Recent contributions, including to DRM and binder, introduce 64-bit values in their interfaces. Common motivation example of 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:
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 9b06bb4..82b024a 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) 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) + +#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 + mov pc, lr +ENDPROC(__get_user_lo8) +#endif + +__get_user_bad8: + mov r3, #0 __get_user_bad: mov r2, #0 mov r0, #-EFAULT mov pc, 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