Commit 61a6b912 authored by Max Filippov's avatar Max Filippov
Browse files

xtensa: don't use a12 in __xtensa_copy_user in call0 ABI 



a12 is callee-saved register in xtensa call0 ABI, so a function must not
change it. The main unaligned copy loop of __xtensa_copy_user uses all
low-numbered registers, so a register must be spilled to avoid using a12
as a loop counter.

Signed-off-by: default avatarMax Filippov <jcmvbkbc@gmail.com>
parent d191323b

arch/xtensa/lib/usercopy.S

+22 −6
Original line number Diff line number Diff line
@@ -60,7 +60,12 @@ 
	.text

ENTRY(__xtensa_copy_user)



	abi_entry_default

#if !XCHAL_HAVE_LOOPS && defined(__XTENSA_CALL0_ABI__)

#define STACK_SIZE 4

#else

#define STACK_SIZE 0

#endif

	abi_entry(STACK_SIZE)

	# a2/ dst, a3/ src, a4/ len

	mov	a5, a2		# copy dst so that a2 is return value

	mov	a11, a4		# preserve original len for error case
@@ -75,7 +80,7 @@ ENTRY(__xtensa_copy_user) 
	__ssa8	a3		# set shift amount from byte offset

	bnez	a4, .Lsrcunaligned

	movi	a2, 0		# return success for len==0

	abi_ret_default

	abi_ret(STACK_SIZE)



/*

 * Destination is unaligned
@@ -127,7 +132,7 @@ EX(10f) s8i a6, a5, 0 
#endif /* !XCHAL_HAVE_LOOPS */

.Lbytecopydone:

	movi	a2, 0		# return success for len bytes copied

	abi_ret_default

	abi_ret(STACK_SIZE)



/*

 * Destination and source are word-aligned.
@@ -187,7 +192,7 @@ EX(10f) l8ui a6, a3, 0 
EX(10f)	s8i	a6, a5,  0

.L5:

	movi	a2, 0		# return success for len bytes copied

	abi_ret_default

	abi_ret(STACK_SIZE)



/*

 * Destination is aligned, Source is unaligned
@@ -205,8 +210,14 @@ EX(10f) l32i a6, a3, 0 # load first word 
	loopnez	a7, .Loop2done

#else /* !XCHAL_HAVE_LOOPS */

	beqz	a7, .Loop2done

#if defined(__XTENSA_CALL0_ABI__)

	s32i	a10, a1, 0

	slli	a10, a7, 4

	add	a10, a10, a3	# a10 = end of last 16B source chunk

#else

	slli	a12, a7, 4

	add	a12, a12, a3	# a12 = end of last 16B source chunk

#endif

#endif /* !XCHAL_HAVE_LOOPS */

.Loop2:

EX(10f)	l32i	a7, a3,  4
@@ -224,7 +235,12 @@ EX(10f) s32i a8, a5, 8 
EX(10f)	s32i	a9, a5, 12

	addi	a5, a5, 16

#if !XCHAL_HAVE_LOOPS

#if defined(__XTENSA_CALL0_ABI__)

	blt	a3, a10, .Loop2

	l32i	a10, a1, 0

#else

	blt	a3, a12, .Loop2

#endif

#endif /* !XCHAL_HAVE_LOOPS */

.Loop2done:

	bbci.l	a4, 3, .L12
@@ -264,7 +280,7 @@ EX(10f) l8ui a6, a3, 0 
EX(10f)	s8i	a6, a5,  0

.L15:

	movi	a2, 0		# return success for len bytes copied

	abi_ret_default

	abi_ret(STACK_SIZE)



ENDPROC(__xtensa_copy_user)
@@ -281,4 +297,4 @@ ENDPROC(__xtensa_copy_user) 
10:

	sub	a2, a5, a2	/* a2 <-- bytes copied */

	sub	a2, a11, a2	/* a2 <-- bytes not copied */

	abi_ret_default
 
	abi_ret(STACK_SIZE)