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/* This file is part of pgtblgen. */
/*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* 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.
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <inttypes.h>
static void usage(char *argv[])
{
printf("usage: %s -b <addr> -a <arch> -o <file>\n", argv[0]);
printf(" -a\t architecture. Supported: x86_64\n");
printf(" -b\t base address\n");
printf(" -o\t the file to write to\n");
printf(" -h\t show this help text\n");
}
/*
* For reference see "AMD64 ArchitectureProgrammer's Manual Volume 2",
* Document 24593-Rev. 3.31-July 2019 Chapter 5.3.4
*
* Page table attributes: WB, User+Supervisor, Present, Writeable
*/
#define _PRES (1ULL << 0)
#define _RW (1ULL << 1)
#define _US (1ULL << 2)
#define _A (1ULL << 5)
#define _D (1ULL << 6)
#define _PS (1ULL << 7)
#define _GEN_DIR(a) (_PRES | _RW | _US | _A | (a))
#define _GEN_PAGE(a) (_PRES | _RW | _US | _PS | _A | _D | (a))
/*
* Generate x86_64 page tables.
* The page tables needs to be placed at @base_address, and identity map
* the first @size_gib GiB of physical memory.
*/
static int gen_pgtbl_x86_64(const uint64_t base_address,
const size_t size_gib,
void **out_buf,
size_t *out_size)
{
uint64_t *entry;
if (!out_size || !out_buf)
return 1;
*out_size = (size_gib + 2) * 4096;
*out_buf = malloc(*out_size);
if (!*out_buf)
return 1;
memset(*out_buf, 0, *out_size);
entry = (uint64_t *)*out_buf;
/* Generate one PM4LE entry - point to PDPE */
entry[0] = _GEN_DIR(base_address + 4096);
entry += 512;
/* PDPE table - point to PDE */
for (size_t i = 0; i < size_gib; i++)
entry[i] = _GEN_DIR(base_address + 4096 * (i + 2));
entry += 512;
/* PDE tables - identity map 2MiB pages */
for (size_t g = 0; g < size_gib; g++) {
for (size_t i = 0; i < 512; i++) {
uint64_t addr = ((1ULL << (12 + 9)) * i) | ((1ULL << (12 + 9 + 9)) * g);
entry[i] = _GEN_PAGE(addr);
}
entry += 512;
}
return 0;
}
int main(int argc, char *argv[])
{
int ret = 1;
uint64_t base_address = 0;
char *filename = NULL;
char *arch = NULL;
void *buf = NULL;
size_t buf_size = 0;
int c;
while ((c = getopt(argc, argv, "ho:a:b:")) != -1)
switch (c) {
case '?': /* falltrough */
case 'h':
usage(argv);
return 0;
case 'o':
filename = optarg;
break;
case 'a':
arch = optarg;
break;
case 'b':
base_address = strtoull(optarg, NULL, 0);
break;
default:
break;
}
if (!filename) {
fprintf(stderr, "E: Missing filename.\n");
goto done;
}
if (!arch) {
fprintf(stderr, "E: Missing architecture.\n");
goto done;
} else if (strcmp(arch, "x86_64") != 0) {
fprintf(stderr, "E: Unsupported architecture.\n");
goto done;
}
if (base_address & 4095) {
fprintf(stderr, "E: Base address not 4 KiB aligned\n");
goto done;
}
/* FIXME: Identity map 4GiB for now, increase if necessary */
if (strcmp(arch, "x86_64") == 0)
ret = gen_pgtbl_x86_64(base_address, 4, &buf, &buf_size);
if (ret) {
fprintf(stderr, "Failed to generate page tables\n");
goto done;
}
// write the table
FILE *fd = fopen(filename, "wb");
if (!fd) {
fprintf(stderr, "%s open failed: %s\n", filename, strerror(errno));
goto done;
}
if (fwrite(buf, 1, buf_size, fd) != buf_size) {
fprintf(stderr, "%s write failed: %s\n", filename, strerror(errno));
fclose(fd);
goto done;
}
if (fclose(fd)) {
fprintf(stderr, "%s close failed: %s\n", filename, strerror(errno));
goto done;
}
ret = 0;
done:
free(buf);
return ret;
}
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