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hello_world.c
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hello_world.c
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#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <unistd.h>
#define ALIGN 0x1
#define ELF32_ST_INFO(b,t) (((b)<<4)+((t)&0xf))
int main() {
char *o, *buf, *code, *entry, *je, *tje, *to, *phdr;
char *shstrtab_off, *strtab_off,*data_off, *text_off, *symtab_off;
unsigned int *shdr_off;
const int poolsz = 256 * 1024;
code = malloc(poolsz);
buf = malloc(poolsz);
o = buf = (char*)(((int)buf + 4096 -1) & -4096);
je = code;
char* code_hello_w = je; // movt r0, addr of helloworld
je +=4;
char* code_hello_t = je;; // movw r0, addr of helloworld
je +=4;
*(int*)je = 0xe3a01000; // mov r1, #0
je +=4;
*(int*)je = 0xe3a02000; // mov r2, #0
je +=4;
char* bl_printf_movw = je;
je +=4;
char* bl_printf_movt = je;
je +=4;
*(int*)je = 0xe28fe000; // add lr, pc ,#0
je +=4;
// *(int*)je = 0xe59cf000; // ldr pc, [ip]
*(int*)je = 0xe1a0f00c; // mov pc, ip
je +=4;
// XXX: rand() has no effect here
char* bl_rand_movw = je;
je +=4;
char* bl_rand_movt = je;
je +=4;
*(int*)je = 0xe28fe000; // add lr, pc ,#0
je +=4;
// *(int*)je = 0xe59cf000; // ldr pc, [ip]
*(int*)je = 0xe1a0f00c; // mov pc, ip
je +=4;
*(int*)je = 0xe3a00000; // mov r0, #0
je +=4;
*(int*)je = 0xe3a07001; // mov r7, #1
je +=4;
*(int*)je = 0xef000000; // svc 0
je +=4;
// elf header
*o++ = 0x7f; *o++ = 'E'; *o++ = 'L'; *o++ = 'F';
*o++ = 1; *o++ = 1; *o++ = 1; *o++ = 0;
o = o + 8;
*o++ = 2; *o++ = 0; *o++ = 40; *o++ = 0; // e_type 2 = executable & e_machine 40 = ARM
*(int*)o = 1; o = o + 4;
entry = o; o = o + 4; // e_entry
*(int*)o = 52; o = o + 4; // e_phoff
shdr_off = (unsigned int*)o; o = o + 4; // e_shoff
// *(int*)o = 0x2000; o = o + 4; // e_shoff
*(int*)o = 0x5000400; o = o + 4; // e_flags
*o++ = 52; *o++ = 0;
*o++ = 32; *o++ = 0; *o++ = 4; *o++ = 0; // e_phentsize & e_phnum
*o++ = 40; *o++ = 0; *o++ = 12; *o++ = 0; // e_shentsize & e_shnum
*o++ = 1; *o++ = 0;
phdr = o;
char* v_text_record, *s_text;
to = phdr;
// program header
// PT_LOAD for code
*(int*)to = 1; to = to + 4;
// offset
*(int*)to = ALIGN; to = to + 4;
v_text_record = to; to = to + 4;
*(int*)to = (int)to + 123 + 32 +24 + 32 - 4; to = to + 4;
s_text = to; to = to + 4;
*(int*)to = (je - code); to = to + 4;
*(int*)to = 5; to = to + 4;
*(int*)to = ALIGN; to = to + 4;
char* v_data_size;
// PT_LOAD for data
*(int*)to = 1; to = to + 4;
*(int*)to = 52 + 32 * 4; to = to + 4;
*(int*)to = (int)to + 24 + 32*2; to = to + 4;
*(int*)to = (int)to + 24 + 32*2 -4; to = to + 4;
v_data_size = to; to = to + 4;
*(int*)to = 0x8; to = to + 4;
*(int*)to = 6; to = to + 4;
*(int*)to = 0x8; to = to + 4;
// PT_INTERP
*(int*)to = 3; to = to + 4; *(int*)to = 52 + 32 * 4; to = to + 4;
*(int*)to = (int)to + 24 + 32; to = to + 4;
*(int*)to = (int)to + 24 + 32 - 4; to = to + 4;
*(int*)to = 25; to = to + 4;
*(int*)to = 25; to = to + 4;
*(int*)to = 4; to = to + 4; *(int*)to = 1; to = to + 4;
char* v_dym;
char* s_dym;
int dym_off = 52 + 32 *4 + 25;
// PT_DYNAMIC
*(int*)to = 2; to = to + 4; *(int*)to = dym_off; to = to + 4;
v_dym = to; to = to + 4;
*(int*)to = (int)to + 24 + 25 -4; to = to + 4;
s_dym = to; to = to + 4;
*(int*)to = 80; to = to + 4;
*(int*)to = 6; to = to + 4; *(int*)to = 4; to = to + 4;
char* _data = to;
memcpy(to, "/lib/ld-linux-armhf.so.3", 25);
to += 25;
*(int*)v_dym = (int)to;
*(int*)(v_dym + 4) = (int)to;
char* v_strtab, *v_symtab, *_v_rel, *_v_got, *__v_rel,*_v_symtab, *_v_plt;
char* s_strtab, *_s_rel, *__s_rel, *_s_plt,*_s_symtab;
int s_symtab;
// .dynamic
*(int*)to = 5; to = to + 4; v_strtab = to; to = to + 4;
*(int*)to = 10; to = to + 4; s_strtab = to; to = to + 4;
*(int*)to = 6; to = to + 4; _v_symtab = to; to = to + 4;
*(int*)to = 11; to = to + 4; *(int*)to = 16; to = to + 4;
*(int*)to = 1; to = to + 4; *(int*)to = 8; to = to + 4;
*(int*)to = 1; to = to + 4; *(int*)to = 18; to = to + 4;
*(int*)to = 17; to = to + 4; _v_rel = to; to = to + 4;
*(int*)to = 18; to = to + 4; _s_rel = to; to = to + 4;
*(int*)to = 19; to = to + 4; __s_rel = to; to = to + 4;
*(int*)to = 3; to = to + 4; _v_got = to; to = to + 4;
*(int*)to = 2; to = to + 4; *(int*)to = 16; to = to + 4;
*(int*)to = 20; to = to + 4; *(int*)to = 17; to = to + 4;
*(int*)to = 23; to = to + 4; __v_rel = to; to = to + 4;
*(int*)to = 0; to = to + 8;
// XXX
// Why we must add 16bytes to let readelf show the end of two entry?
*(int*)s_dym = ((int)to - *(int*)v_dym) + 16;
*(int*)(s_dym + 4) = *(int*)s_dym;
shstrtab_off = (char*)(to - buf);
char *shstrtab = "\0.text\0.data\0.bss\0.shstrtab\0.symtab\0.strtab\0"
".interp\0.dynamic\0.dynsym\0.dynstr\0.rel.plt\0.plt\0"
".got\0.rodata\0";
int shstrtab_size = 104;
memcpy(to, shstrtab, shstrtab_size);
to += shstrtab_size;
char* v_dynstr = to;
*(int*)v_strtab = (int)to;
char* dynstr_off = (char*)(to - buf);
char *dynstr = "\0printf\0libc.so.6\0libdl.so.2\0rand\0";
int dynstr_size = 35;
*(int*)s_strtab = dynstr_size;
memcpy(to, dynstr, dynstr_size);
to += dynstr_size;
char *dynsym_off = (char*)(to - buf);
char* v_dynsym;
int s_dynsym;
v_dynsym = to;
*(int*)_v_symtab = (int)to;
memset(to, 0, 16);
to += 16;
// .dynsym for printf
*(int*)to = 1; to = to + 4;
*(int*)to = 0; to = to + 4;
*(int*)to = 0; to = to + 4;
*to = ELF32_ST_INFO(1, 2); to = to + 1;
*to = 0; to++;
*to++ = 0; *to++ = 0;
// .dynsym for rand
*(int*)to = 29; to = to + 4;
*(int*)to = 0; to = to + 4;
*(int*)to = 0; to = to + 4;
*to = ELF32_ST_INFO(1, 2); to = to + 1;
*to = 0; to++;
*to++ = 0; *to++ = 0;
s_dynsym = (int)to - (int)v_dynsym;
// *(int*)_s_symtab = (int)to - (int)v_dynsym;
//-------------------------.got
char* v_got = to;
*(int*) _v_got = (int)to;
char* got_off = (char*)(to - buf);
*(int*)to = *(int*)v_dym; to = to + 4;
to += 4; // reserved 2 and 3 entry for linker
char* to_got_movw = to;
char* to_got_movt = to;
to += 4; // reserved 2 and 3 entry for linker
char* got_printf = to;
char * v_plt1 = to; to += 4;
char* _got_rand = to;
char * v_plt2 = to; to+=4;
to = to + 4; // end with 0x0
int got_size = (int)to - (int)v_got;
//-------------------------------------------.text
to = (char*)(((int)to + (ALIGN - 1)) & -ALIGN);
char *_text = to;
*(int*) v_text_record = (int)to;
*(int*) entry = (int)to;
*(int*) (v_text_record + 4) = (int)to;
*(int*) v_data_size = (int)_text - (int)_data;
*(int*) (v_data_size + 4) = (int)_text - (int)_data;
char *code_r = to;
text_off = (char*)(to - buf);
*(int*) (v_text_record - 4) = (int)text_off;
to += je - code;
//------------------------------.plt
char* v_plt = to;
*(int*) v_plt1 = (int)to;
*(int*) v_plt2 = (int)to;
char* plt_off = (char*)(to - buf);
*(int*)to = 0xe52de004; to = to + 4; // push {lr}
*(int*)to = 0xe300a000 | (0xfff & (int)(to_got_movw)) | (0xf0000 & ((int)(to_got_movw) << 4));
to = to + 4;
*(int*)to = 0xe340a000 | (0xfff & ((int)(to_got_movt)>>16)) | (0xf0000 & ((int)(to_got_movt) >> 12));
to = to + 4;
*(int*)to = 0xe1a0e00a; to = to + 4;// mov lr,r10
*(int*)to = 0xe59ef000; to = to + 4;// ldr pc, [lr]
// printf
*(int*)bl_printf_movw = 0xe300c000 | (0xfff & (int)(to)) | (0xf0000 & ((int)(to) << 4));
*(int*)bl_printf_movt = 0xe340c000 | (0xfff & ((int)(to)>>16)) | (0xf0000 & ((int)(to) >> 12));
*(int*) to = 0xe300c000 | (0xfff & (int)(got_printf)) | (0xf0000 & ((int)(got_printf) << 4));
to += 4;
*(int*) to = 0xe340c000 | (0xfff & ((int)(got_printf)>>16)) | (0xf0000 & ((int)(got_printf) >> 12));
to += 4;
*(int*)to = 0xe59cf000; to = to + 4;// ldr pc, [ip]
// rand
*(int*)bl_rand_movw = 0xe300c000 | (0xfff & (int)(to)) | (0xf0000 & ((int)(to) << 4));
*(int*)bl_rand_movt = 0xe340c000 | (0xfff & ((int)(to)>>16)) | (0xf0000 & ((int)(to) >> 12));
*(int*) to = 0xe300c000 | (0xfff & (int)(_got_rand)) | (0xf0000 & ((int)(_got_rand) << 4));
to += 4;
*(int*) to = 0xe340c000 | (0xfff & ((int)(_got_rand)>>16)) | (0xf0000 & ((int)(_got_rand) >> 12));
to += 4;
*(int*)to = 0xe59cf000; to = to + 4;// ldr pc, [ip]
int plt_size = (int)to - (int)v_plt;
//---------------------------------------.rel
char* v_rel = to;
*(int*) _v_rel = (int)to;
*(int*) __v_rel = (int)to;
char* rel_off = (char*)(to - buf);
*(int*)to = (int)got_printf; to = to + 4;
*(int*)to = 0x16 | 1 << 8 ; to = to + 4; // 0x16 R_ARM_JUMP_SLOT | .dymsyn index << 8
*(int*)to = (int)_got_rand; to = to + 4;
*(int*)to = 0x16 | 2 << 8 ; to = to + 4; // 0x16 R_ARM_JUMP_SLOT | .dymsyn index << 8
int rel_size = (int)to - (int)v_rel;
*(int*) _s_rel = rel_size;
*(int*) __s_rel = 8;
char* _rodata = "Hello world!!\n\0";
*(int*)code_hello_w = 0xe3000000 | (0xfff & (int)(to)) | (0xf0000 & ((int)(to) << 4));
*(int*)code_hello_t = 0xe3400000 | (0xfff & ((int)(to)>>16)) | (0xf0000 & ((int)(to) >> 12));
char* v_rodata = to;
char* rodata_off = (char*)(to - buf);
int rodata_size = 15;
memcpy(to, _rodata, rodata_size);
to += rodata_size;
*(int*) s_text = (int)to - (int)_text;
*(int*) (s_text + 4) = (int)to - (int)_text;
memcpy(code_r, code, je - code);
to = (char*)(((int)to + (ALIGN - 1)) & -ALIGN);
*shdr_off = (unsigned int)(to - buf);
// shdr
// index 0
*(int*)to = 0; to = to + 4; *(int*)to = 0; to = to + 4;
*(int*)to = 0; to = to + 4;
*(int*)to = 0; to = to + 4;
*(int*)to = 0; to = to + 4;
*(int*)to = 0; to = to + 4;
*(int*)to = 0; to = to + 4; *(int*)to = 0; to = to + 4;
*(int*)to = 0; to = to + 4; *(int*)to = 0; to = to + 4;
// .shstrtab 1
*(int*)to = 18; to = to + 4; *(int*)to = 3; to = to + 4;
*(int*)to = 0; to = to + 4;
*(int*)to = 0; to = to + 4;
*(int*)to = (int)shstrtab_off; to = to + 4;
*(int*)to = shstrtab_size; to = to + 4;
*(int*)to = 0; to = to + 4; *(int*)to = 0; to = to + 4;
*(int*)to = 1; to = to + 4; *(int*)to = 0; to = to + 4;
// .text 2
*(int*)to = 1; to = to + 4; *(int*)to = 1; to = to + 4;
*(int*)to = 6; to = to + 4;
*(int*)to = (int)_text; to = to + 4;
*(int*)to = (int)text_off; to = to + 4;
*(int*)to = je - code; to = to + 4;
*(int*)to = 0; to = to + 4; *(int*)to = 0; to = to + 4;
*(int*)to = 4; to = to + 4; *(int*)to = 0; to = to + 4;
// .data 3
*(int*)to = 7; to = to + 4; *(int*)to = 1; to = to + 4;
*(int*)to = 3; to = to + 4;
*(int*)to = (int)_data ; to = to + 4;
*(int*)to = 52 + 32 * 2; to = to + 4;
*(int*)to = *(int*)v_data_size; to = to + 4;
*(int*)to = 0; to = to + 4; *(int*)to = 0; to = to + 4;
*(int*)to = 4; to = to + 4; *(int*)to = 0; to = to + 4;
// .interp 4
*(int*)to = 44; to = to + 4; *(int*)to = 1; to = to + 4;
*(int*)to = 2; to = to + 4;
*(int*)to = (int)_data; to = to + 4;
*(int*)to = 52 + 32 * 4; to = to + 4;
*(int*)to = 25; to = to + 4;
*(int*)to = 0; to = to + 4; *(int*)to = 0; to = to + 4;
*(int*)to = 1; to = to + 4; *(int*)to = 0; to = to + 4;
// .dynamic 5
*(int*)to = 52; to = to + 4; *(int*)to = 6; to = to + 4;
*(int*)to = 3; to = to + 4;
*(int*)to = *(int*)v_dym; to = to + 4;
*(int*)to = dym_off; to = to + 4;
*(int*)to = *(int*)s_dym; to = to + 4;
*(int*)to = 7; to = to + 4; *(int*)to = 0; to = to + 4;
*(int*)to = 4; to = to + 4; *(int*)to = 0; to = to + 4;
// .dynsym 6
*(int*)to = 61; to = to + 4; *(int*)to = 11; to = to + 4;
*(int*)to = 2; to = to + 4;
*(int*)to = (int)v_dynsym; to = to + 4;
*(int*)to = (int)dynsym_off; to = to + 4;
*(int*)to = s_dynsym; to = to + 4;
*(int*)to = 7; to = to + 4; *(int*)to = 123; to = to + 4;
*(int*)to = 4; to = to + 4; *(int*)to = 16; to = to + 4;
// .dynstr 7
*(int*)to = 69; to = to + 4; *(int*)to = 3; to = to + 4;
*(int*)to = 2; to = to + 4;
*(int*)to = (int)v_dynstr; to = to + 4;
*(int*)to = (int)dynstr_off; to = to + 4;
*(int*)to = dynstr_size; to = to + 4;
*(int*)to = 0; to = to + 4; *(int*)to = 0; to = to + 4;
*(int*)to = 1; to = to + 4; *(int*)to = 0; to = to + 4;
// .rel.plt 8
*(int*)to = 77; to = to + 4; *(int*)to = 9; to = to + 4;
*(int*)to = 2 | 0x40 ; to = to + 4;
*(int*)to = (int)v_rel; to = to + 4;
*(int*)to = (int)rel_off; to = to + 4;
*(int*)to = rel_size; to = to + 4;
*(int*)to = 6; to = to + 4; *(int*)to = 9; to = to + 4;
*(int*)to = 4; to = to + 4; *(int*)to = 0x8; to = to + 4;
// .plt 9
*(int*)to = 86; to = to + 4; *(int*)to = 1; to = to + 4;
*(int*)to = 6; to = to + 4;
*(int*)to = (int)v_plt; to = to + 4;
*(int*)to = (int)plt_off; to = to + 4;
*(int*)to = plt_size; to = to + 4;
*(int*)to = 0; to = to + 4; *(int*)to = 0; to = to + 4;
*(int*)to = 4; to = to + 4; *(int*)to = 4; to = to + 4;
// .got 10
*(int*)to = 91; to = to + 4; *(int*)to = 1; to = to + 4;
*(int*)to = 3; to = to + 4;
*(int*)to = (int)v_got; to = to + 4;
*(int*)to = (int)got_off; to = to + 4;
*(int*)to = got_size; to = to + 4;
*(int*)to = 0; to = to + 4; *(int*)to = 0; to = to + 4;
*(int*)to = 4; to = to + 4; *(int*)to = 4; to = to + 4;
// .rodata 11
*(int*)to = 96; to = to + 4; *(int*)to = 1; to = to + 4;
*(int*)to = 2; to = to + 4;
*(int*)to = (int)v_rodata; to = to + 4;
*(int*)to = (int)rodata_off; to = to + 4;
*(int*)to = rodata_size; to = to + 4;
*(int*)to = 0; to = to + 4; *(int*)to = 0; to = to + 4;
*(int*)to = 4; to = to + 4; *(int*)to = 0; to = to + 4;
write(1, buf, to - buf);
return 0;
}