lkml.org 
[lkml]   [2014]   [Jun]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v3] ARM: add get_user() support for 8 byte types
Date
A new atomic modeset/pageflip ioctl being developed in DRM requires
get_user() to work for 64bit types (in addition to just put_user()).

v1: original
v2: pass correct size to check_uaccess, and better handling of narrowing
double word read with __get_user_xb() (Russell King's suggestion)
v3: fix a couple of checkpatch issues

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>
---

Notes:
I'd like to wake this patch up again. It was rejected back in 2012 on
the grounds that other architectures (notably x86-32) didn't implement
this so adding for ARM risked portability problems in drivers. However
shortly after the discussion (in fact I believe that as a *result* of
that discussion) support for 64-bit get_user() was added for x86-32.

A quick review of different architectures uaccess.h shows that ARM is
in the minority (even after excluding 64-bit architectures) in not
implementing this feature.

The reasons to wake it up are the same as before. Recent contributions,
including to DRM[1] and binder[2] would prefer to use the 64-bit values
in their interfaces without gotchas like having to use copy_from_user().

[1] http://thread.gmane.org/gmane.comp.video.dri.devel/102135/focus=102149
[2] http://thread.gmane.org/gmane.linux.kernel/1653448/focus=1653449

arch/arm/include/asm/uaccess.h | 18 +++++++++++++++++-
arch/arm/lib/getuser.S | 17 ++++++++++++++++-
2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 75d9579..5f7db3fb 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -107,6 +107,7 @@ 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_8(void *);

#define __GUP_CLOBBER_1 "lr", "cc"
#ifdef CONFIG_CPU_USE_DOMAINS
@@ -115,6 +116,7 @@ extern int __get_user_4(void *);
#define __GUP_CLOBBER_2 "lr", "cc"
#endif
#define __GUP_CLOBBER_4 "lr", "cc"
+#define __GUP_CLOBBER_8 "lr", "cc"

#define __get_user_x(__r2,__p,__e,__l,__s) \
__asm__ __volatile__ ( \
@@ -125,11 +127,19 @@ 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 BIG_ENDIAN
+#define __get_user_xb(__r2, __p, __e, __l, __s) \
+ __get_user_x(__r2, (uintptr_t)__p + 4, __e, __l, __s)
+#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 +152,12 @@ 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 9b06bb4..ed98707 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>
@@ -66,6 +66,19 @@ ENTRY(__get_user_4)
mov pc, 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
+ mov pc, lr
+ENDPROC(__get_user_8)
+
__get_user_bad:
mov r2, #0
mov r0, #-EFAULT
@@ -77,4 +90,6 @@ ENDPROC(__get_user_bad)
.long 2b, __get_user_bad
.long 3b, __get_user_bad
.long 4b, __get_user_bad
+ .long 5b, __get_user_bad
+ .long 6b, __get_user_bad
.popsection
--
1.9.3


\
 
 \ /
  Last update: 2014-06-12 18:21    [W:0.074 / U:5.908 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site