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fe40c0af3c
Impact: introduce new uaccess exception handling framework
Introduce {get|put}_user_try and {get|put}_user_catch as new uaccess exception
handling framework.
{get|put}_user_try begins exception block and {get|put}_user_catch(err) ends
the block and gets err if an exception occured in {get|put}_user_ex() in the
block. The exception is stored thread_info->uaccess_err.
The example usage of this framework is below;
int func()
{
int err = 0;
get_user_try {
get_user_ex(...);
get_user_ex(...);
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} get_user_catch(err);
return err;
}
Note: get_user_ex() is not clear the value when an exception occurs, it's
different from the behavior of __get_user(), but I think it doesn't matter.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
68 lines
1.5 KiB
C
68 lines
1.5 KiB
C
#include <linux/module.h>
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#include <linux/spinlock.h>
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#include <asm/uaccess.h>
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int fixup_exception(struct pt_regs *regs)
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{
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const struct exception_table_entry *fixup;
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#ifdef CONFIG_PNPBIOS
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if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) {
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extern u32 pnp_bios_fault_eip, pnp_bios_fault_esp;
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extern u32 pnp_bios_is_utter_crap;
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pnp_bios_is_utter_crap = 1;
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printk(KERN_CRIT "PNPBIOS fault.. attempting recovery.\n");
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__asm__ volatile(
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"movl %0, %%esp\n\t"
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"jmp *%1\n\t"
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: : "g" (pnp_bios_fault_esp), "g" (pnp_bios_fault_eip));
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panic("do_trap: can't hit this");
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}
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#endif
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fixup = search_exception_tables(regs->ip);
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if (fixup) {
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/* If fixup is less than 16, it means uaccess error */
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if (fixup->fixup < 16) {
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current_thread_info()->uaccess_err = -EFAULT;
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regs->ip += fixup->fixup;
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return 1;
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}
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regs->ip = fixup->fixup;
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return 1;
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}
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return 0;
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}
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#ifdef CONFIG_X86_64
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/*
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* Need to defined our own search_extable on X86_64 to work around
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* a B stepping K8 bug.
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*/
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const struct exception_table_entry *
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search_extable(const struct exception_table_entry *first,
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const struct exception_table_entry *last,
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unsigned long value)
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{
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/* B stepping K8 bug */
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if ((value >> 32) == 0)
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value |= 0xffffffffUL << 32;
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while (first <= last) {
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const struct exception_table_entry *mid;
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long diff;
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mid = (last - first) / 2 + first;
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diff = mid->insn - value;
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if (diff == 0)
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return mid;
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else if (diff < 0)
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first = mid+1;
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else
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last = mid-1;
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}
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return NULL;
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}
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#endif
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