tools/patch_libultra_math.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <string.h>
   4 #include <stdint.h>
   5
   6 /* from elf.h */
   7
   8 /* Type for a 16-bit quantity.  */
   9 typedef uint16_t Elf32_Half;
  10
  11 /* Types for signed and unsigned 32-bit quantities.  */
  12 typedef uint32_t Elf32_Word;
  13
  14 /* Type of addresses.  */
  15 typedef uint32_t Elf32_Addr;
  16
  17 /* Type of file offsets.  */
  18 typedef uint32_t Elf32_Off;
  19
  20 /* The ELF file header.  This appears at the start of every ELF file.  */
  21
  22 #define EI_NIDENT (16)
  23
  24 typedef struct
  25 {
  26   unsigned char e_ident[EI_NIDENT];     /* Magic number and other info */
  27   Elf32_Half    e_type;                 /* Object file type */
  28   Elf32_Half    e_machine;              /* Architecture */
  29   Elf32_Word    e_version;              /* Object file version */
  30   Elf32_Addr    e_entry;                /* Entry point virtual address */
  31   Elf32_Off     e_phoff;                /* Program header table file offset */
  32   Elf32_Off     e_shoff;                /* Section header table file offset */
  33   Elf32_Word    e_flags;                /* Processor-specific flags */
  34   Elf32_Half    e_ehsize;               /* ELF header size in bytes */
  35   Elf32_Half    e_phentsize;            /* Program header table entry size */
  36   Elf32_Half    e_phnum;                /* Program header table entry count */
  37   Elf32_Half    e_shentsize;            /* Section header table entry size */
  38   Elf32_Half    e_shnum;                /* Section header table entry count */
  39   Elf32_Half    e_shstrndx;             /* Section header string table index */
  40 } Elf32_Ehdr;
  41
  42 /* Conglomeration of the identification bytes, for easy testing as a word.  */
  43 #define ELFMAG          "\177ELF"
  44 #define SELFMAG         4
  45
  46 #define EI_CLASS        4               /* File class byte index */
  47 #define ELFCLASS32      1               /* 32-bit objects */
  48
  49 #define EI_DATA         5               /* Data encoding byte index */
  50 #define ELFDATA2MSB     2               /* 2's complement, big endian */
  51
  52 /* end from elf.h */
  53
  54 // This file will find all mips3 object files in an ar archive and set the ABI flags to O32
  55 // this allows gcc to link them with the mips2 object files.
  56 // Irix CC doesn't set the elf e_flags properly.
  57
  58 // the AR file is structured as followed
  59 //"!<arch>" followed by 0x0A (linefeed) 8 characters
  60 // then a file header that follows the following structure
  61 // everything is represented using space padded characters
  62 // the last two characters are alwos 0x60 0x0A
  63 // then come the file contents
  64 // you can find the location of the next header by adding file_size_in_bytes (after parsing)
  65 // all file headers start at an even offset so if the file size in bytes is odd you have to add 1
  66 // the first two "files" are special.  One is a symbol table with a pointer to the header of the file
  67 // contaning the symbol the other is an extended list of filenames
  68 struct ar_header {
  69     char identifier[16];
  70     char file_modification_timestamp[12];
  71     char owner_id[6];
  72     char group_id[6];
  73     char file_mode[8];
  74     char file_size_in_bytes[10];
  75     char ending[2];
  76 };
  77
  78 //These constants found by inspecting output of objdump
  79 #define FLAGS_MIPS3 0x20
  80 #define FLAGS_O32ABI 0x100000
  81 int main(int argc, char **argv) {
  82     FILE *f = fopen(argv[1], "r+");
  83
  84     if (f == NULL) {
  85         printf("Failed to open file! %s\n", argv[1]);
  86         return -1;
  87     }
  88     struct ar_header current_header;
  89     fseek(f, 0x8, SEEK_SET); // skip header, this is safe enough given that we check to make sure the
  90                              // file header is valid
  91
  92     while (1 == fread(&current_header, sizeof(current_header), 1, f)) {
  93         if (current_header.ending[0] != 0x60 && current_header.ending[1] != 0x0A) {
  94             printf("Expected file header\n");
  95             return -1;
  96         }
  97         size_t filesize = atoi(current_header.file_size_in_bytes);
  98         Elf32_Ehdr hdr;
  99         if (filesize < sizeof(hdr) || (1 != fread(&hdr, sizeof(hdr), 1, f))) {
 100             printf("Failed to read ELF header\n");
 101             return -1;
 102         }
 103
 104         if (strncmp((const char *) hdr.e_ident, ELFMAG, SELFMAG) == 0) {
 105             // found an ELF file.
 106             if (hdr.e_ident[EI_CLASS] != ELFCLASS32 || hdr.e_ident[EI_DATA] != ELFDATA2MSB) {
 107                 printf("Expected 32bit big endian object files\n");
 108                 return -1;
 109             }
 110
 111             if ((hdr.e_flags & 0xFF) == FLAGS_MIPS3 && (hdr.e_flags & FLAGS_O32ABI) == 0) {
 112                 hdr.e_flags |= FLAGS_O32ABI;
 113                 fseek(f, -sizeof(hdr), SEEK_CUR);
 114                 if (1 != fwrite(&hdr, sizeof(hdr), 1, f)) {
 115                     printf("Failed to write back ELF header after patching.\n");
 116                     return -1;
 117                 }
 118             }
 119         }
 120         if (filesize % 2 == 1)
 121             filesize++;
 122         fseek(f, filesize - sizeof(hdr), SEEK_CUR);
 123     }
 124     fclose(f);
 125     return 0;
 126 }