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

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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: Max Filippov <jcmvbkbc@gmail.com>
This commit is contained in:
Max Filippov 2021-07-25 16:31:34 -07:00
parent d191323bc0
commit 61a6b91283
1 changed files with 22 additions and 6 deletions
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28
arch/xtensa/lib/usercopy.S
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@ -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)