135 lines
3.1 KiB
C
135 lines
3.1 KiB
C
#include "elf_header.h"
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#include "elf_osabi.h"
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#include <stdio.h>
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#include <string.h>
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#define ELF_IDENTITIFCATION_MAX_SIZE 16
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#define ELF_CLASS_TYPE32 1
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#define ELF_CLASS_TYPE64 2
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#define ELF_BYTE_ORDER_LSB 1
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#define ELF_BYTE_ORDER_MSB 2
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typedef enum EIdent
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{
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EI_MAG0 = 0, //Magic number position zero - three.
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EI_MAG1 = 1,
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EI_MAG2 = 2,
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EI_MAG3 = 3,
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EI_CLASS = 4,
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EI_DATA = 5,
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EI_HEADER_VERSION = 6,
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EI_OSABI = 7,
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EI_ABIVERSION = 8,
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EI_PAD = 9,
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EI_NIDENT = ELF_IDENTITIFCATION_MAX_SIZE - 1, //End of reserved 16 bytes for the header.
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EI_TYPE = EI_NIDENT + 1,
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EI_MACHINE = EI_TYPE + 2,
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EI_OBJECT_FILE_VERSION = EI_MACHINE + 2,
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EI_ENTRY_ADDRESS_POINT = EI_OBJECT_FILE_VERSION + 4
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} ELFIdentOffsets;
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struct elf_header {
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unsigned char Identitication[ELF_IDENTITIFCATION_MAX_SIZE];
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uint32_t FileType;
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uint32_t ISA;
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uint32_t ELFVersion;
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uint64_t EntryAddress;
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uint64_t ProgramHeaderOffset;
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uint64_t SectionHeaderOffset;
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uint32_t Flags;
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};
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struct elf_header* CreateELFHeader(void);
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int ELFMagicNumberValid(const unsigned char* ident);
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void ELFPrintMagic(const struct elf_header* header);
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struct elf_header* ParseObjectFile(const char* bytes, size_t count) {
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if (count < 0x40) return NULL;
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struct elf_header* header = CreateELFHeader();
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memcpy(header, bytes, ELF_IDENTITIFCATION_MAX_SIZE);
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if (!ELFMagicNumberValid(header->Identitication))
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{
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fprintf(stderr, "Failed to find ELF magic number in file header.\n");
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ELFPrintMagic(header);
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printf("\n");
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return NULL;
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}
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switch(bytes[EI_CLASS])
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{
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case ELF_CLASS_TYPE32:
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memcpy(&header->EntryAddress, &bytes[EI_ENTRY_ADDRESS_POINT], sizeof(int32_t));
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break;
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case ELF_CLASS_TYPE64:
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memcpy(&header->EntryAddress, &bytes[EI_ENTRY_ADDRESS_POINT], sizeof(int64_t));
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break;
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default:
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header->EntryAddress = -1;
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}
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switch(bytes[EI_DATA])
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{
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case ELF_BYTE_ORDER_LSB:
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printf("Data: 2's complement, little endian.\n");
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break;
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case ELF_BYTE_ORDER_MSB:
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printf("Data: 2's complement, big endian.\n");
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break;
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default:
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printf("Data: Unknown byte order\n");
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}
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if (bytes[EI_HEADER_VERSION] == 1) printf("ELF File Version: Current (1)\n");
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else printf("ELF File Version: Invalid (%d)\n", bytes[EI_HEADER_VERSION]);
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char buffer[255];
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GetELFOSABIString(bytes[EI_OSABI], buffer);
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printf("OS ABI: %s\n", buffer);
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// int64_t entryAddress;
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// memcpy(&entryAddress, &bytes[EI_ENTRY_ADDRESS_POINT], sizeof(int64_t));
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// printf("Entry point address: %#06lx\n", entryAddress);
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return header;
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}
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int ELFMagicNumberValid(const unsigned char* ident) {
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char magic[5] = { ident[EI_MAG0], ident[EI_MAG1], ident[EI_MAG2], ident[EI_MAG3], '\0' };
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return strcmp(magic, "\x7f""ELF") == 0;
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}
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void ELFPrintMagic(const struct elf_header* header) {
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if (!header) return;
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printf("Magic: ");
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for(int i = 0; i < ELF_IDENTITIFCATION_MAX_SIZE; i++)
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{
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printf("%02X ", header->Identitication[i]);
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}
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printf("\n");
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}
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struct elf_header* CreateELFHeader(void) {
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struct elf_header* header = calloc(sizeof(struct elf_header), 1);
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if (!header)
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{
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fprintf(stderr, "Failed to calloc\n");
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exit(1);
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}
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return header;
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} |