extable.c
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#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/sort.h>
#include <asm/uaccess.h>
static inline unsigned long
ex_insn_addr(const struct exception_table_entry *x)
{
return (unsigned long)&x->insn + x->insn;
}
static inline unsigned long
ex_fixup_addr(const struct exception_table_entry *x)
{
return (unsigned long)&x->fixup + x->fixup;
}
int fixup_exception(struct pt_regs *regs)
{
const struct exception_table_entry *fixup;
unsigned long new_ip;
#ifdef CONFIG_PNPBIOS
if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) {
extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp;
extern u32 pnp_bios_is_utter_crap;
pnp_bios_is_utter_crap = 1;
printk(KERN_CRIT "PNPBIOS fault.. attempting recovery.\n");
__asm__ volatile(
"movl %0, %%esp\n\t"
"jmp *%1\n\t"
: : "g" (pnp_bios_fault_esp), "g" (pnp_bios_fault_eip));
panic("do_trap: can't hit this");
}
#endif
fixup = search_exception_tables(regs->ip);
if (fixup) {
new_ip = ex_fixup_addr(fixup);
if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
/* Special hack for uaccess_err */
current_thread_info()->uaccess_err = 1;
new_ip -= 0x7ffffff0;
}
regs->ip = new_ip;
return 1;
}
return 0;
}
/* Restricted version used during very early boot */
int __init early_fixup_exception(unsigned long *ip)
{
const struct exception_table_entry *fixup;
unsigned long new_ip;
fixup = search_exception_tables(*ip);
if (fixup) {
new_ip = ex_fixup_addr(fixup);
if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
/* uaccess handling not supported during early boot */
return 0;
}
*ip = new_ip;
return 1;
}
return 0;
}
/*
* Search one exception table for an entry corresponding to the
* given instruction address, and return the address of the entry,
* or NULL if none is found.
* We use a binary search, and thus we assume that the table is
* already sorted.
*/
const struct exception_table_entry *
search_extable(const struct exception_table_entry *first,
const struct exception_table_entry *last,
unsigned long value)
{
while (first <= last) {
const struct exception_table_entry *mid;
unsigned long addr;
mid = ((last - first) >> 1) + first;
addr = ex_insn_addr(mid);
if (addr < value)
first = mid + 1;
else if (addr > value)
last = mid - 1;
else
return mid;
}
return NULL;
}
/*
* The exception table needs to be sorted so that the binary
* search that we use to find entries in it works properly.
* This is used both for the kernel exception table and for
* the exception tables of modules that get loaded.
*
*/
static int cmp_ex(const void *a, const void *b)
{
const struct exception_table_entry *x = a, *y = b;
/*
* This value will always end up fittin in an int, because on
* both i386 and x86-64 the kernel symbol-reachable address
* space is < 2 GiB.
*
* This compare is only valid after normalization.
*/
return x->insn - y->insn;
}
void sort_extable(struct exception_table_entry *start,
struct exception_table_entry *finish)
{
struct exception_table_entry *p;
int i;
/* Convert all entries to being relative to the start of the section */
i = 0;
for (p = start; p < finish; p++) {
p->insn += i;
i += 4;
p->fixup += i;
i += 4;
}
sort(start, finish - start, sizeof(struct exception_table_entry),
cmp_ex, NULL);
/* Denormalize all entries */
i = 0;
for (p = start; p < finish; p++) {
p->insn -= i;
i += 4;
p->fixup -= i;
i += 4;
}
}
#ifdef CONFIG_MODULES
/*
* If the exception table is sorted, any referring to the module init
* will be at the beginning or the end.
*/
void trim_init_extable(struct module *m)
{
/*trim the beginning*/
while (m->num_exentries &&
within_module_init(ex_insn_addr(&m->extable[0]), m)) {
m->extable++;
m->num_exentries--;
}
/*trim the end*/
while (m->num_exentries &&
within_module_init(ex_insn_addr(&m->extable[m->num_exentries-1]), m))
m->num_exentries--;
}
#endif /* CONFIG_MODULES */