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Port over changes to the crunch symbol hiding method from NetBSD.
The older symbol hiding method breaks for MIPS. This implements symbol hiding through renaming to a symbol name which is highly unlikely to clash. The NetBSD code didn't use byte-swapping macros for endian-awareness; so it didn't work when cross-compiling a MIPS world on i386/amd64. This patch includes those (as best as I could figure what they should be) and has been tested to generate valid MIPS crunch binaries both cross- and native- compiled.
This commit is contained in:
Adrian Chadd
parent
8197f57e6a
commit
7420b323a0
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=211137
@ -130,6 +130,20 @@ xmalloc(size_t size, const char *fn, const char *use)
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return (rv);
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}
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static void *
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xrealloc(void *ptr, size_t size, const char *fn, const char *use)
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{
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void *rv;
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rv = realloc(ptr, size);
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if (rv == NULL) {
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free(ptr);
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fprintf(stderr, "%s: out of memory (reallocating for %s)\n",
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fn, use);
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}
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return (rv);
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}
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int
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ELFNAMEEND(check)(int fd, const char *fn)
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{
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@ -197,6 +211,21 @@ ELFNAMEEND(check)(int fd, const char *fn)
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return 1;
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}
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/*
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* This function 'hides' (some of) ELF executable file's symbols.
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* It hides them by renaming them to "_$$hide$$ <filename> <symbolname>".
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* Symbols in the global keep list, or which are marked as being undefined,
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* are left alone.
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*
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* An old version of this code shuffled various tables around, turning
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* global symbols to be hidden into local symbols. That lost on the
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* mips, because CALL16 relocs must reference global symbols, and, if
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* those symbols were being hidden, they were no longer global.
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*
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* The new renaming behaviour doesn't take global symbols out of the
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* namespace. However, it's ... unlikely that there will ever be
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* any collisions in practice because of the new method.
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*/
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int
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ELFNAMEEND(hide)(int fd, const char *fn)
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{
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@ -204,11 +233,14 @@ ELFNAMEEND(hide)(int fd, const char *fn)
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Elf_Shdr *shdrp = NULL, *symtabshdr, *strtabshdr;
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Elf_Sym *symtabp = NULL;
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char *strtabp = NULL;
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Elf_Size *symfwmap = NULL, *symrvmap = NULL, nsyms, nlocalsyms, ewi;
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struct listelem *relalist = NULL, *rellist = NULL, *tmpl;
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Elf_Size nsyms, nlocalsyms, ewi;
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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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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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rv = 0;
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if (xreadatoff(fd, &ehdr, 0, sizeof ehdr, fn) != sizeof ehdr)
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@ -225,42 +257,38 @@ ELFNAMEEND(hide)(int fd, const char *fn)
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symtabshdr = strtabshdr = 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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weird = 1;
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symtabshdr = &shdrp[i];
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strtabshdr = &shdrp[xe32toh(shdrp[i].sh_link)];
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break;
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case SHT_RELA:
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tmpl = xmalloc(sizeof *tmpl, fn, "rela list element");
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if (tmpl == NULL)
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goto bad;
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tmpl->mem = NULL;
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tmpl->file = xewtoh(shdrp[i].sh_offset);
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tmpl->size = xewtoh(shdrp[i].sh_size);
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tmpl->next = relalist;
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relalist = tmpl;
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break;
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case SHT_REL:
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tmpl = xmalloc(sizeof *tmpl, fn, "rel list element");
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if (tmpl == NULL)
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goto bad;
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tmpl->mem = NULL;
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tmpl->file = xewtoh(shdrp[i].sh_offset);
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tmpl->size = xewtoh(shdrp[i].sh_size);
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tmpl->next = rellist;
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rellist = tmpl;
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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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}
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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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weird = 1;
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if (!weird && stroff != maxoff) {
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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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if (weird) {
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fprintf(stderr, "%s: weird executable (unsupported)\n", fn);
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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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@ -284,105 +312,53 @@ ELFNAMEEND(hide)(int fd, const char *fn)
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xewtoh(strtabshdr->sh_size), fn) != xewtoh(strtabshdr->sh_size))
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goto bad;
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/* any rela tables */
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for (tmpl = relalist; tmpl != NULL; tmpl = tmpl->next) {
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if ((tmpl->mem = xmalloc(tmpl->size, fn, "rela table"))
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== NULL)
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nstrtab_size = 256;
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nstrtabp = xmalloc(nstrtab_size, fn, "new string table");
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if (nstrtabp == NULL)
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goto bad;
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if (xreadatoff(fd, tmpl->mem, tmpl->file,
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tmpl->size, fn) != tmpl->size)
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goto bad;
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}
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nstrtab_nextoff = 0;
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/* any rel tables */
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for (tmpl = rellist; tmpl != NULL; tmpl = tmpl->next) {
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if ((tmpl->mem = xmalloc(tmpl->size, fn, "rel table"))
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== NULL)
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goto bad;
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if (xreadatoff(fd, tmpl->mem, tmpl->file,
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tmpl->size, fn) != tmpl->size)
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goto bad;
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}
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fn_size = strlen(fn);
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/* Prepare data structures for symbol movement. */
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nsyms = xewtoh(symtabshdr->sh_size) / xewtoh(symtabshdr->sh_entsize);
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nlocalsyms = xe32toh(symtabshdr->sh_info);
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if ((symfwmap = xmalloc(nsyms * sizeof (Elf_Size), fn,
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"symbol forward mapping table")) == NULL)
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goto bad;
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if ((symrvmap = xmalloc(nsyms * sizeof (Elf_Size), fn,
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"symbol reverse mapping table")) == NULL)
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goto bad;
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/* init location -> symbol # table */
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for (ewi = 0; ewi < nsyms; ewi++)
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symrvmap[ewi] = ewi;
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/* move symbols, making them local */
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for (ewi = nlocalsyms; ewi < nsyms; ewi++) {
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Elf_Sym *sp, symswap;
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Elf_Size mapswap;
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sp = &symtabp[ewi];
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/* if it's on our keep list, don't move it */
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if (in_keep_list(strtabp + xe32toh(sp->st_name)))
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continue;
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/* if it's an undefined symbol, keep it */
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if (xe16toh(sp->st_shndx) == SHN_UNDEF)
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continue;
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/* adjust the symbol so that it's local */
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sp->st_info =
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ELF_ST_INFO(STB_LOCAL, sp->st_info);
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/* (STB_LOCAL << 4) | ELF_SYM_TYPE(sp->st_info); *//* XXX */
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for (ewi = 0; ewi < nsyms; ewi++) {
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Elf_Sym *sp = &symtabp[ewi];
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const char *symname = strtabp + xe32toh(sp->st_name);
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size_t newent_len;
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/*
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* move the symbol to its new location
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* make sure there's size for the next entry, even if it's
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* as large as it can be.
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*
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* "_$$hide$$ <filename> <symname><NUL>" ->
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* 9 + 3 + sizes of fn and sym name
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*/
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/* note that symbols in those locations have been swapped */
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mapswap = symrvmap[ewi];
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symrvmap[ewi] = symrvmap[nlocalsyms];
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symrvmap[nlocalsyms] = mapswap;
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/* and swap the symbols */
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symswap = *sp;
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*sp = symtabp[nlocalsyms];
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symtabp[nlocalsyms] = symswap;
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nlocalsyms++; /* note new local sym */
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}
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symtabshdr->sh_info = htoxe32(nlocalsyms);
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/* set up symbol # -> location mapping table */
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for (ewi = 0; ewi < nsyms; ewi++)
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symfwmap[symrvmap[ewi]] = ewi;
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/* any rela tables */
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for (tmpl = relalist; tmpl != NULL; tmpl = tmpl->next) {
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Elf_Rela *relap = tmpl->mem;
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for (ewi = 0; ewi < tmpl->size / sizeof(*relap); ewi++) {
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relap[ewi].r_info = htoxew(ELF_R_INFO(
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symfwmap[ELF_R_SYM(xewtoh(relap[ewi].r_info))],
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ELF_R_TYPE(xewtoh(relap[ewi].r_info))
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));
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}
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while ((nstrtab_size - nstrtab_nextoff) <
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strlen(symname) + fn_size + 12) {
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nstrtab_size *= 2;
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nstrtabp = xrealloc(nstrtabp, nstrtab_size, fn,
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"new string table");
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if (nstrtabp == NULL)
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goto bad;
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}
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/* any rel tables */
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for (tmpl = rellist; tmpl != NULL; tmpl = tmpl->next) {
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Elf_Rel *relp = tmpl->mem;
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sp->st_name = htoxew(nstrtab_nextoff);
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for (ewi = 0; ewi < tmpl->size / sizeof *relp; ewi++) {
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relp[ewi].r_info = htoxew(ELF_R_INFO(
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symfwmap[ELF_R_SYM(xewtoh(relp[ewi].r_info))],
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ELF_R_TYPE(xewtoh(relp[ewi].r_info))
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));
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/* if it's a keeper or is undefined, don't rename it. */
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if (in_keep_list(symname) ||
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(xe16toh(sp->st_shndx) == SHN_UNDEF)) {
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newent_len = sprintf(nstrtabp + nstrtab_nextoff,
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"%s", symname) + 1;
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} else {
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newent_len = sprintf(nstrtabp + nstrtab_nextoff,
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"_$$hide$$ %s %s", fn, symname) + 1;
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}
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nstrtab_nextoff += newent_len;
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}
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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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@ -393,16 +369,10 @@ ELFNAMEEND(hide)(int fd, const char *fn)
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if (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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for (tmpl = relalist; tmpl != NULL; tmpl = tmpl->next) {
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if (xwriteatoff(fd, tmpl->mem, tmpl->file,
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tmpl->size, fn) != tmpl->size)
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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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}
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for (tmpl = rellist; tmpl != NULL; tmpl = tmpl->next) {
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if (xwriteatoff(fd, tmpl->mem, tmpl->file,
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tmpl->size, fn) != tmpl->size)
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goto bad;
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}
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out:
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if (shdrp != NULL)
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@ -411,22 +381,6 @@ ELFNAMEEND(hide)(int fd, const char *fn)
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free(symtabp);
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if (strtabp != NULL)
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free(strtabp);
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if (symfwmap != NULL)
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free(symfwmap);
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if (symrvmap != NULL)
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free(symrvmap);
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while ((tmpl = relalist) != NULL) {
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relalist = tmpl->next;
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if (tmpl->mem != NULL)
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free(tmpl->mem);
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free(tmpl);
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}
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while ((tmpl = rellist) != NULL) {
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rellist = tmpl->next;
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if (tmpl->mem != NULL)
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free(tmpl->mem);
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free(tmpl);
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}
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return (rv);
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bad:
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