sm64/tools/patch_elf_32bit.c
2021-07-12 23:17:54 -04:00

162 lines
5.2 KiB
C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#define ARMAG "!<arch>\n"
#define SARMAG 8
/* from elf.h */
/* Type for a 16-bit quantity. */
typedef uint16_t Elf32_Half;
/* Types for signed and unsigned 32-bit quantities. */
typedef uint32_t Elf32_Word;
/* Type of addresses. */
typedef uint32_t Elf32_Addr;
/* Type of file offsets. */
typedef uint32_t Elf32_Off;
/* The ELF file header. This appears at the start of every ELF file. */
#define EI_NIDENT (16)
typedef struct
{
unsigned char e_ident[EI_NIDENT]; /* Magic number and other info */
Elf32_Half e_type; /* Object file type */
Elf32_Half e_machine; /* Architecture */
Elf32_Word e_version; /* Object file version */
Elf32_Addr e_entry; /* Entry point virtual address */
Elf32_Off e_phoff; /* Program header table file offset */
Elf32_Off e_shoff; /* Section header table file offset */
Elf32_Word e_flags; /* Processor-specific flags */
Elf32_Half e_ehsize; /* ELF header size in bytes */
Elf32_Half e_phentsize; /* Program header table entry size */
Elf32_Half e_phnum; /* Program header table entry count */
Elf32_Half e_shentsize; /* Section header table entry size */
Elf32_Half e_shnum; /* Section header table entry count */
Elf32_Half e_shstrndx; /* Section header string table index */
} Elf32_Ehdr;
/* Conglomeration of the identification bytes, for easy testing as a word. */
#define ELFMAG "\177ELF"
#define SELFMAG 4
#define EI_CLASS 4 /* File class byte index */
#define ELFCLASS32 1 /* 32-bit objects */
#define EI_DATA 5 /* Data encoding byte index */
#define ELFDATA2MSB 2 /* 2's complement, big endian */
/* end from elf.h */
// This file will find all mips3 object files in an ar archive and set the ABI flags to O32
// this allows gcc to link them with the mips2 object files.
// Irix CC doesn't set the elf e_flags properly.
// the AR file is structured as followed
//"!<arch>" followed by 0x0A (linefeed) 8 characters
// then a file header that follows the following structure
// everything is represented using space padded characters
// the last two characters are alwos 0x60 0x0A
// then come the file contents
// you can find the location of the next header by adding file_size_in_bytes (after parsing)
// all file headers start at an even offset so if the file size in bytes is odd you have to add 1
// the first two "files" are special. One is a symbol table with a pointer to the header of the file
// contaning the symbol the other is an extended list of filenames
struct ar_header {
char identifier[16];
char file_modification_timestamp[12];
char owner_id[6];
char group_id[6];
char file_mode[8];
char file_size_in_bytes[10];
char ending[2];
};
//These constants found by inspecting output of objdump
#define FLAGS_MIPS3 0x20
#define FLAGS_O32ABI 0x100000
int fix_mips_elf(FILE *f, size_t filesize)
{
Elf32_Ehdr hdr;
if (filesize < sizeof(hdr) || (1 != fread(&hdr, sizeof(hdr), 1, f))) {
printf("Failed to read ELF header\n");
return -1;
}
if (strncmp((const char *) hdr.e_ident, ELFMAG, SELFMAG) == 0) {
// found an ELF file.
if (hdr.e_ident[EI_CLASS] != ELFCLASS32 || hdr.e_ident[EI_DATA] != ELFDATA2MSB) {
printf("Expected 32bit big endian object files\n");
return -1;
}
if ((hdr.e_flags & 0xFF) == FLAGS_MIPS3 && (hdr.e_flags & FLAGS_O32ABI) == 0) {
hdr.e_flags |= FLAGS_O32ABI;
fseek(f, -(long)sizeof(hdr), SEEK_CUR);
if (1 != fwrite(&hdr, sizeof(hdr), 1, f)) {
printf("Failed to write back ELF header after patching.\n");
return -1;
}
}
}
return 0;
}
int fix_mips_ar(FILE *f)
{
struct ar_header current_header;
fseek(f, 0x8, SEEK_SET); // skip header, this is safe enough given that we check to make sure the
// file header is valid
while (1 == fread(&current_header, sizeof(current_header), 1, f)) {
if (current_header.ending[0] != 0x60 && current_header.ending[1] != 0x0A) {
printf("Expected file header\n");
return -1;
}
size_t filesize = atoi(current_header.file_size_in_bytes);
if (fix_mips_elf(f, filesize)) {
return -1;
}
if (filesize % 2 == 1)
filesize++;
fseek(f, filesize - sizeof(Elf32_Ehdr), SEEK_CUR);
}
return 0;
}
int main(int argc, char **argv) {
FILE *f = fopen(argv[1], "r+b");
uint8_t magic[8];
int status = 0;
if (f == NULL) {
printf("Failed to open file! %s\n", argv[1]);
return -1;
}
if (1 != fread(&magic, sizeof(magic), 1, f)) {
printf("Failed to read file magic\n");
return -1;
}
rewind(f);
if (!memcmp(ARMAG, magic, SARMAG)) {
status = fix_mips_ar(f);
} else if (!memcmp(ELFMAG, magic, SELFMAG)) {
fseek(f, 0, SEEK_END);
size_t filesize = ftell(f);
rewind(f);
status = fix_mips_elf(f, filesize);
} else {
printf("Unknown file magic: %02x%02x%02X%02X\n", magic[0], magic[1], magic[2], magic[3]);
status = -1;
}
fclose(f);
return status;
}