void copy_and_fixup_insn(struct insn *src_insn, void *dest,
const struct kernsym *func)
{
u32 *to_fixup;
unsigned long addr;
BUG_ON(src_insn->length == 0);
memcpy((void *)dest, (const void *)src_insn->kaddr,
src_insn->length);
if(src_insn->opcode.bytes[0] == OP_CALL_REL32 ||
src_insn->opcode.bytes[0] == OP_JMP_REL32)
{
addr = (unsigned long)CODE_ADDR_FROM_OFFSET(
src_insn->kaddr,
src_insn->length,
src_insn->immediate.value);
if(addr >= (unsigned long)func->addr &&
addr < (unsigned long)func->addr + func->size)
return;
to_fixup = (u32 *)((unsigned long)dest +
insn_offset_immediate(src_insn));
*to_fixup = CODE_OFFSET_FROM_ADDR(dest, src_insn->length,
(void *)addr);
return;
}
#ifdef CONFIG_X86_64
if(!tpe_insn_rip_relative(src_insn))
return;
addr = (unsigned long)CODE_ADDR_FROM_OFFSET(
src_insn->kaddr,
src_insn->length,
src_insn->displacement.value);
if(addr >= (unsigned long)func->addr &&
addr < (unsigned long)func->addr + func->size)
return;
to_fixup = (u32 *)((unsigned long)dest +
insn_offset_displacement(src_insn));
*to_fixup = CODE_OFFSET_FROM_ADDR(dest, src_insn->length,
(void *)addr);
#endif
return;
}
int symbol_hijack(struct kernsym *sym, const char *symbol_name, unsigned long *code) {
int ret;
unsigned long orig_addr;
unsigned long dest_addr;
unsigned long end_addr;
u32 *poffset;
struct insn insn;
bool pte_ro;
ret = find_symbol_address(sym, symbol_name);
if (IN_ERR(ret))
return ret;
if (*(u8 *)sym->addr == OP_JMP_REL32) {
printk(PKPRE "error: %s already appears to be hijacked\n", symbol_name);
return -EFAULT;
}
sym->new_addr = malloc(sym->size);
if (sym->new_addr == NULL) {
printk(PKPRE
"Failed to allocate buffer of size %lu for %s\n",
sym->size, sym->name);
return -ENOMEM;
}
memset(sym->new_addr, 0, (size_t)sym->size);
if (sym->size < OP_JMP_SIZE) {
ret = -EFAULT;
goto out_error;
}
orig_addr = (unsigned long)sym->addr;
dest_addr = (unsigned long)sym->new_addr;
end_addr = orig_addr + sym->size;
while (end_addr > orig_addr && *(u8 *)(end_addr - 1) == '\0')
--end_addr;
if (orig_addr == end_addr) {
printk(PKPRE
"A spurious symbol \"%s\" (address: %p) seems to contain only zeros\n",
sym->name,
sym->addr);
ret = -EILSEQ;
goto out_error;
}
while (orig_addr < end_addr) {
tpe_insn_init(&insn, (void *)orig_addr);
tpe_insn_get_length(&insn);
if (insn.length == 0) {
printk(PKPRE
"Failed to decode instruction at %p (%s+0x%lx)\n",
(const void *)orig_addr,
sym->name,
orig_addr - (unsigned long)sym->addr);
ret = -EILSEQ;
goto out_error;
}
copy_and_fixup_insn(&insn, (void *)dest_addr, sym);
orig_addr += insn.length;
dest_addr += insn.length;
}
sym->new_size = dest_addr - (unsigned long)sym->new_addr;
sym->run = sym->new_addr;
set_addr_rw((unsigned long) sym->addr, &pte_ro);
memcpy(&sym->orig_start_bytes[0], sym->addr, OP_JMP_SIZE);
*(u8 *)sym->addr = OP_JMP_REL32;
poffset = (u32 *)((unsigned long)sym->addr + 1);
*poffset = CODE_OFFSET_FROM_ADDR((unsigned long)sym->addr,
OP_JMP_SIZE, (unsigned long)code);
set_addr_ro((unsigned long) sym->addr, pte_ro);
sym->hijacked = true;
return 0;
out_error:
malloc_free(sym->new_addr);
return ret;
}
