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Subject[PATCH 3.16.0-rc3-rmk v5] ARM: add get_user() support for 8 byte types
Date
Recent contributions, including to DRM and binder, introduce 64-bit
values in their interfaces. A common motivation for this is to allow
the same ABI for 32- and 64-bit userspaces (and therefore also a shared
ABI for 32/64 hybrid userspaces). Anyhow, the developers would like to
avoid gotchas like having to use copy_from_user().

This feature is already implemented on x86-32 and the majority of other
32-bit architectures. The current list of get_user_8 hold out
architectures are: arm, avr32, blackfin, m32r, metag, microblaze,
mn10300, sh.

Credit:

My name sits rather uneasily at the top of this patch. The v1 and
v2 versions of the patch were written by Rob Clark and to produce v4
I mostly copied code from Russell King and H. Peter Anvin. However I
have mangled the patch sufficiently that *blame* is rightfully mine
even if credit should more widely shared.

Changelog:

v5: updated to use the ret macro (requested by Russell King)
v4: remove an inlined add on big endian systems (spotted by Russell King),
used __ARMEB__ rather than BIG_ENDIAN (to match rest of file),
cleared r3 on EFAULT during __get_user_8.
v3: fix a couple of checkpatch issues
v2: pass correct size to check_uaccess, and better handling of narrowing
double word read with __get_user_xb() (Russell King's suggestion)
v1: original

Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
---
arch/arm/include/asm/uaccess.h | 20 +++++++++++++++++++-
arch/arm/lib/getuser.S | 37 ++++++++++++++++++++++++++++++++++++-
2 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 75d9579..7057cf8 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -107,6 +107,8 @@ static inline void set_fs(mm_segment_t fs)
extern int __get_user_1(void *);
extern int __get_user_2(void *);
extern int __get_user_4(void *);
+extern int __get_user_lo8(void *);
+extern int __get_user_8(void *);

#define __GUP_CLOBBER_1 "lr", "cc"
#ifdef CONFIG_CPU_USE_DOMAINS
@@ -115,6 +117,8 @@ extern int __get_user_4(void *);
#define __GUP_CLOBBER_2 "lr", "cc"
#endif
#define __GUP_CLOBBER_4 "lr", "cc"
+#define __GUP_CLOBBER_lo8 "lr", "cc"
+#define __GUP_CLOBBER_8 "lr", "cc"

#define __get_user_x(__r2,__p,__e,__l,__s) \
__asm__ __volatile__ ( \
@@ -125,11 +129,19 @@ extern int __get_user_4(void *);
: "0" (__p), "r" (__l) \
: __GUP_CLOBBER_##__s)

+/* narrowing a double-word get into a single 32bit word register: */
+#ifdef __ARMEB__
+#define __get_user_xb(__r2, __p, __e, __l, __s) \
+ __get_user_x(__r2, __p, __e, __l, lo8)
+#else
+#define __get_user_xb __get_user_x
+#endif
+
#define __get_user_check(x,p) \
({ \
unsigned long __limit = current_thread_info()->addr_limit - 1; \
register const typeof(*(p)) __user *__p asm("r0") = (p);\
- register unsigned long __r2 asm("r2"); \
+ register typeof(x) __r2 asm("r2"); \
register unsigned long __l asm("r1") = __limit; \
register int __e asm("r0"); \
switch (sizeof(*(__p))) { \
@@ -142,6 +154,12 @@ extern int __get_user_4(void *);
case 4: \
__get_user_x(__r2, __p, __e, __l, 4); \
break; \
+ case 8: \
+ if (sizeof((x)) < 8) \
+ __get_user_xb(__r2, __p, __e, __l, 4); \
+ else \
+ __get_user_x(__r2, __p, __e, __l, 8); \
+ break; \
default: __e = __get_user_bad(); break; \
} \
x = (typeof(*(p))) __r2; \
diff --git a/arch/arm/lib/getuser.S b/arch/arm/lib/getuser.S
index 0f958e3..9386000 100644
--- a/arch/arm/lib/getuser.S
+++ b/arch/arm/lib/getuser.S
@@ -18,7 +18,7 @@
* Inputs: r0 contains the address
* r1 contains the address limit, which must be preserved
* Outputs: r0 is the error code
- * r2 contains the zero-extended value
+ * r2, r3 contains the zero-extended value
* lr corrupted
*
* No other registers must be altered. (see <asm/uaccess.h>
@@ -66,15 +66,50 @@ ENTRY(__get_user_4)
ret lr
ENDPROC(__get_user_4)

+ENTRY(__get_user_8)
+ check_uaccess r0, 8, r1, r2, __get_user_bad
+#ifdef CONFIG_THUMB2_KERNEL
+5: TUSER(ldr) r2, [r0]
+6: TUSER(ldr) r3, [r0, #4]
+#else
+5: TUSER(ldr) r2, [r0], #4
+6: TUSER(ldr) r3, [r0]
+#endif
+ mov r0, #0
+ ret lr
+ENDPROC(__get_user_8)
+
+#ifdef __ARMEB__
+ENTRY(__get_user_lo8)
+ check_uaccess r0, 8, r1, r2, __get_user_bad
+#ifdef CONFIG_CPU_USE_DOMAINS
+ add r0, r0, #4
+7: ldrt r2, [r0]
+#else
+7: ldr r2, [r0, #4]
+#endif
+ mov r0, #0
+ ret lr
+ENDPROC(__get_user_lo8)
+#endif
+
+__get_user_bad8:
+ mov r3, #0
__get_user_bad:
mov r2, #0
mov r0, #-EFAULT
ret lr
ENDPROC(__get_user_bad)
+ENDPROC(__get_user_bad8)

.pushsection __ex_table, "a"
.long 1b, __get_user_bad
.long 2b, __get_user_bad
.long 3b, __get_user_bad
.long 4b, __get_user_bad
+ .long 5b, __get_user_bad8
+ .long 6b, __get_user_bad8
+#ifdef __ARMEB__
+ .long 7b, __get_user_bad
+#endif
.popsection
--
1.9.3


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