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/*
* COFF loader.
* Copyright (C) 2023, stsp2@yandex.ru
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <assert.h>
#include "util.h"
#include "coff.h"
#define STUB_DEBUG 0
#if STUB_DEBUG
#define stub_debug(...) printf(__VA_ARGS__)
#else
#define stub_debug(...)
#endif
struct coff_header {
unsigned short f_magic; /* Magic number */
unsigned short f_nscns; /* Number of Sections */
int32_t f_timdat; /* Time & date stamp */
int32_t f_symptr; /* File pointer to Symbol Table */
int32_t f_nsyms; /* Number of Symbols */
unsigned short f_opthdr; /* sizeof(Optional Header) */
unsigned short f_flags; /* Flags */
};
struct opt_header {
unsigned short magic; /* Magic Number */
unsigned short vstamp; /* Version stamp */
uint32_t tsize; /* Text size in bytes */
uint32_t dsize; /* Initialised data size */
uint32_t bsize; /* Uninitialised data size */
uint32_t entry; /* Entry point */
uint32_t text_start; /* Base of Text used for this file */
uint32_t data_start; /* Base of Data used for this file */
};
struct scn_header {
char s_name[8]; /* Section Name */
int32_t s_paddr; /* Physical Address */
int32_t s_vaddr; /* Virtual Address */
int32_t s_size; /* Section Size in Bytes */
int32_t s_scnptr; /* File offset to the Section data */
int32_t s_relptr; /* File offset to the Relocation table for this Section */
int32_t s_lnnoptr; /* File offset to the Line Number table for this Section */
unsigned short s_nreloc; /* Number of Relocation table entries */
unsigned short s_nlnno; /* Number of Line Number table entries */
int32_t s_flags; /* Flags for this section */
};
enum { SCT_TEXT, SCT_DATA, SCT_BSS, SCT_MAX };
static struct scn_header scns[SCT_MAX];
struct coff_h {
uint32_t length;
uint32_t entry;
};
static void read_section(char __far *buf, int ifile, long coffset, int sc)
{
long bytes;
lseek(ifile, coffset + scns[sc].s_scnptr, SEEK_SET);
bytes = _long_read(ifile, buf, scns[sc].s_vaddr,
scns[sc].s_size);
stub_debug("read returned %li\n", bytes);
if (bytes != scns[sc].s_size) {
fprintf(stderr, "err reading %li bytes, got %li\n",
scns[sc].s_size, bytes);
_exit(EXIT_FAILURE);
}
}
static void *read_coff_headers(int ifile)
{
struct coff_header chdr;
struct opt_header ohdr;
struct coff_h *h;
int rc;
rc = read(ifile, &chdr, sizeof(chdr)); /* get the COFF header */
if (rc != sizeof(chdr)) {
fprintf(stderr, "bad COFF header\n");
return NULL;
}
if (chdr.f_opthdr < sizeof(ohdr)) {
fprintf(stderr, "opt header size mismatch: %i %zi\n",
chdr.f_opthdr, sizeof(ohdr));
return NULL;
}
rc = read(ifile, &ohdr, sizeof(ohdr)); /* get the COFF opt header */
if (rc != sizeof(ohdr)) {
fprintf(stderr, "bad COFF opt header\n");
return NULL;
}
if (chdr.f_opthdr > sizeof(ohdr))
lseek(ifile, chdr.f_opthdr - sizeof(ohdr), SEEK_CUR);
rc = read(ifile, scns, sizeof(scns[0]) * SCT_MAX);
if (rc != sizeof(scns[0]) * SCT_MAX) {
fprintf(stderr, "failed to read section headers\n");
return NULL;
}
#if STUB_DEBUG
for (int i = 0; i < SCT_MAX; i++) {
struct scn_header *h = &scns[i];
stub_debug("Section %s pa 0x%lx va 0x%lx size 0x%lx foffs 0x%lx\n",
h->s_name, h->s_paddr, h->s_vaddr, h->s_size, h->s_scnptr);
}
#endif
h = malloc(sizeof(*h));
assert(h);
h->entry = ohdr.entry;
h->length = scns[SCT_BSS].s_vaddr + scns[SCT_BSS].s_size;
return h;
}
static uint32_t get_coff_va(void *handle)
{
return 0; // ???
}
static uint32_t get_coff_length(void *handle)
{
struct coff_h *h = handle;
return h->length;
}
static uint32_t get_coff_entry(void *handle)
{
struct coff_h *h = handle;
return h->entry;
}
static void read_coff_sections(void *handle, char __far *ptr, int ifile,
uint32_t offset)
{
struct coff_h *h = handle;
read_section(ptr, ifile, offset, SCT_TEXT);
read_section(ptr, ifile, offset, SCT_DATA);
farmemset(ptr, scns[SCT_BSS].s_vaddr, 0, scns[SCT_BSS].s_size +
(scns[SCT_BSS].s_size & 1));
free(h);
}
struct ldops coff_ops = {
read_coff_headers,
get_coff_va,
get_coff_length,
get_coff_entry,
read_coff_sections,
};
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