crunchide(1): support non-custom elf object layout
The crunchide utility presumes the last 3 chunks of an ELF object layout are section headers, symbol table, and then string table. However, this is not specified in the ELF standards, and linkers may generate different layouts when doing partial linking (-r). This change is required to build FreeBSD with mclinker or the gold linker. PR: bin/174011 Submitted by: Pete Chou Reviewed by: Cristoph Mallon MFC after: 2 weeks
This commit is contained in:
Pedro F. Giffuni
parent
c7d346f269
commit
b5782a4705
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=246296
@ -45,6 +45,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/stat.h>
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#include <errno.h>
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#include <limits.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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@ -82,11 +83,9 @@ __FBSDID("$FreeBSD$");
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#define xe32toh(x) ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
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#define htoxe32(x) ((data == ELFDATA2MSB) ? htobe32(x) : htole32(x))
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struct listelem {
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struct listelem *next;
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void *mem;
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off_t file;
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size_t size;
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struct shlayout {
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Elf_Shdr *shdr;
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void *bufp;
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};
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static ssize_t
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@ -235,17 +234,20 @@ int
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ELFNAMEEND(hide)(int fd, const char *fn)
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{
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Elf_Ehdr ehdr;
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Elf_Shdr *shdrp = NULL, *symtabshdr, *strtabshdr;
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struct shlayout *layoutp = NULL;
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Elf_Shdr *shdrp = NULL, *symtabshdr, *strtabshdr, *shstrtabshdr;
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Elf_Shdr shdrshdr;
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Elf_Sym *symtabp = NULL;
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char *strtabp = NULL;
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Elf_Size nsyms, ewi;
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char *shstrtabp = NULL, *strtabp = NULL;
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Elf_Size nsyms, ewi;
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Elf_Off off;
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ssize_t shdrsize;
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int rv, i, weird;
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size_t nstrtab_size, nstrtab_nextoff, fn_size;
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int rv, i, weird, l, m, r, strtabidx;
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size_t nstrtab_size, nstrtab_nextoff, fn_size, size;
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char *nstrtabp = NULL;
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unsigned char data;
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Elf_Off maxoff, stroff;
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const char *weirdreason = NULL;
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void *buf;
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rv = 0;
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if (xreadatoff(fd, &ehdr, 0, sizeof ehdr, fn) != sizeof ehdr)
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@ -260,62 +262,123 @@ ELFNAMEEND(hide)(int fd, const char *fn)
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shdrsize)
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goto bad;
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symtabshdr = strtabshdr = NULL;
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symtabshdr = strtabshdr = shstrtabshdr = NULL;
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weird = 0;
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maxoff = stroff = 0;
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for (i = 0; i < xe16toh(ehdr.e_shnum); i++) {
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if (xewtoh(shdrp[i].sh_offset) > maxoff)
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maxoff = xewtoh(shdrp[i].sh_offset);
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switch (xe32toh(shdrp[i].sh_type)) {
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case SHT_SYMTAB:
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if (symtabshdr != NULL)
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if (symtabshdr != NULL) {
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weird = 1;
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weirdreason = "multiple symbol tables";
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}
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symtabshdr = &shdrp[i];
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strtabshdr = &shdrp[xe32toh(shdrp[i].sh_link)];
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/* Check whether the string table is the last section */
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stroff = xewtoh(shdrp[xe32toh(shdrp[i].sh_link)].sh_offset);
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if (!weird && xe32toh(shdrp[i].sh_link) != (xe16toh(ehdr.e_shnum) - 1)) {
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weird = 1;
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weirdreason = "string table not last section";
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}
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break;
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case SHT_STRTAB:
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if (i == xe16toh(ehdr.e_shstrndx))
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shstrtabshdr = &shdrp[i];
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break;
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}
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}
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if (! weirdreason)
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weirdreason = "unsupported";
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if (symtabshdr == NULL)
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goto out;
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if (strtabshdr == NULL)
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if (strtabshdr == NULL) {
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weird = 1;
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if (!weird && stroff != maxoff) {
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weirdreason = "string table does not exist";
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}
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if (shstrtabshdr == NULL) {
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weird = 1;
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weirdreason = "string table section not last in file";
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}
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weirdreason = "section header string table does not exist";
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}
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if (weirdreason == NULL)
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weirdreason = "unsupported";
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if (weird) {
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fprintf(stderr, "%s: weird executable (%s)\n", fn, weirdreason);
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goto bad;
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}
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/*
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* sort section layout table by offset
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*/
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layoutp = xmalloc(sizeof(struct shlayout) * (xe16toh(ehdr.e_shnum) + 1),
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fn, "layout table");
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if (layoutp == NULL)
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goto bad;
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/* add a pseudo entry to represent the section header table */
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shdrshdr.sh_offset = ehdr.e_shoff;
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shdrshdr.sh_size = htoxew(shdrsize);
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shdrshdr.sh_addralign = htoxew(ELFSIZE / 8);
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layoutp[xe16toh(ehdr.e_shnum)].shdr = &shdrshdr;
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/* insert and sort normal section headers */
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for (i = xe16toh(ehdr.e_shnum) - 1; i >= 0; i--) {
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l = i + 1;
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r = xe16toh(ehdr.e_shnum);
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while (l <= r) {
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m = ( l + r) / 2;
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if (xewtoh(shdrp[i].sh_offset) >
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xewtoh(layoutp[m].shdr->sh_offset))
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l = m + 1;
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else
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r = m - 1;
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}
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if (r != i) {
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memmove(&layoutp[i], &layoutp[i + 1],
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sizeof(struct shlayout) * (r - i));
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}
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layoutp[r].shdr = &shdrp[i];
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layoutp[r].bufp = NULL;
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}
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/*
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* load up everything we need
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*/
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/* symbol table */
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if ((symtabp = xmalloc(xewtoh(symtabshdr->sh_size), fn, "symbol table"))
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== NULL)
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/* load section string table for debug use */
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if ((shstrtabp = xmalloc(xewtoh(shstrtabshdr->sh_size), fn,
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"section string table")) == NULL)
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goto bad;
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if ((size_t)xreadatoff(fd, symtabp, xewtoh(symtabshdr->sh_offset),
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xewtoh(symtabshdr->sh_size), fn) != xewtoh(symtabshdr->sh_size))
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if ((size_t)xreadatoff(fd, shstrtabp, xewtoh(shstrtabshdr->sh_offset),
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xewtoh(shstrtabshdr->sh_size), fn) != xewtoh(shstrtabshdr->sh_size))
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goto bad;
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/* string table */
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if ((strtabp = xmalloc(xewtoh(strtabshdr->sh_size), fn, "string table"))
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== NULL)
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goto bad;
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if ((size_t)xreadatoff(fd, strtabp, xewtoh(strtabshdr->sh_offset),
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xewtoh(strtabshdr->sh_size), fn) != xewtoh(strtabshdr->sh_size))
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goto bad;
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/* we need symtab, strtab, and everything behind strtab */
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strtabidx = INT_MAX;
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for (i = 0; i < xe16toh(ehdr.e_shnum) + 1; i++) {
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if (layoutp[i].shdr == &shdrshdr) {
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/* not load section header again */
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layoutp[i].bufp = shdrp;
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continue;
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}
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if (layoutp[i].shdr == shstrtabshdr) {
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/* not load section string table again */
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layoutp[i].bufp = shstrtabp;
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continue;
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}
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if (layoutp[i].shdr == strtabshdr)
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strtabidx = i;
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if (layoutp[i].shdr == symtabshdr || i >= strtabidx) {
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off = xewtoh(layoutp[i].shdr->sh_offset);
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size = xewtoh(layoutp[i].shdr->sh_size);
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layoutp[i].bufp = xmalloc(size, fn,
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shstrtabp + xewtoh(layoutp[i].shdr->sh_name));
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if (layoutp[i].bufp == NULL)
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goto bad;
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if ((size_t)xreadatoff(fd, layoutp[i].bufp, off, size, fn) !=
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size)
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goto bad;
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/* set symbol table and string table */
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if (layoutp[i].shdr == symtabshdr)
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symtabp = layoutp[i].bufp;
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else if (layoutp[i].shdr == strtabshdr)
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strtabp = layoutp[i].bufp;
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}
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}
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nstrtab_size = 256;
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nstrtabp = xmalloc(nstrtab_size, fn, "new string table");
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@ -365,28 +428,62 @@ ELFNAMEEND(hide)(int fd, const char *fn)
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strtabshdr->sh_size = htoxew(nstrtab_nextoff);
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/*
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* write new tables to the file
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* update section header table in ascending order of offset
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*/
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if (xwriteatoff(fd, shdrp, xewtoh(ehdr.e_shoff), shdrsize, fn) !=
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shdrsize)
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goto bad;
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if ((size_t)xwriteatoff(fd, symtabp, xewtoh(symtabshdr->sh_offset),
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xewtoh(symtabshdr->sh_size), fn) != xewtoh(symtabshdr->sh_size))
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goto bad;
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/* write new symbol table strings */
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if ((size_t)xwriteatoff(fd, nstrtabp, xewtoh(strtabshdr->sh_offset),
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xewtoh(strtabshdr->sh_size), fn) != xewtoh(strtabshdr->sh_size))
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goto bad;
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for (i = strtabidx + 1; i < xe16toh(ehdr.e_shnum) + 1; i++) {
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Elf_Off off, align;
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off = xewtoh(layoutp[i - 1].shdr->sh_offset) +
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xewtoh(layoutp[i - 1].shdr->sh_size);
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align = xewtoh(layoutp[i].shdr->sh_addralign);
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off = (off + (align - 1)) & ~(align - 1);
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layoutp[i].shdr->sh_offset = htoxew(off);
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}
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/*
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* write data to the file in descending order of offset
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*/
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for (i = xe16toh(ehdr.e_shnum); i >= 0; i--) {
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if (layoutp[i].shdr == strtabshdr) {
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/* new string table */
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buf = nstrtabp;
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} else
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buf = layoutp[i].bufp;
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if (layoutp[i].shdr == &shdrshdr ||
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layoutp[i].shdr == symtabshdr || i >= strtabidx) {
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if (buf == NULL)
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goto bad;
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/*
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* update the offset of section header table in elf
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* header if needed.
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*/
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if (layoutp[i].shdr == &shdrshdr &&
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ehdr.e_shoff != shdrshdr.sh_offset) {
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ehdr.e_shoff = shdrshdr.sh_offset;
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off = (ELFSIZE == 32) ? 32 : 44;
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size = sizeof(Elf_Off);
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if ((size_t)xwriteatoff(fd, &ehdr.e_shoff, off, size,
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fn) != size)
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goto bad;
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}
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off = xewtoh(layoutp[i].shdr->sh_offset);
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size = xewtoh(layoutp[i].shdr->sh_size);
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if ((size_t)xwriteatoff(fd, buf, off, size, fn) != size)
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goto bad;
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}
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}
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out:
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if (shdrp != NULL)
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free(shdrp);
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if (symtabp != NULL)
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free(symtabp);
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if (strtabp != NULL)
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free(strtabp);
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if (nstrtabp != NULL)
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free(nstrtabp);
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if (layoutp != NULL) {
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for (i = 0; i < xe16toh(ehdr.e_shnum) + 1; i++) {
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if (layoutp[i].bufp != NULL)
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free(layoutp[i].bufp);
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}
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free(layoutp);
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}
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free(nstrtabp);
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return (rv);
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bad:
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