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-rw-r--r--util/pgtblgen/pgtblgen.c168
1 files changed, 168 insertions, 0 deletions
diff --git a/util/pgtblgen/pgtblgen.c b/util/pgtblgen/pgtblgen.c
new file mode 100644
index 0000000000..efbad55204
--- /dev/null
+++ b/util/pgtblgen/pgtblgen.c
@@ -0,0 +1,168 @@
+/*
+ * This file is part of pgtblgen.
+ *
+ * Copyright (c) 2019 Patrick Rudolph <siro@das-labor.org>
+ *
+ * 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 architecure. Supported: x86_64\n");
+ printf(" -b\t base address\n");
+ printf(" -b\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 PS (1ULL << 7)
+#define _GEN_DIR(a) (PRES | RW | US | (a))
+#define _GEN_PAGE(a) (PRES | RW | US | PS | (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;
+}