_ROUND(ps,ld[0]->p_memsz+text_off);
unsigned long data_addr = _ELF_DWN_ROUND(ps,ld[1]->p_vaddr);
unsigned long data_offset = _ELF_DWN_ROUND(ps,ld[1]->p_offset);
unsigned long data_off = _ELF_RST_ROUND(ps,ld[1]->p_offset);
unsigned long data_size = _ELF_UP_ROUND(ps,ld[1]->p_memsz+data_off);
unsigned long data_fsize = _ELF_UP_ROUND(ps,ld[1]->p_filesz+data_off);
/* mmap all mem_blocks for *.so */
l = text_size+data_size;
dl_test.mem_size=l;
m = (char*) do_map_in(0,l,ld[0]->p_flags,fd,text_offset);
/* release data,bss part */
mprotect(m+data_addr, data_size, PROT_NONE);
/* mmap data,bss part */
d = (char*) do_map_in(m+data_addr,data_fsize,ld[1]->p_flags,fd,data_offset);
/* zero pad bss */
l = data_off+ld[1]->p_filesz;
memset(d+l,0,data_size-l);
/* more bss ? */
if (data_size>data_fsize) {
l = data_size-data_fsize;
mmap(d+data_fsize, l, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0);
}
dl_test.mem_base=m;
dl_test.lnk_count=0;
ret = &dl_test;
}
printf("_dl_open pre resolv\n");
if (ret) {
Elf32_Dyn* dyn_tab = (void*)m+dyn->p_vaddr;
void (*init)();
unsigned long* got=0;
void* jmprel=0;
int pltreltype=0;
int pltrelsize=0;
printf("_dl_open IN resolv\n");
for(i=0;dyn_tab[i].d_tag;i++) {
if (dyn_tab[i].d_tag==DT_HASH) {
ret->hash_tab = (unsigned long*)(m+dyn_tab[i].d_un.d_ptr);
}
if (dyn_tab[i].d_tag==DT_SYMTAB) {
ret->dyn_sym_tab = (Elf32_Sym*)(m+dyn_tab[i].d_un.d_ptr);
}
if (dyn_tab[i].d_tag==DT_STRTAB) {
ret->dyn_str_tab = (char*)(m+dyn_tab[i].d_un.d_ptr);
}
if (dyn_tab[i].d_tag==DT_FINI) {
ret->fini = (void(*)(void))(m+dyn_tab[i].d_un.d_val);
}
if (dyn_tab[i].d_tag==DT_INIT) {
init = (void(*)(void))(m+dyn_tab[i].d_un.d_val);
printf("init @ %08x\n",init);
}
if (dyn_tab[i].d_tag==DT_PLTGOT) {
got=(unsigned long*)(m+dyn_tab[i].d_un.d_val);
}
if (dyn_tab[i].d_tag==DT_PLTREL) {
pltreltype=dyn_tab[i].d_un.d_val;
}
if (dyn_tab[i].d_tag==DT_PLTRELSZ) {
pltrelsize=dyn_tab[i].d_un.d_val;
}
if (dyn_tab[i].d_tag==DT_JMPREL) {
jmprel=(m+dyn_tab[i].d_un.d_val);
dl_test.plt_rel=jmprel;
}
}
/* GOT */
got[0]+=(unsigned long)m;
got[1]=(unsigned long)&dl_test;
// got[2]=(unsigned long)do_rel;
got[2]=(unsigned long)(_dl_jump);
/* */
if (pltreltype == DT_REL) {
Elf32_Rel *tmp = jmprel;
for (;(char*)tmp<(((char*)jmprel)+pltrelsize);(char*)tmp=((char*)tmp)+sizeof(Elf32_Rel)) {
*((unsigned long*)(m+tmp->r_offset))+=(unsigned long)m;
// *((unsigned long*)(m+tmp->r_offset))+=(unsigned long)do_rel;
printf("rel @ %08x with type %d -> %d\n",tmp->r_offset,ELF32_R_TYPE(tmp->r_info),ELF32_R_SYM(tmp->r_info));
}
}
printf("_dl_open post resolv, pre init\n");
init();
}
printf("_dl_open post resolv, init\n");
close(fd);
return ret;
}
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