Author: adrian
Date: Tue Aug 10 09:24:19 2010
New Revision: 211137
URL: http://svn.freebsd.org/changeset/base/211137
Log:
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.
Modified:
head/usr.sbin/crunch/crunchide/exec_elf32.c
Modified: head/usr.sbin/crunch/crunchide/exec_elf32.c
==============================================================================
--- head/usr.sbin/crunch/crunchide/exec_elf32.c Tue Aug 10 07:56:56 2010
(r211136)
+++ head/usr.sbin/crunch/crunchide/exec_elf32.c Tue Aug 10 09:24:19 2010
(r211137)
@@ -130,6 +130,20 @@ xmalloc(size_t size, const char *fn, con
return (rv);
}
+static void *
+xrealloc(void *ptr, size_t size, const char *fn, const char *use)
+{
+ void *rv;
+
+ rv = realloc(ptr, size);
+ if (rv == NULL) {
+ free(ptr);
+ fprintf(stderr, "%s: out of memory (reallocating for %s)\n",
+ fn, use);
+ }
+ return (rv);
+}
+
int
ELFNAMEEND(check)(int fd, const char *fn)
{
@@ -197,6 +211,21 @@ ELFNAMEEND(check)(int fd, const char *fn
return 1;
}
+/*
+ * This function 'hides' (some of) ELF executable file's symbols.
+ * It hides them by renaming them to "_$$hide$$ <filename> <symbolname>".
+ * Symbols in the global keep list, or which are marked as being undefined,
+ * are left alone.
+ *
+ * An old version of this code shuffled various tables around, turning
+ * global symbols to be hidden into local symbols. That lost on the
+ * mips, because CALL16 relocs must reference global symbols, and, if
+ * those symbols were being hidden, they were no longer global.
+ *
+ * The new renaming behaviour doesn't take global symbols out of the
+ * namespace. However, it's ... unlikely that there will ever be
+ * any collisions in practice because of the new method.
+ */
int
ELFNAMEEND(hide)(int fd, const char *fn)
{
@@ -204,11 +233,14 @@ ELFNAMEEND(hide)(int fd, const char *fn)
Elf_Shdr *shdrp = NULL, *symtabshdr, *strtabshdr;
Elf_Sym *symtabp = NULL;
char *strtabp = NULL;
- Elf_Size *symfwmap = NULL, *symrvmap = NULL, nsyms, nlocalsyms, ewi;
- struct listelem *relalist = NULL, *rellist = NULL, *tmpl;
+ Elf_Size nsyms, nlocalsyms, ewi;
ssize_t shdrsize;
int rv, i, weird;
+ size_t nstrtab_size, nstrtab_nextoff, fn_size;
+ char *nstrtabp = NULL;
unsigned char data;
+ Elf_Off maxoff, stroff;
+ const char *weirdreason = NULL;
rv = 0;
if (xreadatoff(fd, &ehdr, 0, sizeof ehdr, fn) != sizeof ehdr)
@@ -225,42 +257,38 @@ ELFNAMEEND(hide)(int fd, const char *fn)
symtabshdr = strtabshdr = NULL;
weird = 0;
+ maxoff = stroff = 0;
for (i = 0; i < xe16toh(ehdr.e_shnum); i++) {
+ if (xewtoh(shdrp[i].sh_offset) > maxoff)
+ maxoff = xewtoh(shdrp[i].sh_offset);
switch (xe32toh(shdrp[i].sh_type)) {
case SHT_SYMTAB:
if (symtabshdr != NULL)
weird = 1;
symtabshdr = &shdrp[i];
strtabshdr = &shdrp[xe32toh(shdrp[i].sh_link)];
- break;
- case SHT_RELA:
- tmpl = xmalloc(sizeof *tmpl, fn, "rela list element");
- if (tmpl == NULL)
- goto bad;
- tmpl->mem = NULL;
- tmpl->file = xewtoh(shdrp[i].sh_offset);
- tmpl->size = xewtoh(shdrp[i].sh_size);
- tmpl->next = relalist;
- relalist = tmpl;
- break;
- case SHT_REL:
- tmpl = xmalloc(sizeof *tmpl, fn, "rel list element");
- if (tmpl == NULL)
- goto bad;
- tmpl->mem = NULL;
- tmpl->file = xewtoh(shdrp[i].sh_offset);
- tmpl->size = xewtoh(shdrp[i].sh_size);
- tmpl->next = rellist;
- rellist = tmpl;
+
+ /* Check whether the string table is the last section */
+ stroff =
xewtoh(shdrp[xe32toh(shdrp[i].sh_link)].sh_offset);
+ if (!weird && xe32toh(shdrp[i].sh_link) !=
(xe16toh(ehdr.e_shnum) - 1)) {
+ weird = 1;
+ weirdreason = "string table not last section";
+ }
break;
}
}
+ if (! weirdreason)
+ weirdreason = "unsupported";
if (symtabshdr == NULL)
goto out;
if (strtabshdr == NULL)
weird = 1;
+ if (!weird && stroff != maxoff) {
+ weird = 1;
+ weirdreason = "string table section not last in file";
+ }
if (weird) {
- fprintf(stderr, "%s: weird executable (unsupported)\n", fn);
+ fprintf(stderr, "%s: weird executable (%s)\n", fn, weirdreason);
goto bad;
}
@@ -284,105 +312,53 @@ ELFNAMEEND(hide)(int fd, const char *fn)
xewtoh(strtabshdr->sh_size), fn) != xewtoh(strtabshdr->sh_size))
goto bad;
- /* any rela tables */
- for (tmpl = relalist; tmpl != NULL; tmpl = tmpl->next) {
- if ((tmpl->mem = xmalloc(tmpl->size, fn, "rela table"))
- == NULL)
- goto bad;
- if (xreadatoff(fd, tmpl->mem, tmpl->file,
- tmpl->size, fn) != tmpl->size)
- goto bad;
- }
+ nstrtab_size = 256;
+ nstrtabp = xmalloc(nstrtab_size, fn, "new string table");
+ if (nstrtabp == NULL)
+ goto bad;
+ nstrtab_nextoff = 0;
- /* any rel tables */
- for (tmpl = rellist; tmpl != NULL; tmpl = tmpl->next) {
- if ((tmpl->mem = xmalloc(tmpl->size, fn, "rel table"))
- == NULL)
- goto bad;
- if (xreadatoff(fd, tmpl->mem, tmpl->file,
- tmpl->size, fn) != tmpl->size)
- goto bad;
- }
+ fn_size = strlen(fn);
/* Prepare data structures for symbol movement. */
nsyms = xewtoh(symtabshdr->sh_size) / xewtoh(symtabshdr->sh_entsize);
nlocalsyms = xe32toh(symtabshdr->sh_info);
- if ((symfwmap = xmalloc(nsyms * sizeof (Elf_Size), fn,
- "symbol forward mapping table")) == NULL)
- goto bad;
- if ((symrvmap = xmalloc(nsyms * sizeof (Elf_Size), fn,
- "symbol reverse mapping table")) == NULL)
- goto bad;
-
- /* init location -> symbol # table */
- for (ewi = 0; ewi < nsyms; ewi++)
- symrvmap[ewi] = ewi;
/* move symbols, making them local */
- for (ewi = nlocalsyms; ewi < nsyms; ewi++) {
- Elf_Sym *sp, symswap;
- Elf_Size mapswap;
-
- sp = &symtabp[ewi];
-
- /* if it's on our keep list, don't move it */
- if (in_keep_list(strtabp + xe32toh(sp->st_name)))
- continue;
-
- /* if it's an undefined symbol, keep it */
- if (xe16toh(sp->st_shndx) == SHN_UNDEF)
- continue;
-
- /* adjust the symbol so that it's local */
- sp->st_info =
- ELF_ST_INFO(STB_LOCAL, sp->st_info);
-/* (STB_LOCAL << 4) | ELF_SYM_TYPE(sp->st_info); *//* XXX */
-
+ for (ewi = 0; ewi < nsyms; ewi++) {
+ Elf_Sym *sp = &symtabp[ewi];
+ const char *symname = strtabp + xe32toh(sp->st_name);
+ size_t newent_len;
/*
- * move the symbol to its new location
+ * make sure there's size for the next entry, even if it's
+ * as large as it can be.
+ *
+ * "_$$hide$$ <filename> <symname><NUL>" ->
+ * 9 + 3 + sizes of fn and sym name
*/
-
- /* note that symbols in those locations have been swapped */
- mapswap = symrvmap[ewi];
- symrvmap[ewi] = symrvmap[nlocalsyms];
- symrvmap[nlocalsyms] = mapswap;
-
- /* and swap the symbols */
- symswap = *sp;
- *sp = symtabp[nlocalsyms];
- symtabp[nlocalsyms] = symswap;
-
- nlocalsyms++; /* note new local sym */
- }
- symtabshdr->sh_info = htoxe32(nlocalsyms);
-
- /* set up symbol # -> location mapping table */
- for (ewi = 0; ewi < nsyms; ewi++)
- symfwmap[symrvmap[ewi]] = ewi;
-
- /* any rela tables */
- for (tmpl = relalist; tmpl != NULL; tmpl = tmpl->next) {
- Elf_Rela *relap = tmpl->mem;
-
- for (ewi = 0; ewi < tmpl->size / sizeof(*relap); ewi++) {
- relap[ewi].r_info = htoxew(ELF_R_INFO(
- symfwmap[ELF_R_SYM(xewtoh(relap[ewi].r_info))],
- ELF_R_TYPE(xewtoh(relap[ewi].r_info))
- ));
+ while ((nstrtab_size - nstrtab_nextoff) <
+ strlen(symname) + fn_size + 12) {
+ nstrtab_size *= 2;
+ nstrtabp = xrealloc(nstrtabp, nstrtab_size, fn,
+ "new string table");
+ if (nstrtabp == NULL)
+ goto bad;
}
- }
- /* any rel tables */
- for (tmpl = rellist; tmpl != NULL; tmpl = tmpl->next) {
- Elf_Rel *relp = tmpl->mem;
-
- for (ewi = 0; ewi < tmpl->size / sizeof *relp; ewi++) {
- relp[ewi].r_info = htoxew(ELF_R_INFO(
- symfwmap[ELF_R_SYM(xewtoh(relp[ewi].r_info))],
- ELF_R_TYPE(xewtoh(relp[ewi].r_info))
- ));
+ sp->st_name = htoxew(nstrtab_nextoff);
+
+ /* if it's a keeper or is undefined, don't rename it. */
+ if (in_keep_list(symname) ||
+ (xe16toh(sp->st_shndx) == SHN_UNDEF)) {
+ newent_len = sprintf(nstrtabp + nstrtab_nextoff,
+ "%s", symname) + 1;
+ } else {
+ newent_len = sprintf(nstrtabp + nstrtab_nextoff,
+ "_$$hide$$ %s %s", fn, symname) + 1;
}
+ nstrtab_nextoff += newent_len;
}
+ strtabshdr->sh_size = htoxew(nstrtab_nextoff);
/*
* write new tables to the file
@@ -393,16 +369,10 @@ ELFNAMEEND(hide)(int fd, const char *fn)
if (xwriteatoff(fd, symtabp, xewtoh(symtabshdr->sh_offset),
xewtoh(symtabshdr->sh_size), fn) != xewtoh(symtabshdr->sh_size))
goto bad;
- for (tmpl = relalist; tmpl != NULL; tmpl = tmpl->next) {
- if (xwriteatoff(fd, tmpl->mem, tmpl->file,
- tmpl->size, fn) != tmpl->size)
- goto bad;
- }
- for (tmpl = rellist; tmpl != NULL; tmpl = tmpl->next) {
- if (xwriteatoff(fd, tmpl->mem, tmpl->file,
- tmpl->size, fn) != tmpl->size)
- goto bad;
- }
+ /* write new symbol table strings */
+ if ((size_t)xwriteatoff(fd, nstrtabp, xewtoh(strtabshdr->sh_offset),
+ xewtoh(strtabshdr->sh_size), fn) != xewtoh(strtabshdr->sh_size))
+ goto bad;
out:
if (shdrp != NULL)
@@ -411,22 +381,6 @@ out:
free(symtabp);
if (strtabp != NULL)
free(strtabp);
- if (symfwmap != NULL)
- free(symfwmap);
- if (symrvmap != NULL)
- free(symrvmap);
- while ((tmpl = relalist) != NULL) {
- relalist = tmpl->next;
- if (tmpl->mem != NULL)
- free(tmpl->mem);
- free(tmpl);
- }
- while ((tmpl = rellist) != NULL) {
- rellist = tmpl->next;
- if (tmpl->mem != NULL)
- free(tmpl->mem);
- free(tmpl);
- }
return (rv);
bad:
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