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Subject[RFC -tip 2/4] x86: uaccess: introduce new __{get|put}_user exception handling framework
From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>

Impact: introduce new uaccess exception handling framework

Introduce new uaccess exception handling framework.

__{get|put}_user_ex_try() begins exception block and
__{get|put}_user_ex_catch() ends block and if an exeption occurred in this
block using __{get|put}_user_ex, thread_info->uaccess_err is set to -EFAULT
and err is set at __{get|put}_user_ex_catch().
int func()
{
int err = 0;
__get_user_ex_try();

__get_user_ex(...);
__get_user_ex(...);
:

__get_user_ex_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>
---
arch/x86/include/asm/thread_info.h | 1 +
arch/x86/include/asm/uaccess.h | 100 ++++++++++++++++++++++++++++++++++++
arch/x86/mm/extable.c | 5 ++
3 files changed, 106 insertions(+), 0 deletions(-)
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index efdf938..46beb17 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -40,6 +40,7 @@ struct thread_info {
*/
__u8 supervisor_stack[0];
#endif
+ int uaccess_err;
};

#define INIT_THREAD_INFO(tsk) \
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 1a38180..d3ac43e 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -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 +446,23 @@ 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)))
+
+#define __uaccess_ex_try() do { \
+ int __prev_err = current_thread_info()->uaccess_err; \
+ current_thread_info()->uaccess_err = 0; \
+ barrier()
+
+#define __uaccess_ex_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 +486,19 @@ struct __large_struct { unsigned long buf[100]; };

#define __get_user(x, ptr) \
__get_user_nocheck((x), (ptr), sizeof(*(ptr)))
+
+#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 __get_user_ex_try() \
+ __uaccess_ex_try()
+
+#define __get_user_ex_catch(perr) \
+ __uaccess_ex_catch(*(perr))
+
/**
* __put_user: - Write a simple value into user space, with less checking.
* @x: Value to copy to user space.
@@ -431,6 +522,15 @@ struct __large_struct { unsigned long buf[100]; };
#define __put_user(x, ptr) \
__put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))

+#define __put_user_ex(x, ptr) \
+ __put_user_size_ex((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
+
+#define __put_user_ex_try() \
+ __uaccess_ex_try()
+
+#define __put_user_ex_catch(perr) \
+ __uaccess_ex_catch(*(perr))
+
#define __get_user_unaligned __get_user
#define __put_user_unaligned __put_user

diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 7e8db53..e185e03 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -23,6 +23,11 @@ int fixup_exception(struct pt_regs *regs)

fixup = search_exception_tables(regs->ip);
if (fixup) {
+ if (fixup->fixup < 16) {
+ current_thread_info()->uaccess_err = -EFAULT;
+ regs->ip += fixup->fixup;
+ return 1;
+ }
regs->ip = fixup->fixup;
return 1;
}
--
1.6.0.4


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