On 10 July 2014 12:47, Daniel Thompson daniel.thompson@linaro.org wrote:
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"); \
Above breaks V7 BE case when get_user called for target variable of 64 bit in size but '*__p' is 32 bit or smaller. Please look at [1] for more details.
Thanks, Victor
[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-August/280806.htm...
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 valuelr 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, #0ret 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, #0ret 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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