doc: describe COFF file structure
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docs/COFF.org
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69
docs/COFF.org
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#+TITLE: Common Object File Format (COFF)
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** COFF File Structure
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#+begin_src
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+-----------------------+
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| |
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| File Header |
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| |
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+-----------------------+----
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| | \
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| Optional File Header | | Only for executable file
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| (a.out header) | /
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+-----------------------+----
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| | \
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| Section Header 1 | |
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| | |
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+-----------------------+ |
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. . | Section Headers
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. . |
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+-----------------------+ |
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| | |
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| Section Header n | |
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| | /
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+-----------------------+----
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| | \
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| Section 1 Raw Data | |
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| | |
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+-----------------------+ |
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. . | Raw data
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. . | (Executable Code and Initialized Data)
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+-----------------------+ |
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| | |
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| Section n Raw Data | |
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| | /
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+-----------------------+----
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| | \
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| Section 1 Relocation | |
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| Information | |
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+-----------------------+ |
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. . | Relocation
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. . | Information
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+-----------------------+ |
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| | |
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| Section n Relocation | |
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| Information | /
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+-----------------------+----
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| |
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| Symbol Table |
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+-----------------------+
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| |
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| String Table |
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| |
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+-----------------------+
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#+end_src
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*** File Header
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| Type | Description |
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|----------+---------------------------------|
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| uint16_t | Version ID (~0x014c~ for i386) |
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| uint16_t | Number of section headers |
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| uint32_t | Timestamp |
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| uint32_t | Symtab address |
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| uint32_t | Number of entries in the symtab |
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| uint16_t | Optional header size |
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| uint16_t | Flags |
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@ -57,7 +57,7 @@ typedef struct scnhdr
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uint16_t s_nreloc;
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uint16_t s_nlnno;
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int32_t s_flags;
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} SCNHDR;
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} __attribute__((packed)) SCNHDR;
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# define SCNHSZ sizeof(SCNHDR)
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@ -79,7 +79,7 @@ typedef struct reloc
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uint32_t r_vaddr;
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uint32_t r_symndx;
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uint16_t r_type;
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} RELOC;
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} __attribute__((packed)) RELOC;
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# define RELSZ 10
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# define R_ABS 0x000
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@ -96,8 +96,25 @@ typedef struct lineno
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uint32_t l_paddr;
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} l_addr;
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uint16_t l_lnno;
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} LINENO;
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} __attribute__((packed)) LINENO;
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# define LINESZ 6
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typedef struct sym
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{
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uint8_t n_name[8];
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int32_t n_value;
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int16_t n_scnum;
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uint16_t n_type;
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uint8_t n_sclass;
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uint8_t n_numaux;
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} __attribute__((packed)) SYM;
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# define SYMSZ 18
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# define N_UNDEF (0x0)
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# define N_ABS (-0x1)
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# define N_DEBUG (-0x2)
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# define C_EXT 0x2
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# define C_STAT 0x3
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#endif /* !COFF_H */
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@ -5,6 +5,11 @@
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static char *prg_name;
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static char *outfile = "a.out";
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typedef struct section
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{
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} Section;
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static void
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usage(int retcode)
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{
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@ -38,7 +43,9 @@ main(int argc, char **argv)
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FILE *fp;
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FILHDR fhdr;
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SCNHDR shdr;
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AOUTHDR aout;
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uint8_t *buffer;
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SYM entry;
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int idx;
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prg_name = argv[0];
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@ -82,12 +89,31 @@ main(int argc, char **argv)
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if (fhdr.f_opthdr > 0)
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{
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fread(&aout, 1, AOUTHSZ, fp);
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buffer = malloc(fhdr.f_opthdr);
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fread(buffer, 1, fhdr.f_opthdr, fp);
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free(buffer);
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}
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fread(&shdr, 1, SCNHSZ, fp);
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printf("name: %c%c%c%c%c%c%c%c\n", shdr.s_name[0], shdr.s_name[1],shdr.s_name[2],shdr.s_name[3],shdr.s_name[4],shdr.s_name[5],shdr.s_name[6],shdr.s_name[7]);
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printf("flags: 0x%x\n", shdr.s_flags);
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for (idx = 0; idx < fhdr.f_nscns; idx++)
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{
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fread(&shdr, 1, SCNHSZ, fp);
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printf("Section: %c%c%c%c%c%c%c%c\n", shdr.s_name[0], shdr.s_name[1],shdr.s_name[2],shdr.s_name[3],shdr.s_name[4],shdr.s_name[5],shdr.s_name[6],shdr.s_name[7]);
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printf("\tflags: 0x%x\n", shdr.s_flags);
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printf("\tsize: %d\n", shdr.s_size);
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}
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fseek(fp, fhdr.f_symptr, SEEK_SET);
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for (idx = 0; idx < fhdr.f_nsyms; idx++)
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{
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fread(&entry, 1, SYMSZ, fp);
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printf("name: %c%c%c%c%c%c%c%c\n", entry.n_name[0], entry.n_name[1],entry.n_name[2],entry.n_name[3],entry.n_name[4],entry.n_name[5],entry.n_name[6],entry.n_name[7]);
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printf("\tvalue: %d\n", entry.n_value);
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printf("\tscnum: %hd\n", entry.n_scnum);
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printf("\ttype: %hd\n", entry.n_type);
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printf("\tsclass: %d\n", entry.n_sclass);
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printf("\tnumaux: %d\n", entry.n_numaux);
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}
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fclose(fp);
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