Commit 44c5b676 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Peter Zijlstra
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ARM: uaccess: Implement missing __get_user_asm_dword() 



When CONFIG_CPU_SPECTRE=n then get_user() is missing the 8 byte ASM variant
for no real good reason. This prevents using get_user(u64) in generic code.

Implement it as a sequence of two 4-byte reads with LE/BE awareness and
make the unsigned long (or long long) type for the intermediate variable to
read into dependend on the the target type.

The __long_type() macro and idea was lifted from PowerPC. Thanks to
Christophe for pointing it out.

Reported-by: default avatarkernel test robot <lkp@intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202509120155.pFgwfeUD-lkp@intel.com/
Link: https://patch.msgid.link/20251027083745.168468637@linutronix.de
parent 6146a0f1

arch/arm/include/asm/uaccess.h

+25 −1
Original line number Diff line number Diff line
@@ -283,10 +283,17 @@ extern int __put_user_8(void *, unsigned long long); 
	__gu_err;							\

})



/*

 * This is a type: either unsigned long, if the argument fits into

 * that type, or otherwise unsigned long long.

 */

#define __long_type(x) \

	__typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))



#define __get_user_err(x, ptr, err, __t)				\

do {									\

	unsigned long __gu_addr = (unsigned long)(ptr);			\

	unsigned long __gu_val;						\

	__long_type(x) __gu_val;					\

	unsigned int __ua_flags;					\

	__chk_user_ptr(ptr);						\

	might_fault();							\
@@ -295,6 +302,7 @@ do { \ 
	case 1:	__get_user_asm_byte(__gu_val, __gu_addr, err, __t); break;	\

	case 2:	__get_user_asm_half(__gu_val, __gu_addr, err, __t); break;	\

	case 4:	__get_user_asm_word(__gu_val, __gu_addr, err, __t); break;	\

	case 8:	__get_user_asm_dword(__gu_val, __gu_addr, err, __t); break;	\

	default: (__gu_val) = __get_user_bad();				\

	}								\

	uaccess_restore(__ua_flags);					\
@@ -353,6 +361,22 @@ do { \ 
#define __get_user_asm_word(x, addr, err, __t)			\

	__get_user_asm(x, addr, err, "ldr" __t)



#ifdef __ARMEB__

#define __WORD0_OFFS	4

#define __WORD1_OFFS	0

#else

#define __WORD0_OFFS	0

#define __WORD1_OFFS	4

#endif



#define __get_user_asm_dword(x, addr, err, __t)				\

	({								\

	unsigned long __w0, __w1;					\

	__get_user_asm(__w0, addr + __WORD0_OFFS, err, "ldr" __t);	\

	__get_user_asm(__w1, addr + __WORD1_OFFS, err, "ldr" __t);	\

	(x) = ((u64)__w1 << 32) | (u64) __w0;				\

})



#define __put_user_switch(x, ptr, __err, __fn)				\

	do {								\

		const __typeof__(*(ptr)) __user *__pu_ptr = (ptr);	\