159 lines
3.5 KiB
C
159 lines
3.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <inttypes.h>
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#include <getopt.h>
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static void usage(char *argv[])
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{
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printf("usage: %s -b <addr> -a <arch> -o <file>\n", argv[0]);
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printf(" -a\t architecture. Supported: x86_64\n");
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printf(" -b\t base address\n");
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printf(" -o\t the file to write to\n");
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printf(" -h\t show this help text\n");
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}
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/*
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* For reference see "AMD64 ArchitectureProgrammer's Manual Volume 2",
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* Document 24593-Rev. 3.31-July 2019 Chapter 5.3.4
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*
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* Page table attributes: WB, User+Supervisor, Present, Writeable, Accessed, Dirty
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*/
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#define _PRES (1ULL << 0)
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#define _RW (1ULL << 1)
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#define _US (1ULL << 2)
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#define _A (1ULL << 5)
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#define _D (1ULL << 6)
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#define _PS (1ULL << 7)
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#define _GEN_DIR(a) (_PRES | _RW | _US | _A | (a))
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#define _GEN_PAGE(a) (_PRES | _RW | _US | _PS | _A | _D | (a))
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/*
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* Generate x86_64 page tables.
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* The page tables needs to be placed at @base_address, and identity map
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* the first @size_gib GiB of physical memory.
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*/
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static int gen_pgtbl_x86_64(const uint64_t base_address,
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const size_t size_gib,
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void **out_buf,
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size_t *out_size)
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{
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uint64_t *entry;
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if (!out_size || !out_buf)
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return 1;
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*out_size = (size_gib + 2) * 4096;
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*out_buf = malloc(*out_size);
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if (!*out_buf)
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return 1;
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memset(*out_buf, 0, *out_size);
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entry = (uint64_t *)*out_buf;
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/* Generate one PM4LE entry - point to PDPE */
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entry[0] = _GEN_DIR(base_address + 4096);
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entry += 512;
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/* PDPE table - point to PDE */
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for (size_t i = 0; i < size_gib; i++)
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entry[i] = _GEN_DIR(base_address + 4096 * (i + 2));
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entry += 512;
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/* PDE tables - identity map 2MiB pages */
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for (size_t g = 0; g < size_gib; g++) {
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for (size_t i = 0; i < 512; i++) {
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uint64_t addr = ((1ULL << (12 + 9)) * i) | ((1ULL << (12 + 9 + 9)) * g);
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entry[i] = _GEN_PAGE(addr);
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}
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entry += 512;
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}
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return 0;
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}
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int main(int argc, char *argv[])
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{
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int ret = 1;
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uint64_t base_address = 0;
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char *filename = NULL;
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char *arch = NULL;
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void *buf = NULL;
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size_t buf_size = 0;
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int c;
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while ((c = getopt(argc, argv, "ho:a:b:")) != -1)
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switch (c) {
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case '?': /* falltrough */
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case 'h':
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usage(argv);
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return 0;
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case 'o':
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filename = optarg;
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break;
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case 'a':
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arch = optarg;
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break;
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case 'b':
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base_address = strtoull(optarg, NULL, 0);
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break;
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default:
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break;
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}
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if (!filename) {
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fprintf(stderr, "E: Missing filename.\n");
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goto done;
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}
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if (!arch) {
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fprintf(stderr, "E: Missing architecture.\n");
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goto done;
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} else if (strcmp(arch, "x86_64") != 0) {
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fprintf(stderr, "E: Unsupported architecture.\n");
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goto done;
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}
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if (base_address & 4095) {
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fprintf(stderr, "E: Base address not 4 KiB aligned\n");
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goto done;
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}
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/* FIXME: Identity map 4GiB for now, increase if necessary */
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if (strcmp(arch, "x86_64") == 0)
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ret = gen_pgtbl_x86_64(base_address, 4, &buf, &buf_size);
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if (ret) {
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fprintf(stderr, "Failed to generate page tables\n");
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goto done;
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}
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// write the table
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FILE *fd = fopen(filename, "wb");
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if (!fd) {
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fprintf(stderr, "%s open failed: %s\n", filename, strerror(errno));
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goto done;
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}
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if (fwrite(buf, 1, buf_size, fd) != buf_size) {
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fprintf(stderr, "%s write failed: %s\n", filename, strerror(errno));
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fclose(fd);
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goto done;
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}
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if (fclose(fd)) {
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fprintf(stderr, "%s close failed: %s\n", filename, strerror(errno));
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goto done;
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}
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ret = 0;
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done:
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free(buf);
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return ret;
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}
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