Edit
IABSD.fr/src/usr.sbin/rdsetroot/rdsetroot.c
sunil
- usr.sbin/rdsetroot/rdsetroot.c
-
/* $OpenBSD: rdsetroot.c,v 1.2 2019/04/16 06:09:52 sunil Exp $ */ /* * Copyright (c) 2019 Sunil Nimmagadda <sunil@openbsd.org> * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include <sys/mman.h> #include <sys/stat.h> #include <err.h> #include <fcntl.h> #include <gelf.h> #include <libelf.h> #include <stdio.h> #include <stdint.h> #include <stdlib.h> #include <string.h> #include <unistd.h> int find_rd_root_image(uint64_t *, uint64_t *, off_t *, size_t *); int symbol_get_u64(const char *, uint64_t *); __dead void usage(void); Elf *e; Elf_Scn *symtab; size_t nsymb, strtabndx, strtabsz; int main(int argc, char **argv) { GElf_Shdr shdr; Elf_Scn *scn; char *dataseg, *kernel = NULL, *fs = NULL, *name; off_t mmap_off, rd_root_size_val; size_t shstrndx, mmap_size; uint64_t rd_root_size_off, rd_root_image_off; uint32_t *ip; int ch, debug = 0, fsfd, kfd, n, xflag = 0; while ((ch = getopt(argc, argv, "dx")) != -1) { switch (ch) { case 'd': debug = 1; break; case 'x': xflag = 1; break; default: usage(); } } argc -= optind; argv += optind; if (argc == 1) kernel = argv[0]; else if (argc == 2) { kernel = argv[0]; fs = argv[1]; } else usage(); if ((kfd = open(kernel, xflag ? O_RDONLY : O_RDWR, 0644)) < 0) err(1, "%s", kernel); if (fs) { if (xflag) fsfd = open(fs, O_RDWR | O_CREAT | O_TRUNC, 0644); else fsfd = open(fs, O_RDONLY, 0644); } else { if (xflag) fsfd = dup(STDOUT_FILENO); else fsfd = dup(STDIN_FILENO); } if (fsfd < 0) err(1, "%s", fs); if (pledge("stdio", NULL) == -1) err(1, "pledge"); if (elf_version(EV_CURRENT) == EV_NONE) errx(1, "elf_version: %s", elf_errmsg(-1)); if ((e = elf_begin(kfd, xflag ? ELF_C_READ : ELF_C_RDWR, NULL)) == NULL) errx(1, "elf_begin: %s", elf_errmsg(-1)); if (elf_kind(e) != ELF_K_ELF) errx(1, "%s: not an elf", kernel); if (gelf_getclass(e) == ELFCLASSNONE) errx(1, "%s: invalid elf, not 32 or 64 bit", kernel); /* Retrieve index of section name string table. */ if (elf_getshdrstrndx(e, &shstrndx) != 0) errx(1, "elf_getshdrstrndx: %s", elf_errmsg(-1)); /* Find symbol table, string table. */ scn = symtab = NULL; while ((scn = elf_nextscn(e, scn)) != NULL) { if (gelf_getshdr(scn, &shdr) != &shdr) errx(1, "elf_getshdr: %s", elf_errmsg(-1)); if ((name = elf_strptr(e, shstrndx, shdr.sh_name)) == NULL) errx(1, "elf_strptr: %s", elf_errmsg(-1)); if (strcmp(name, ELF_SYMTAB) == 0 && shdr.sh_type == SHT_SYMTAB && shdr.sh_entsize != 0) { symtab = scn; nsymb = shdr.sh_size / shdr.sh_entsize; } if (strcmp(name, ELF_STRTAB) == 0 && shdr.sh_type == SHT_STRTAB) { strtabndx = elf_ndxscn(scn); strtabsz = shdr.sh_size; } } if (symtab == NULL) errx(1, "symbol table not found"); if (strtabndx == 0) errx(1, "string table not found"); if (find_rd_root_image(&rd_root_size_off, &rd_root_image_off, &mmap_off, &mmap_size) != 0) errx(1, "can't locate space for rd_root_image!"); if (debug) { fprintf(stderr, "rd_root_size_off: 0x%llx\n", rd_root_size_off); fprintf(stderr, "rd_root_image_off: 0x%llx\n", rd_root_image_off); } /* * Map in the whole data segment. * The file offset needs to be page aligned. */ dataseg = mmap(NULL, mmap_size, xflag ? PROT_READ : PROT_READ | PROT_WRITE, MAP_SHARED, kfd, mmap_off); if (dataseg == MAP_FAILED) err(1, "%s: cannot map data seg", kernel); /* * Find value in the location: rd_root_size */ ip = (uint32_t *) (dataseg + rd_root_size_off); rd_root_size_val = *ip; if (debug) { fprintf(stderr, "rd_root_size val: 0x%llx (%lld blocks)\n", (unsigned long long)rd_root_size_val, (unsigned long long)rd_root_size_val >> 9); fprintf(stderr, "copying root image...\n"); } if (xflag) { n = write(fsfd, dataseg + rd_root_image_off, (size_t)rd_root_size_val); if (n != rd_root_size_val) err(1, "write"); } else { struct stat sstat; if (fstat(fsfd, &sstat) == -1) err(1, "fstat"); if (S_ISREG(sstat.st_mode) && sstat.st_size > rd_root_size_val) { fprintf(stderr, "ramdisk too small 0x%llx 0x%llx\n", (unsigned long long)sstat.st_size, (unsigned long long)rd_root_size_val); exit(1); } n = read(fsfd, dataseg + rd_root_image_off, (size_t)rd_root_size_val); if (n < 0) err(1, "read"); msync(dataseg, mmap_size, 0); } if (debug) fprintf(stderr, "...copied %d bytes\n", n); elf_end(e); return 0; } int find_rd_root_image(uint64_t *rd_root_size_off, uint64_t *rd_root_image_off, off_t *pmmap_off, size_t *pmmap_size) { GElf_Phdr phdr; size_t i, phdrnum; unsigned long kernel_start, kernel_size; uint64_t adiff, rd_root_size, rd_root_image, size_off, image_off; int error = 1; if (symbol_get_u64("rd_root_size", &rd_root_size) != 0) errx(1, "no rd_root_image symbols?"); if (symbol_get_u64("rd_root_image", &rd_root_image) != 0) errx(1, "no rd_root_image symbols?"); /* Retrieve number of program headers. */ if (elf_getphdrnum(e, &phdrnum) != 0) errx(1, "elf_getphdrnum: %s", elf_errmsg(-1)); /* Locate the data segment. */ for (i = 0; i < phdrnum; i++) { if (gelf_getphdr(e, i, &phdr) != &phdr) errx(1, "gelf_getphdr: %s", elf_errmsg(-1)); if (phdr.p_type != PT_LOAD) continue; kernel_start = phdr.p_paddr; kernel_size = phdr.p_filesz; adiff = phdr.p_vaddr - phdr.p_paddr; size_off = rd_root_size - kernel_start; image_off = rd_root_image - kernel_start; if (size_off < adiff || image_off < adiff) continue; size_off -= adiff; image_off -= adiff; if (image_off >= kernel_size) continue; if (size_off >= kernel_size) errx(1, "rd_root_size not in data segment"); *pmmap_off = phdr.p_offset; *pmmap_size = kernel_size; *rd_root_size_off = size_off; *rd_root_image_off = image_off; error = 0; break; } return error; } int symbol_get_u64(const char *symbol, uint64_t *result) { GElf_Sym sym; Elf_Data *data; const char *name; size_t i; int error = 1; data = NULL; while ((data = elf_rawdata(symtab, data)) != NULL) { for (i = 0; i < nsymb; i++) { if (gelf_getsym(data, i, &sym) != &sym) continue; if (sym.st_name >= strtabsz) break; if ((name = elf_strptr(e, strtabndx, sym.st_name)) == NULL) continue; if (strcmp(name, symbol) == 0) { if (result) *result = sym.st_value; error = 0; break; } } } return error; } __dead void usage(void) { extern char *__progname; fprintf(stderr, "usage: %s [-dx] bsd [fs]\n", __progname); exit(1); }