/* SPDX-License-Identifier: GPL-2.0-only */ #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, Accessed, Dirty */ #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; }