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x86: uaccess: introduce try and catch framework

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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(...);
		:
	} 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>
This commit is contained in:
Hiroshi Shimamoto 2009-01-23 15:49:41 -08:00 committed by H. Peter Anvin
parent cc86c9e0dc
commit fe40c0af3c
3 changed files with 110 additions and 0 deletions
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1
arch/x86/include/asm/thread_info.h
View file

@ -40,6 +40,7 @@ struct thread_info {
*/
__u8 supervisor_stack[0];
#endif
int uaccess_err;
};
#define INIT_THREAD_INFO(tsk) \

103
arch/x86/include/asm/uaccess.h
View file

@ -199,12 +199,22 @@ extern int __get_user_bad(void);
: "=r" (err) \
: "A" (x), "r" (addr), "i" (-EFAULT), "0" (err))
#define __put_user_asm_ex_u64(x, addr) \
asm volatile("1: movl %%eax,0(%1)\n" \
"2: movl %%edx,4(%1)\n" \
"3:\n" \
_ASM_EXTABLE(1b, 2b - 1b) \
_ASM_EXTABLE(2b, 3b - 2b) \
: : "A" (x), "r" (addr))
#define __put_user_x8(x, ptr, __ret_pu) \
asm volatile("call __put_user_8" : "=a" (__ret_pu) \
: "A" ((typeof(*(ptr)))(x)), "c" (ptr) : "ebx")
#else
#define __put_user_asm_u64(x, ptr, retval) \
__put_user_asm(x, ptr, retval, "q", "", "Zr", -EFAULT)
#define __put_user_asm_ex_u64(x, addr) \
__put_user_asm_ex(x, addr, "q", "", "Zr")
#define __put_user_x8(x, ptr, __ret_pu) __put_user_x(8, x, ptr, __ret_pu)
#endif
@ -286,6 +296,27 @@ do { \
} \
} while (0)
#define __put_user_size_ex(x, ptr, size) \
do { \
__chk_user_ptr(ptr); \
switch (size) { \
case 1: \
__put_user_asm_ex(x, ptr, "b", "b", "iq"); \
break; \
case 2: \
__put_user_asm_ex(x, ptr, "w", "w", "ir"); \
break; \
case 4: \
__put_user_asm_ex(x, ptr, "l", "k", "ir"); \
break; \
case 8: \
__put_user_asm_ex_u64((__typeof__(*ptr))(x), ptr); \
break; \
default: \
__put_user_bad(); \
} \
} while (0)
#else
#define __put_user_size(x, ptr, size, retval, errret) \
@ -311,9 +342,12 @@ do { \
#ifdef CONFIG_X86_32
#define __get_user_asm_u64(x, ptr, retval, errret) (x) = __get_user_bad()
#define __get_user_asm_ex_u64(x, ptr) (x) = __get_user_bad()
#else
#define __get_user_asm_u64(x, ptr, retval, errret) \
__get_user_asm(x, ptr, retval, "q", "", "=r", errret)
#define __get_user_asm_ex_u64(x, ptr) \
__get_user_asm_ex(x, ptr, "q", "", "=r")
#endif
#define __get_user_size(x, ptr, size, retval, errret) \
@ -350,6 +384,33 @@ do { \
: "=r" (err), ltype(x) \
: "m" (__m(addr)), "i" (errret), "0" (err))
#define __get_user_size_ex(x, ptr, size) \
do { \
__chk_user_ptr(ptr); \
switch (size) { \
case 1: \
__get_user_asm_ex(x, ptr, "b", "b", "=q"); \
break; \
case 2: \
__get_user_asm_ex(x, ptr, "w", "w", "=r"); \
break; \
case 4: \
__get_user_asm_ex(x, ptr, "l", "k", "=r"); \
break; \
case 8: \
__get_user_asm_ex_u64(x, ptr); \
break; \
default: \
(x) = __get_user_bad(); \
} \
} while (0)
#define __get_user_asm_ex(x, addr, itype, rtype, ltype) \
asm volatile("1: mov"itype" %1,%"rtype"0\n" \
"2:\n" \
_ASM_EXTABLE(1b, 2b - 1b) \
: ltype(x) : "m" (__m(addr)))
#define __put_user_nocheck(x, ptr, size) \
({ \
int __pu_err; \
@ -385,6 +446,26 @@ struct __large_struct { unsigned long buf[100]; };
_ASM_EXTABLE(1b, 3b) \
: "=r"(err) \
: ltype(x), "m" (__m(addr)), "i" (errret), "0" (err))
#define __put_user_asm_ex(x, addr, itype, rtype, ltype) \
asm volatile("1: mov"itype" %"rtype"0,%1\n" \
"2:\n" \
_ASM_EXTABLE(1b, 2b - 1b) \
: : ltype(x), "m" (__m(addr)))
/*
* uaccess_try and catch
*/
#define uaccess_try do { \
int prev_err = current_thread_info()->uaccess_err; \
current_thread_info()->uaccess_err = 0; \
barrier();
#define uaccess_catch(err) \
(err) |= current_thread_info()->uaccess_err; \
current_thread_info()->uaccess_err = prev_err; \
} while (0)
/**
* __get_user: - Get a simple variable from user space, with less checking.
* @x: Variable to store result.
@ -408,6 +489,7 @@ struct __large_struct { unsigned long buf[100]; };
#define __get_user(x, ptr) \
__get_user_nocheck((x), (ptr), sizeof(*(ptr)))
/**
* __put_user: - Write a simple value into user space, with less checking.
* @x: Value to copy to user space.
@ -434,6 +516,27 @@ struct __large_struct { unsigned long buf[100]; };
#define __get_user_unaligned __get_user
#define __put_user_unaligned __put_user
/*
* {get|put}_user_try and catch
*
* get_user_try {
* get_user_ex(...);
* } get_user_catch(err)
*/
#define get_user_try uaccess_try
#define get_user_catch(err) uaccess_catch(err)
#define put_user_try uaccess_try
#define put_user_catch(err) uaccess_catch(err)
#define get_user_ex(x, ptr) do { \
unsigned long __gue_val; \
__get_user_size_ex((__gue_val), (ptr), (sizeof(*(ptr)))); \
(x) = (__force __typeof__(*(ptr)))__gue_val; \
} while (0)
#define put_user_ex(x, ptr) \
__put_user_size_ex((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
/*
* movsl can be slow when source and dest are not both 8-byte aligned
*/

6
arch/x86/mm/extable.c
View file

@ -23,6 +23,12 @@ int fixup_exception(struct pt_regs *regs)
fixup = search_exception_tables(regs->ip);
if (fixup) {
/* If fixup is less than 16, it means uaccess error */
if (fixup->fixup < 16) {
current_thread_info()->uaccess_err = -EFAULT;
regs->ip += fixup->fixup;
return 1;
}
regs->ip = fixup->fixup;
return 1;
}