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self-relocation in dynamic loader

This commit is contained in:
flysand7 2023-08-04 00:16:15 +11:00
parent bf0d06eeb4
commit 5b2d0c0c9d
7 changed files with 905 additions and 88 deletions
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2
build.py
View File

@ -269,7 +269,7 @@ dl_lib = f'lib/{dl_file}'
if target == 'linux': if target == 'linux':
print_step(f'Compiling {dl_lib}\n') print_step(f'Compiling {dl_lib}\n')
assemble('src/loader/loader-entry.asm', 'bin/loader-entry.o') assemble('src/loader/loader-entry.asm', 'bin/loader-entry.o')
compile(['bin/loader-entry.o', 'src/loader/loader-entry.c'], dl_lib, compile(['bin/loader-entry.o', 'src/loader/loader-self-reloc.c', 'src/loader/loader.c'], dl_lib,
'-shared -nostdlib -Wl,-e,_dlstart -Wl,--sort-section,alignment -Wl,--sort-common -Wl,--gc-sections -Wl,--hash-style=both -Wl,--no-undefined -Wl,--exclude-libs=ALL -fno-stack-protector') '-shared -nostdlib -Wl,-e,_dlstart -Wl,--sort-section,alignment -Wl,--sort-common -Wl,--gc-sections -Wl,--hash-style=both -Wl,--no-undefined -Wl,--exclude-libs=ALL -fno-stack-protector')
print_step(f'Compiling {crt_file}\n') print_step(f'Compiling {crt_file}\n')

618
src/include/bin/elf.h Normal file
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@ -0,0 +1,618 @@
#pragma once
#include <cia-def.h>
typedef u64 Elf64_Addr;
typedef u64 Elf64_Off;
typedef u16 Elf64_Half;
typedef u32 Elf64_Word;
typedef i32 Elf64_Sword;
typedef u64 Elf64_Xword;
typedef i64 Elf64_Sxword;
// e_type definitions
#define ET_NONE 0x0000
#define ET_REL 0x0001
#define ET_EXEC 0x0002
#define ET_DYN 0x0003
#define ET_CORE 0x0004
#define ET_LOOS 0xfe00
#define ET_HIOS 0xfeff
#define ET_LOPROC 0xff00
#define ET_HIPROC 0xffff
// e_machine definitions
#define EM_NONE 0
#define EM_M32 1
#define EM_SPARC 2
#define EM_386 3
#define EM_68K 4
#define EM_88K 5
#define EM_IAMCU 6
#define EM_860 7
#define EM_MIPS 8
#define EM_S370 9
#define EM_MIPS_RS3_LE 10
#define EM_PARISC 15
#define EM_VPP500 17
#define EM_SPARC32PLUS 18
#define EM_960 19
#define EM_PPC 20
#define EM_PPC64 21
#define EM_S390 22
#define EM_SPU 23
#define EM_V800 36
#define EM_FR20 37
#define EM_RH32 38
#define EM_RCE 39
#define EM_ARM 40
#define EM_ALPHA 41
#define EM_SH 42
#define EM_SPARCV9 43
#define EM_TRICORE 44
#define EM_ARC 45
#define EM_H8_300 46
#define EM_H8_300H 47
#define EM_H8S 48
#define EM_H8_500 49
#define EM_IA_64 50
#define EM_MIPS_X 51
#define EM_COLDFIRE 52
#define EM_68HC12 53
#define EM_MMA 54
#define EM_PCP 55
#define EM_NCPU 56
#define EM_NDR1 57
#define EM_STARCORE 58
#define EM_ME16 59
#define EM_ST100 60
#define EM_TINYJ 61
#define EM_X86_64 62
#define EM_PDSP 63
#define EM_PDP10 64
#define EM_PDP11 65
#define EM_FX66 66
#define EM_ST9PLUS 67
#define EM_ST7 68
#define EM_68HC16 69
#define EM_68HC11 70
#define EM_68HC08 71
#define EM_68HC05 72
#define EM_SVX 73
#define EM_ST19 74
#define EM_VAX 75
#define EM_CRIS 76
#define EM_JAVELIN 77
#define EM_FIREPATH 78
#define EM_ZSP 79
#define EM_MMIX 80
#define EM_HUANY 81
#define EM_PRISM 82
#define EM_AVR 83
#define EM_FR30 84
#define EM_D10V 85
#define EM_D30V 86
#define EM_V850 87
#define EM_M32R 88
#define EM_MN10300 89
#define EM_MN10200 90
#define EM_PJ 91
#define EM_OPENRISC 92
#define EM_ARC_COMPACT 93
#define EM_XTENSA 94
#define EM_VIDEOCORE 95
#define EM_TMM_GPP 96
#define EM_NS32K 97
#define EM_TPC 98
#define EM_SNP1K 99
#define EM_ST200 100
#define EM_IP2K 101
#define EM_MAX 102
#define EM_CR 103
#define EM_F2MC16 104
#define EM_MSP430 105
#define EM_BLACKFIN 106
#define EM_SE_C33 107
#define EM_SEP 108
#define EM_ARCA 109
#define EM_UNICORE 110
#define EM_EXCESS 111
#define EM_DXP 112
#define EM_ALTERA_NIOS2 113
#define EM_CRX 114
#define EM_XGATE 115
#define EM_C166 116
#define EM_M16C 117
#define EM_DSPIC30F 118
#define EM_CE 119
#define EM_M32C 120
#define EM_TSK3000 131
#define EM_RS08 132
#define EM_SHARC 133
#define EM_ECOG2 134
#define EM_SCORE7 135
#define EM_DSP24 136
#define EM_VIDEOCORE3 137
#define EM_LATTICEMICO32 138
#define EM_SE_C17 139
#define EM_TI_C6000 140
#define EM_TI_C2000 141
#define EM_TI_C5500 142
#define EM_TI_ARP32 143
#define EM_TI_PRU 144
#define EM_MMDSP_PLUS 160
#define EM_MMDSP_PLUS 160
#define EM_CYPRESS_M8C 161
#define EM_R32C 162
#define EM_TRIMEDIA 163
#define EM_QDSP6 164
#define EM_8051 165
#define EM_STXP7X 166
#define EM_NDS32 167
#define EM_ECOG1 168
#define EM_ECOG1X 168
#define EM_MAXQ30 169
#define EM_XIMO16 170
#define EM_MANIK 171
#define EM_CRAYNV2 172
#define EM_RX 173
#define EM_METAG 174
#define EM_MCST_ELBRUS 175
#define EM_ECOG16 176
#define EM_CR16 177
#define EM_ETPU 178
#define EM_SLE9X 179
#define EM_L10M 180
#define EM_K10M 181
#define EM_AARCH64 183
#define EM_AVR32 185
#define EM_STM8 186
#define EM_TILE64 187
#define EM_TILEPRO 188
#define EM_MICROBLAZE 189
#define EM_CUDA 190
#define EM_TILEGX 191
#define EM_CLOUDSHIELD 192
#define EM_COREA_1ST 193
#define EM_COREA_2ND 194
#define EM_ARC_COMPACT2 195
#define EM_OPEN8 196
#define EM_RL78 197
#define EM_VIDEOCORE5 198
#define EM_78KOR 199
#define EM_56800EX 200
#define EM_BA1 201
#define EM_BA2 202
#define EM_XCORE 203
#define EM_MCHP_PIC 204
#define EM_INTEL205 205
#define EM_INTEL206 206
#define EM_INTEL207 207
#define EM_INTEL208 208
#define EM_INTEL209 209
#define EM_KM32 210
#define EM_KMX32 211
#define EM_KMX16 212
#define EM_KMX8 213
#define EM_KVARC 214
#define EM_CDP 215
#define EM_COGE 216
#define EM_COOL 217
#define EM_NORC 218
#define EM_CSR_KALIMBA 219
#define EM_Z80 220
#define EM_VISIUM 221
#define EM_FT32 222
#define EM_MOXIE 223
#define EM_AMDGPU 224
#define EM_RISCV 243
// e_version identifiers
#define EV_NONE 0
#define EV_CURRENT 1
// e_ident indices
#define EI_MAG0 0
#define EI_MAG1 1
#define EI_MAG2 2
#define EI_MAG3 3
#define EI_CLASS 4
#define EI_DATA 5
#define EI_VERSION 6
#define EI_OSABI 7
#define EI_ABIVERSION 8
#define EI_PAD 9
#define EI_NIDENT 16
// e_ident values
#define ELFMAG0 0x7f
#define ELFMAG1 'E'
#define ELFMAG2 'L'
#define ELFMAG3 'F'
#define ELFCLASSNONE 0
#define ELFCLASS32 1
#define ELFCLASS64 2
#define ELFDATANONE 0
#define ELFDATA2LSB 1
#define ELFDATA2MSB 2
#define ELFOSABI_NONE 0
#define ELFOSABI_HPUX 1
#define ELFOSABI_NETBSD 2
#define ELFOSABI_GNU 3
#define ELFOSABI_LINUX 3
#define ELFOSABI_SOLARIS 6
#define ELFOSABI_AIX 7
#define ELFOSABI_IRIX 8
#define ELFOSABI_FREEBSD 9
#define ELFOSABI_TRU64 10
#define ELFOSABI_MODESTO 11
#define ELFOSABI_OPENBSD 12
#define ELFOSABI_OPENVMS 13
#define ELFOSABI_NSK 14
#define ELFOSABI_AROS 15
#define ELFOSABI_FENIXOS 16
#define ELFOSABI_CLOUDABI 17
#define ELFOSABI_OPENVOS 18
// special section header indices
#define SHN_UNDEF 0x0000
#define SHN_LORESERVE 0xff00
#define SHN_LOPROC 0xff00
#define SHN_HIPROC 0xff1f
#define SHN_LOOS 0xff20
#define SHN_HIOS 0xff3f
#define SHN_ABS 0xfff1
#define SHN_COMMON 0xfff2
#define SHN_XINDEX 0xffff
#define SHN_HIRESERVE 0xffff
// sh_type values
#define SHT_NULL 0
#define SHT_PROGBITS 1
#define SHT_SYMTAB 2
#define SHT_STRTAB 3
#define SHT_RELA 4
#define SHT_HASH 5
#define SHT_DYNAMIC 6
#define SHT_NOTE 7
#define SHT_NOBITS 8
#define SHT_REL 9
#define SHT_SHLIB 10
#define SHT_DYNSYM 11
#define SHT_INIT_ARRAY 14
#define SHT_FINI_ARRAY 15
#define SHT_PREINIT_ARRAY 16
#define SHT_GROUP 17
#define SHT_SYMTAB_SHNDX 18
#define SHT_LOOS 0x60000000
#define SHT_HIOS 0x6fffffff
#define SHT_LOPROC 0x70000000
#define SHT_X86_64_UNWIND 0x70000001
#define SHT_HIPROC 0x7fffffff
#define SHT_LOUSER 0x80000000
#define SHT_HIUSER 0xffffffff
// sh_flags values
#define SHF_WRITE 0x1
#define SHF_ALLOC 0x2
#define SHF_EXECINSTR 0x4
#define SHF_MERGE 0x10
#define SHF_STRINGS 0x20
#define SHF_INFO_LINK 0x40
#define SHF_LINK_ORDER 0x80
#define SHF_OS_NONCONFORMING 0x100
#define SHF_GROUP 0x200
#define SHF_TLS 0x400
#define SHF_COMPRESSED 0x800
#define SHF_MASKOS 0x0ff00000
#define SHF_MASKPROC 0xf0000000
#define SHF_X86_64_LARGE 0x10000000
// ch_type values
#define ELFCOMPRESS_ZLIB 1
#define ELFCOMPRESS_LOOS 0x60000000
#define ELFCOMPRESS_HIOS 0x6fffffff
#define ELFCOMPRESS_LOPROC 0x70000000
#define ELFCOMPRESS_HIPROC 0x7fffffff
// section group flags
#define GRP_COMDAT 0x1
#define GRP_MASKOS 0x0ff00000
#define GRP_MASKPROC 0xf0000000
// special symbol table indices
#define STN_UNDEF 0
// st_info fields
#define ELF64_ST_BIND(i) ((i)>>4)
#define ELF64_ST_TYPE(i) ((i)&0xf)
#define ELF64_ST_INFO(b,t) (((b)<<4)+((t)&0xf))
// st_other fields
#define ELF64_ST_VISIBILITY(o) ((o)&0x3)
// st_info binding
#define STB_LOCAL 0
#define STB_GLOBAL 1
#define STB_WEAK 2
#define STB_LOOS 10
#define STB_HIOS 12
#define STB_LOPROC 13
#define STB_HIPROC 15
// st_info type
#define STT_NOTYPE 0
#define STT_OBJECT 1
#define STT_FUNC 2
#define STT_SECTION 3
#define STT_FILE 4
#define STT_COMMON 5
#define STT_TLS 6
#define STT_LOOS 10
#define STT_HIOS 12
#define STT_LOPROC 13
#define STT_HIPROC 15
// st_info visibility
#define STV_DEFAULT 0
#define STV_INTERNAL 1
#define STV_HIDDEN 2
#define STV_PROTECTED 3
// r_info field extraction
#define ELF64_R_SYM(i) ((i)>>32)
#define ELF64_R_TYPE(i) ((i)&0xffffffffL)
#define ELF64_R_INFO(s,t) (((s)<<32)+((t)&0xffffffffL))
// x86-64 relocation types
#define R_X86_64_NONE 0 // none none
#define R_X86_64_64 1 // word64 S + A
#define R_X86_64_PC32 2 // word32 S + A - P
#define R_X86_64_GOT32 3 // word32 G + A
#define R_X86_64_PLT32 4 // word32 L + A - P
#define R_X86_64_COPY 5 // none none
#define R_X86_64_GLOB_DAT 6 // word64 S
#define R_X86_64_JUMP_SLOT 7 // word64 S
#define R_X86_64_RELATIVE 8 // word64 B + A
#define R_X86_64_GOTPCREL 9 // word32 G + GOT + A - P
#define R_X86_64_32 10 // word32 S + A
#define R_X86_64_32S 11 // word32 S + A
#define R_X86_64_16 12 // word16 S + A
#define R_X86_64_PC16 13 // word16 S + A - P
#define R_X86_64_8 14 // word8 S + A
#define R_X86_64_PC8 15 // word8 S + A - P
#define R_X86_64_DTPMOD64 16 // word64
#define R_X86_64_DTPOFF64 17 // word64
#define R_X86_64_TPOFF64 18 // word64
#define R_X86_64_TLSGD 19 // word32
#define R_X86_64_TLSLD 20 // word32
#define R_X86_64_DTPOFF32 21 // word32
#define R_X86_64_GOTTPOFF 22 // word32
#define R_X86_64_TPOFF32 23 // word32
#define R_X86_64_PC64 24 // word64 S + A - P
#define R_X86_64_GOTOFF64 25 // word64 S + A - GOT
#define R_X86_64_GOTPC32 26 // word32 GOT + A - P
#define R_X86_64_GOT64 27 // word64 G + A
#define R_X86_64_GOTPCREL64 28 // word64 G + GOT - P + A
#define R_X86_64_GOTPC64 29 // word64 GOT - P + A
#define R_X86_64_GOTPLT64 30 // word64 G + A
#define R_X86_64_PLTOFF64 31 // word64 L - GOT + A
#define R_X86_64_SIZE32 32 // word32 Z + A
#define R_X86_64_SIZE64 33 // word64 Z + A
#define R_X86_64_GOTPC32_TLSDESC 34 // word32
#define R_X86_64_TLSDESC_CALL 35 // none
#define R_X86_64_TLSDESC 36 // word64×2
#define R_X86_64_IRELATIVE 37 // word64 indirect (B + A)
// p_type values
#define PT_NULL 0
#define PT_LOAD 1
#define PT_DYNAMIC 2
#define PT_INTERP 3
#define PT_NOTE 4
#define PT_SHLIB 5
#define PT_PHDR 6
#define PT_TLS 7
#define PT_LOOS 0x60000000
#define PT_HIOS 0x6fffffff
#define PT_LOPROC 0x70000000
#define PT_HIPROC 0x7fffffff
// p_flags values
#define PF_X 0x00000001
#define PF_W 0x00000002
#define PF_R 0x00000004
#define PF_MASKOS 0x0ff00000
#define PF_MASKPROC 0xf0000000
// d_tag values
#define DT_NULL 0
#define DT_NEEDED 1
#define DT_PLTRELSZ 2
#define DT_PLTGOT 3
#define DT_HASH 4
#define DT_STRTAB 5
#define DT_SYMTAB 6
#define DT_RELA 7
#define DT_RELASZ 8
#define DT_RELAENT 9
#define DT_STRSZ 10
#define DT_SYMENT 11
#define DT_INIT 12
#define DT_FINI 13
#define DT_SONAME 14
#define DT_RPATH 15
#define DT_SYMBOLIC 16
#define DT_REL 17
#define DT_RELSZ 18
#define DT_RELENT 19
#define DT_PLTREL 20
#define DT_DEBUG 21
#define DT_TEXTREL 22
#define DT_JMPREL 23
#define DT_BIND_NOW 24
#define DT_INIT_ARRAY 25
#define DT_FINI_ARRAY 26
#define DT_INIT_ARRAYSZ 27
#define DT_FINI_ARRAYSZ 28
#define DT_RUNPATH 29
#define DT_FLAGS 30
#define DT_ENCODING 32
#define DT_PREINIT_ARRAY 32
#define DT_PREINIT_ARRAYSZ 33
#define DT_SYMTAB_SHNDX 34
#define DT_LOOS 0x6000000D
#define DT_HIOS 0x6ffff000
#define DT_LOPROC 0x70000000
#define DT_HIPROC 0x7fffffff
// DT_FLAGS values
#define DF_ORIGIN 0x01
#define DF_SYMBOLIC 0x02
#define DF_TEXTREL 0x04
#define DF_BIND_NOW 0x08
#define DF_STATIC_TLS 0x10
// aux entries
#define AT_NULL 0
#define AT_IGNORE 1
#define AT_EXECFD 2
#define AT_PHDR 3
#define AT_PHENT 4
#define AT_PHNUM 5
#define AT_PAGESZ 6
#define AT_BASE 7
#define AT_FLAGS 8
#define AT_ENTRY 9
#define AT_NOTELF 10
#define AT_UID 11
#define AT_EUID 12
#define AT_GID 13
#define AT_EGID 14
#define AT_CLKTCK 17
#define AT_PLATFORM 15
#define AT_HWCAP 16
#define AT_FPUCW 18
#define AT_DCACHEBSIZE 19
#define AT_ICACHEBSIZE 20
#define AT_UCACHEBSIZE 21
#define AT_IGNOREPPC 22
#define AT_SECURE 23
#define AT_BASE_PLATFORM 24
#define AT_RANDOM 25
#define AT_HWCAP2 26
#define AT_EXECFN 31
#define AT_SYSINFO 32
#define AT_SYSINFO_EHDR 33
#define AT_L1I_CACHESHAPE 34
#define AT_L1D_CACHESHAPE 35
#define AT_L2_CACHESHAPE 36
#define AT_L3_CACHESHAPE 37
#define AT_L1I_CACHESIZE 40
#define AT_L1I_CACHEGEOMETRY 41
#define AT_L1D_CACHESIZE 42
#define AT_L1D_CACHEGEOMETRY 43
#define AT_L2_CACHESIZE 44
#define AT_L2_CACHEGEOMETRY 45
#define AT_L3_CACHESIZE 46
#define AT_L3_CACHEGEOMETRY 47
#define AT_MINSIGSTKSZ 51
struct Elf64_Ehdr typedef Elf64_Ehdr;
struct Elf64_Ehdr {
unsigned char e_ident[EI_NIDENT];
Elf64_Half e_type;
Elf64_Half e_machine;
Elf64_Word e_version;
Elf64_Addr e_entry;
Elf64_Off e_phoff;
Elf64_Off e_shoff;
Elf64_Word e_flags;
Elf64_Half e_ehsize;
Elf64_Half e_phentsize;
Elf64_Half e_phnum;
Elf64_Half e_shentsize;
Elf64_Half e_shnum;
Elf64_Half e_shstrndx;
};
struct Elf64_Shdr typedef Elf64_Shdr;
struct Elf64_Shdr {
Elf64_Word sh_name;
Elf64_Word sh_type;
Elf64_Xword sh_flags;
Elf64_Addr sh_addr;
Elf64_Off sh_offset;
Elf64_Xword sh_size;
Elf64_Word sh_link;
Elf64_Word sh_info;
Elf64_Xword sh_addralign;
Elf64_Xword sh_entsize;
};
struct Elf64_Chdr typedef Elf64_Chdr;
struct Elf64_Chdr {
Elf64_Word ch_type;
Elf64_Word ch_reserved;
Elf64_Xword ch_size;
Elf64_Xword ch_addralign;
};
struct Elf64_Sym typedef Elf64_Sym;
struct Elf64_Sym {
Elf64_Word st_name;
unsigned char st_info;
unsigned char st_other;
Elf64_Half st_shndx;
Elf64_Addr st_value;
Elf64_Xword st_size;
};
struct Elf64_Rel typedef Elf64_Rel;
struct Elf64_Rel {
Elf64_Addr r_offset;
Elf64_Xword r_info;
};
struct Elf64_Rela typedef Elf64_Rela;
struct Elf64_Rela {
Elf64_Addr r_offset;
Elf64_Xword r_info;
Elf64_Sxword r_addend;
};
struct Elf64_Phdr typedef Elf64_Phdr;
struct Elf64_Phdr {
Elf64_Word p_type;
Elf64_Word p_flags;
Elf64_Off p_offset;
Elf64_Addr p_vaddr;
Elf64_Addr p_paddr;
Elf64_Xword p_filesz;
Elf64_Xword p_memsz;
Elf64_Xword p_align;
};
struct Elf64_Dyn typedef Elf64_Dyn;
struct Elf64_Dyn {
Elf64_Sxword d_tag;
union {
Elf64_Xword d_val;
Elf64_Addr d_ptr;
} d_un;
};
extern Elf64_Dyn _DYNAMIC[];
struct Elf64_Aux typedef Elf64_Aux;
struct Elf64_Aux {
int a_type;
union {
long a_val;
void *a_ptr;
void (*a_fcn)();
};
};

6
src/loader/loader-entry.asm
View File

@ -4,10 +4,10 @@ bits 64
section .text section .text
default rel default rel
global _dlstart global _dlstart
extern _dlstart_c extern _DYNAMIC:weak
_dlstart: _dlstart:
xor rbp, rbp xor rbp, rbp
mov rdi, rsp mov rdi, rsp
lea rsi, [_dlstart_c wrt ..plt] lea rsi, _DYNAMIC
and rsp, -15 and rsp, -16

84
src/loader/loader-entry.c
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@ -1,84 +0,0 @@
#include <cia-def.h>
#include "syscall.c"
// void *memset(void *dst, int value, u64 num) {
// u8 *bytes = dst;
// for(int i = 0; i != num; ++i) {
// bytes[i] = value;
// }
// return dst;
// }
static void write_char(char c) {
_syscall_write(STDOUT_FILENO, &c, 1);
}
static void write_string(char *str) {
int str_len = 0;
while(str[str_len] != 0) {
str_len += 1;
}
_syscall_write(STDOUT_FILENO, str, str_len);
}
static void write_int(i64 number) {
if(number < 0) {
write_char('-');
number = -number;
}
char buf[20];
buf[19] = 0;
char *p = buf + sizeof buf - 1;
do {
*--p = (number%10) + '0';
number /= 10;
} while(number > 0);
write_string(p);
}
static void write_uint(u64 number) {
char buf[20];
buf[19] = 0;
char *p = buf + sizeof buf - 1;
do {
*--p = (number%10) + '0';
number /= 10;
} while(number > 0);
write_string(p);
}
static void write_hex(u64 number) {
write_string("0x");
char digits[] = "0123456789abcdef";
char buf[20];
buf[19] = 0;
char *p = buf + sizeof buf - 1;
for(int i = 0; i < 64; i += 4) {
if(i != 0 && i % 16 == 0) {
*--p = '\'';
}
u8 bits = (number >> i) & 0x0f;
char digit = digits[bits];
*--p = digit;
}
write_string(p);
}
void _dlstart_c(u64 *sp, void *dynv) {
write_string("Entered dynamic loader\n");
int argc = *sp;
char **argv = (void *)(sp+1);
write_string("We're gonna load an executable: ");
write_string(argv[0]);
write_string("\n");
write_string("With parameters: ");
for(int i = 1; i < argc; ++i) {
if(i != 1) {
write_string(", ");
}
write_string(argv[i]);
}
write_string("\n");
_syscall_exit(0);
}

272
src/loader/loader-self-reloc.c Normal file
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@ -0,0 +1,272 @@
#include <cia-def.h>
#include <stdarg.h>
#include <bin/elf.h>
#include "syscall.c"
#define AUX_CNT 32
#define DYN_CNT 37
struct Elf_Image typedef Elf_Image;
struct Elf_Image {
u8 *base;
u8 *phdr;
u64 ph_num;
u64 ph_ent;
char *name;
};
#define laddr(elf, off) (void *)((elf)->base + off)
static void _dbg_print_char(char c) {
_syscall_write(STDOUT_FILENO, &c, 1);
}
static void _dbg_print_string(char *str) {
int str_len = 0;
while(str[str_len] != 0) {
str_len += 1;
}
_syscall_write(STDOUT_FILENO, str, str_len);
}
static void _dbg_print_string_n(char *str, u64 len) {
_syscall_write(STDOUT_FILENO, str, len);
}
static void _dbg_print_int(i64 number) {
if(number < 0) {
_dbg_print_char('-');
number = -number;
}
char buf[20];
buf[19] = 0;
char *p = buf + sizeof buf - 1;
do {
*--p = (number%10) + '0';
number /= 10;
} while(number > 0);
_dbg_print_string(p);
}
static void _dbg_print_uint(u64 number) {
char buf[20];
buf[19] = 0;
char *p = buf + sizeof buf - 1;
do {
*--p = (number%10) + '0';
number /= 10;
} while(number > 0);
_dbg_print_string(p);
}
static void _dbg_print_hex(u64 number) {
// _dbg_print_string("0x");
char digits[] = "0123456789abcdef";
char buf[20];
buf[19] = 0;
char *p = buf + sizeof buf - 1;
for(int i = 0; i < 64; i += 4) {
if(i != 0 && i % 16 == 0) {
*--p = '_';
}
u8 bits = (number >> i) & 0x0f;
char digit = digits[bits];
*--p = digit;
}
_dbg_print_string(p);
}
static void _dbg_printf(char *fmt, ...) {
va_list args;
va_start(args, fmt);
char str_buf[256];
i64 buf_i = 0;
while(*fmt != 0) {
while(*fmt != '%' && *fmt != 0 && buf_i != sizeof str_buf-1) {
str_buf[buf_i] = *fmt;
buf_i += 1;
fmt++;
}
str_buf[buf_i] = 0;
_dbg_print_string_n(str_buf, buf_i);
buf_i = 0;
if(*fmt == '%') {
++fmt;
if(*fmt == 'd') {
i64 number = va_arg(args, i64);
_dbg_print_int(number);
}
else if(*fmt == 'u') {
u64 number = va_arg(args, u64);
_dbg_print_uint(number);
}
else if(*fmt == 'x') {
u64 number = va_arg(args, u64);
_dbg_print_hex(number);
}
else if(*fmt == 's') {
char *str = va_arg(args, char *);
_dbg_print_string(str);
}
else if(*fmt == 'c') {
int c = va_arg(args, int);
_dbg_print_char(c);
}
++fmt;
}
}
va_end(args);
}
extern void loader_entry(u64 *sp, Elf64_Dyn *dynv, u64 *aux);
void _dlstart_reloc_c(u64 *sp, Elf64_Dyn *dynv) {
_dbg_print_string("Entered dynamic loader\n");
// Find argc, argv in stack
int argc = *sp;
char **argv = (void *)(sp+1);
// Skip over environment
char **envp = argv+argc+1;
int envc = 0;
for(int i = 0; envp[i]; i += 1) {
envc += 1;
}
// Load aux vector, which is responsible
// for holding information for the loader such as
// the location of phdrs or its load address
u64 aux[AUX_CNT];
Elf64_Aux *auxv = (Elf64_Aux *)(envp + envc + 1);
for(int i = 0; i < AUX_CNT; ++i) {
aux[i] = 0;
}
for(int i = 0; auxv[i].a_type != AT_NULL; ++i) {
int aux_type = auxv[i].a_type;
if(aux_type < AUX_CNT) {
aux[aux_type] = auxv[i].a_val;
}
}
// Read the _DYNAMIC vector
u64 dyn[DYN_CNT];
for(int i = 0; i < DYN_CNT; ++i) {
dyn[i] = 0;
}
_dbg_printf("Dynamic section contents:\n");
for(int i = 0; dynv[i].d_tag != DT_NULL; ++i) {
u64 dyn_tag = dynv[i].d_tag;
_dbg_printf(" %x: %x\n", dyn_tag, dynv[i].d_un.d_val);
if(dyn_tag < DYN_CNT) {
dyn[dyn_tag] = dynv[i].d_un.d_val;
}
}
// Find the dynamic section
if(dynv == NULL) {
_dbg_printf("_DYNAMIC section wasn't found in dynamic loader\n");
}
// If the dynamic linker is not invoked as a command
// It's load address can't be found in the aux vector
// Therefore we compute the base as the difference
// between &_DYNAMIC and it's p_vaddr
u8 *base = (void *)aux[AT_BASE];
if(base == NULL) {
_dbg_printf("trying to find base\n");
u8 *phdrs = (void *)aux[AT_PHDR];
u64 ph_ent = aux[AT_PHENT];
u64 ph_num = aux[AT_PHNUM];
for(int i = 1; i < ph_num; ++i) {
u64 ph_off = i * ph_ent;
Elf64_Phdr *ph = (void *)(phdrs + ph_off);
if(ph->p_type == PT_DYNAMIC) {
_dbg_printf("_DYNAMIC vaddr: %x\n", ph->p_vaddr);
base = (void *)(dynv - ph->p_vaddr);
}
}
}
_dbg_printf("ld-cia.so base: %x\n", base);
_dbg_printf("ld-cia.so _dynamic: %x\n", dynv);
Elf64_Sym *symtab = symtab = (void *)(base + dyn[DT_SYMTAB]);
if(symtab == NULL) {
_dbg_printf("ERROR: No .dynsym found\n");
}
// Apply relocations
if(dyn[DT_REL] != 0) {
_dbg_printf("REL Relocations found. This part isn't implemented\n");
u8 *rel_ents = (void *)(base + dyn[DT_REL]);
u64 rel_ent = dyn[DT_RELENT];
u64 rel_size = dyn[DT_RELSZ];
u64 rel_offs = 0;
while(rel_offs < rel_size) {
Elf64_Rel *rel = (void *)(rel_ents + rel_offs);
u64 offs = rel->r_offset;
u32 sym = ELF64_R_SYM(rel->r_info);
u32 type = ELF64_R_TYPE(rel->r_info);
_dbg_printf(" rel sym: %d type %d\n", sym, type);
// TODO: if needed
rel_offs += rel_ent;
}
}
if(dyn[DT_RELA] != 0) {
_dbg_printf("RELA Relocations found\n");
u8 *rela_ents = (void *)(base + dyn[DT_RELA]);
u64 rela_ent = dyn[DT_RELAENT];
u64 rela_size = dyn[DT_RELASZ];
u64 rela_offs = 0;
while(rela_offs < rela_size) {
Elf64_Rela *rela = (void *)(rela_ents + rela_offs);
u64 reloc_offs = rela->r_offset;
u64 addend = rela->r_addend;
u32 sym_idx = ELF64_R_SYM(rela->r_info);
u32 type = ELF64_R_TYPE(rela->r_info);
_dbg_printf(" rela sym: %x, rela offs: %x, type: %d, addend: %d\n",
sym_idx, reloc_offs, type, addend
);
if(type == R_X86_64_GLOB_DAT) {
Elf64_Sym *sym = &symtab[sym_idx];
void *sym_addr = (void *)(base + sym->st_value);
void **reloc_addr = (void *)(base + reloc_offs);
_dbg_printf(" -> resolving with %x\n", sym_addr);
*reloc_addr = sym_addr;
}
rela_offs += rela_ent;
}
}
if(dyn[DT_PLTGOT] != 0) {
_dbg_printf("PLT relocations found\n");
if(dyn[DT_PLTREL] == DT_REL) {
_dbg_printf(" PLT relocations use relocations of type REL\n");
}
else if(dyn[DT_PLTREL] == DT_RELA) {
_dbg_printf(" PLT relocations use relocations of type RELA\n");
}
_dbg_printf("plt: %x, rela.plt: %x, rela.pltsz: %x\n", dyn[DT_PLTGOT], dyn[DT_JMPREL], dyn[DT_PLTRELSZ]);
void *plt = (void *)(base + dyn[DT_PLTGOT]);
void *rela_plt = (void *)(base + dyn[DT_JMPREL]);
u64 rela_ent = sizeof(Elf64_Rela);
u64 rela_size = dyn[DT_PLTRELSZ];
u64 rela_offs = 0;
while(rela_offs < rela_size) {
Elf64_Rela *rela = (void *)(rela_plt + rela_offs);
u64 reloc_offs = rela->r_offset;
u64 addend = rela->r_addend;
u32 sym_idx = ELF64_R_SYM(rela->r_info);
u32 type = ELF64_R_TYPE(rela->r_info);
_dbg_printf(" rela sym: %x, rela offs: %x, type: %d, addend: %d\n",
sym_idx, reloc_offs, type, addend
);
if(type == R_X86_64_JUMP_SLOT) {
Elf64_Sym *sym = &symtab[sym_idx];
void *sym_addr = (void *)(base + sym->st_value);
void **reloc_addr = (void *)(base + reloc_offs);
_dbg_printf(" -> resolving with %x\n", sym_addr);
*reloc_addr = sym_addr;
}
rela_offs += rela_ent;
_dbg_printf("%x\n", rela_offs);
}
}
_dbg_printf("Self-relocation finished. Entering the loader\n");
loader_entry(sp, dynv, aux);
_syscall_exit(0);
}

10
src/loader/loader.c Normal file
View File

@ -0,0 +1,10 @@
#include <cia-def.h>
#include <bin/elf.h>
#include "syscall.c"
void loader_entry(u64 *sp, Elf64_Dyn *dynv, u64 *aux) {
char str[] = "Hello world??\n";
_syscall_write(STDOUT_FILENO, str, sizeof str);
_syscall_exit(0);
}

1
src/loader/syscall.c
View File

@ -3,6 +3,7 @@
#include <asm/signal.h> #include <asm/signal.h>
#include <asm/ioctls.h> #include <asm/ioctls.h>
#include <asm/mman.h> #include <asm/mman.h>
#include <fcntl.h>
#include <linux/fs.h> #include <linux/fs.h>
#include <linux/loop.h> #include <linux/loop.h>
#include <linux/time.h> #include <linux/time.h>