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authorNicolas Pitre <nicolas.pitre@linaro.org>2015-01-15 23:41:54 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2015-01-16 14:49:08 +0000
commitc25630381c6e093819d86d9618798db932cc2d90 (patch)
tree6091a27765e09308662ec19db31b653ecc2d4779 /arch/arm/lib
parent0b7857dbeb256d1a9c0c606ec4b5f417e159040b (diff)
downloadlinux-linaro-stable-c25630381c6e093819d86d9618798db932cc2d90.tar.gz
ARM: 8285/1: remove ARMv3 user access code again
This code was restored with commit 080fc66fb5 ("ARM: Bring back ARMv3 IO and user access code") because the RiscPC memory bus does not understand half-word load/stores. However only the IO code needed restoring since the alternative user access code contains no half-word accesses, is already used when CONFIG_PREEMPT is set and runs faster on a StrongARM. Signed-off-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/lib')
-rw-r--r--arch/arm/lib/Makefile15
-rw-r--r--arch/arm/lib/uaccess.S564
2 files changed, 2 insertions, 577 deletions
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index 0573faab96ad..d8a780799506 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -15,19 +15,8 @@ lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \
io-readsb.o io-writesb.o io-readsl.o io-writesl.o \
call_with_stack.o bswapsdi2.o
-mmu-y := clear_user.o copy_page.o getuser.o putuser.o
-
-# the code in uaccess.S is not preemption safe and
-# probably faster on ARMv3 only
-ifeq ($(CONFIG_PREEMPT),y)
- mmu-y += copy_from_user.o copy_to_user.o
-else
-ifneq ($(CONFIG_CPU_32v3),y)
- mmu-y += copy_from_user.o copy_to_user.o
-else
- mmu-y += uaccess.o
-endif
-endif
+mmu-y := clear_user.o copy_page.o getuser.o putuser.o \
+ copy_from_user.o copy_to_user.o
# using lib_ here won't override already available weak symbols
obj-$(CONFIG_UACCESS_WITH_MEMCPY) += uaccess_with_memcpy.o
diff --git a/arch/arm/lib/uaccess.S b/arch/arm/lib/uaccess.S
deleted file mode 100644
index e50520904b76..000000000000
--- a/arch/arm/lib/uaccess.S
+++ /dev/null
@@ -1,564 +0,0 @@
-/*
- * linux/arch/arm/lib/uaccess.S
- *
- * Copyright (C) 1995, 1996,1997,1998 Russell King
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- * Routines to block copy data to/from user memory
- * These are highly optimised both for the 4k page size
- * and for various alignments.
- */
-#include <linux/linkage.h>
-#include <asm/assembler.h>
-#include <asm/errno.h>
-#include <asm/domain.h>
-
- .text
-
-#define PAGE_SHIFT 12
-
-/* Prototype: int __copy_to_user(void *to, const char *from, size_t n)
- * Purpose : copy a block to user memory from kernel memory
- * Params : to - user memory
- * : from - kernel memory
- * : n - number of bytes to copy
- * Returns : Number of bytes NOT copied.
- */
-
-.Lc2u_dest_not_aligned:
- rsb ip, ip, #4
- cmp ip, #2
- ldrb r3, [r1], #1
-USER( TUSER( strb) r3, [r0], #1) @ May fault
- ldrgeb r3, [r1], #1
-USER( TUSER( strgeb) r3, [r0], #1) @ May fault
- ldrgtb r3, [r1], #1
-USER( TUSER( strgtb) r3, [r0], #1) @ May fault
- sub r2, r2, ip
- b .Lc2u_dest_aligned
-
-ENTRY(__copy_to_user)
- stmfd sp!, {r2, r4 - r7, lr}
- cmp r2, #4
- blt .Lc2u_not_enough
- ands ip, r0, #3
- bne .Lc2u_dest_not_aligned
-.Lc2u_dest_aligned:
-
- ands ip, r1, #3
- bne .Lc2u_src_not_aligned
-/*
- * Seeing as there has to be at least 8 bytes to copy, we can
- * copy one word, and force a user-mode page fault...
- */
-
-.Lc2u_0fupi: subs r2, r2, #4
- addmi ip, r2, #4
- bmi .Lc2u_0nowords
- ldr r3, [r1], #4
-USER( TUSER( str) r3, [r0], #4) @ May fault
- mov ip, r0, lsl #32 - PAGE_SHIFT @ On each page, use a ld/st??t instruction
- rsb ip, ip, #0
- movs ip, ip, lsr #32 - PAGE_SHIFT
- beq .Lc2u_0fupi
-/*
- * ip = max no. of bytes to copy before needing another "strt" insn
- */
- cmp r2, ip
- movlt ip, r2
- sub r2, r2, ip
- subs ip, ip, #32
- blt .Lc2u_0rem8lp
-
-.Lc2u_0cpy8lp: ldmia r1!, {r3 - r6}
- stmia r0!, {r3 - r6} @ Shouldnt fault
- ldmia r1!, {r3 - r6}
- subs ip, ip, #32
- stmia r0!, {r3 - r6} @ Shouldnt fault
- bpl .Lc2u_0cpy8lp
-
-.Lc2u_0rem8lp: cmn ip, #16
- ldmgeia r1!, {r3 - r6}
- stmgeia r0!, {r3 - r6} @ Shouldnt fault
- tst ip, #8
- ldmneia r1!, {r3 - r4}
- stmneia r0!, {r3 - r4} @ Shouldnt fault
- tst ip, #4
- ldrne r3, [r1], #4
- TUSER( strne) r3, [r0], #4 @ Shouldnt fault
- ands ip, ip, #3
- beq .Lc2u_0fupi
-.Lc2u_0nowords: teq ip, #0
- beq .Lc2u_finished
-.Lc2u_nowords: cmp ip, #2
- ldrb r3, [r1], #1
-USER( TUSER( strb) r3, [r0], #1) @ May fault
- ldrgeb r3, [r1], #1
-USER( TUSER( strgeb) r3, [r0], #1) @ May fault
- ldrgtb r3, [r1], #1
-USER( TUSER( strgtb) r3, [r0], #1) @ May fault
- b .Lc2u_finished
-
-.Lc2u_not_enough:
- movs ip, r2
- bne .Lc2u_nowords
-.Lc2u_finished: mov r0, #0
- ldmfd sp!, {r2, r4 - r7, pc}
-
-.Lc2u_src_not_aligned:
- bic r1, r1, #3
- ldr r7, [r1], #4
- cmp ip, #2
- bgt .Lc2u_3fupi
- beq .Lc2u_2fupi
-.Lc2u_1fupi: subs r2, r2, #4
- addmi ip, r2, #4
- bmi .Lc2u_1nowords
- mov r3, r7, lspull #8
- ldr r7, [r1], #4
- orr r3, r3, r7, lspush #24
-USER( TUSER( str) r3, [r0], #4) @ May fault
- mov ip, r0, lsl #32 - PAGE_SHIFT
- rsb ip, ip, #0
- movs ip, ip, lsr #32 - PAGE_SHIFT
- beq .Lc2u_1fupi
- cmp r2, ip
- movlt ip, r2
- sub r2, r2, ip
- subs ip, ip, #16
- blt .Lc2u_1rem8lp
-
-.Lc2u_1cpy8lp: mov r3, r7, lspull #8
- ldmia r1!, {r4 - r7}
- subs ip, ip, #16
- orr r3, r3, r4, lspush #24
- mov r4, r4, lspull #8
- orr r4, r4, r5, lspush #24
- mov r5, r5, lspull #8
- orr r5, r5, r6, lspush #24
- mov r6, r6, lspull #8
- orr r6, r6, r7, lspush #24
- stmia r0!, {r3 - r6} @ Shouldnt fault
- bpl .Lc2u_1cpy8lp
-
-.Lc2u_1rem8lp: tst ip, #8
- movne r3, r7, lspull #8
- ldmneia r1!, {r4, r7}
- orrne r3, r3, r4, lspush #24
- movne r4, r4, lspull #8
- orrne r4, r4, r7, lspush #24
- stmneia r0!, {r3 - r4} @ Shouldnt fault
- tst ip, #4
- movne r3, r7, lspull #8
- ldrne r7, [r1], #4
- orrne r3, r3, r7, lspush #24
- TUSER( strne) r3, [r0], #4 @ Shouldnt fault
- ands ip, ip, #3
- beq .Lc2u_1fupi
-.Lc2u_1nowords: mov r3, r7, get_byte_1
- teq ip, #0
- beq .Lc2u_finished
- cmp ip, #2
-USER( TUSER( strb) r3, [r0], #1) @ May fault
- movge r3, r7, get_byte_2
-USER( TUSER( strgeb) r3, [r0], #1) @ May fault
- movgt r3, r7, get_byte_3
-USER( TUSER( strgtb) r3, [r0], #1) @ May fault
- b .Lc2u_finished
-
-.Lc2u_2fupi: subs r2, r2, #4
- addmi ip, r2, #4
- bmi .Lc2u_2nowords
- mov r3, r7, lspull #16
- ldr r7, [r1], #4
- orr r3, r3, r7, lspush #16
-USER( TUSER( str) r3, [r0], #4) @ May fault
- mov ip, r0, lsl #32 - PAGE_SHIFT
- rsb ip, ip, #0
- movs ip, ip, lsr #32 - PAGE_SHIFT
- beq .Lc2u_2fupi
- cmp r2, ip
- movlt ip, r2
- sub r2, r2, ip
- subs ip, ip, #16
- blt .Lc2u_2rem8lp
-
-.Lc2u_2cpy8lp: mov r3, r7, lspull #16
- ldmia r1!, {r4 - r7}
- subs ip, ip, #16
- orr r3, r3, r4, lspush #16
- mov r4, r4, lspull #16
- orr r4, r4, r5, lspush #16
- mov r5, r5, lspull #16
- orr r5, r5, r6, lspush #16
- mov r6, r6, lspull #16
- orr r6, r6, r7, lspush #16
- stmia r0!, {r3 - r6} @ Shouldnt fault
- bpl .Lc2u_2cpy8lp
-
-.Lc2u_2rem8lp: tst ip, #8
- movne r3, r7, lspull #16
- ldmneia r1!, {r4, r7}
- orrne r3, r3, r4, lspush #16
- movne r4, r4, lspull #16
- orrne r4, r4, r7, lspush #16
- stmneia r0!, {r3 - r4} @ Shouldnt fault
- tst ip, #4
- movne r3, r7, lspull #16
- ldrne r7, [r1], #4
- orrne r3, r3, r7, lspush #16
- TUSER( strne) r3, [r0], #4 @ Shouldnt fault
- ands ip, ip, #3
- beq .Lc2u_2fupi
-.Lc2u_2nowords: mov r3, r7, get_byte_2
- teq ip, #0
- beq .Lc2u_finished
- cmp ip, #2
-USER( TUSER( strb) r3, [r0], #1) @ May fault
- movge r3, r7, get_byte_3
-USER( TUSER( strgeb) r3, [r0], #1) @ May fault
- ldrgtb r3, [r1], #0
-USER( TUSER( strgtb) r3, [r0], #1) @ May fault
- b .Lc2u_finished
-
-.Lc2u_3fupi: subs r2, r2, #4
- addmi ip, r2, #4
- bmi .Lc2u_3nowords
- mov r3, r7, lspull #24
- ldr r7, [r1], #4
- orr r3, r3, r7, lspush #8
-USER( TUSER( str) r3, [r0], #4) @ May fault
- mov ip, r0, lsl #32 - PAGE_SHIFT
- rsb ip, ip, #0
- movs ip, ip, lsr #32 - PAGE_SHIFT
- beq .Lc2u_3fupi
- cmp r2, ip
- movlt ip, r2
- sub r2, r2, ip
- subs ip, ip, #16
- blt .Lc2u_3rem8lp
-
-.Lc2u_3cpy8lp: mov r3, r7, lspull #24
- ldmia r1!, {r4 - r7}
- subs ip, ip, #16
- orr r3, r3, r4, lspush #8
- mov r4, r4, lspull #24
- orr r4, r4, r5, lspush #8
- mov r5, r5, lspull #24
- orr r5, r5, r6, lspush #8
- mov r6, r6, lspull #24
- orr r6, r6, r7, lspush #8
- stmia r0!, {r3 - r6} @ Shouldnt fault
- bpl .Lc2u_3cpy8lp
-
-.Lc2u_3rem8lp: tst ip, #8
- movne r3, r7, lspull #24
- ldmneia r1!, {r4, r7}
- orrne r3, r3, r4, lspush #8
- movne r4, r4, lspull #24
- orrne r4, r4, r7, lspush #8
- stmneia r0!, {r3 - r4} @ Shouldnt fault
- tst ip, #4
- movne r3, r7, lspull #24
- ldrne r7, [r1], #4
- orrne r3, r3, r7, lspush #8
- TUSER( strne) r3, [r0], #4 @ Shouldnt fault
- ands ip, ip, #3
- beq .Lc2u_3fupi
-.Lc2u_3nowords: mov r3, r7, get_byte_3
- teq ip, #0
- beq .Lc2u_finished
- cmp ip, #2
-USER( TUSER( strb) r3, [r0], #1) @ May fault
- ldrgeb r3, [r1], #1
-USER( TUSER( strgeb) r3, [r0], #1) @ May fault
- ldrgtb r3, [r1], #0
-USER( TUSER( strgtb) r3, [r0], #1) @ May fault
- b .Lc2u_finished
-ENDPROC(__copy_to_user)
-
- .pushsection .fixup,"ax"
- .align 0
-9001: ldmfd sp!, {r0, r4 - r7, pc}
- .popsection
-
-/* Prototype: unsigned long __copy_from_user(void *to,const void *from,unsigned long n);
- * Purpose : copy a block from user memory to kernel memory
- * Params : to - kernel memory
- * : from - user memory
- * : n - number of bytes to copy
- * Returns : Number of bytes NOT copied.
- */
-.Lcfu_dest_not_aligned:
- rsb ip, ip, #4
- cmp ip, #2
-USER( TUSER( ldrb) r3, [r1], #1) @ May fault
- strb r3, [r0], #1
-USER( TUSER( ldrgeb) r3, [r1], #1) @ May fault
- strgeb r3, [r0], #1
-USER( TUSER( ldrgtb) r3, [r1], #1) @ May fault
- strgtb r3, [r0], #1
- sub r2, r2, ip
- b .Lcfu_dest_aligned
-
-ENTRY(__copy_from_user)
- stmfd sp!, {r0, r2, r4 - r7, lr}
- cmp r2, #4
- blt .Lcfu_not_enough
- ands ip, r0, #3
- bne .Lcfu_dest_not_aligned
-.Lcfu_dest_aligned:
- ands ip, r1, #3
- bne .Lcfu_src_not_aligned
-
-/*
- * Seeing as there has to be at least 8 bytes to copy, we can
- * copy one word, and force a user-mode page fault...
- */
-
-.Lcfu_0fupi: subs r2, r2, #4
- addmi ip, r2, #4
- bmi .Lcfu_0nowords
-USER( TUSER( ldr) r3, [r1], #4)
- str r3, [r0], #4
- mov ip, r1, lsl #32 - PAGE_SHIFT @ On each page, use a ld/st??t instruction
- rsb ip, ip, #0
- movs ip, ip, lsr #32 - PAGE_SHIFT
- beq .Lcfu_0fupi
-/*
- * ip = max no. of bytes to copy before needing another "strt" insn
- */
- cmp r2, ip
- movlt ip, r2
- sub r2, r2, ip
- subs ip, ip, #32
- blt .Lcfu_0rem8lp
-
-.Lcfu_0cpy8lp: ldmia r1!, {r3 - r6} @ Shouldnt fault
- stmia r0!, {r3 - r6}
- ldmia r1!, {r3 - r6} @ Shouldnt fault
- subs ip, ip, #32
- stmia r0!, {r3 - r6}
- bpl .Lcfu_0cpy8lp
-
-.Lcfu_0rem8lp: cmn ip, #16
- ldmgeia r1!, {r3 - r6} @ Shouldnt fault
- stmgeia r0!, {r3 - r6}
- tst ip, #8
- ldmneia r1!, {r3 - r4} @ Shouldnt fault
- stmneia r0!, {r3 - r4}
- tst ip, #4
- TUSER( ldrne) r3, [r1], #4 @ Shouldnt fault
- strne r3, [r0], #4
- ands ip, ip, #3
- beq .Lcfu_0fupi
-.Lcfu_0nowords: teq ip, #0
- beq .Lcfu_finished
-.Lcfu_nowords: cmp ip, #2
-USER( TUSER( ldrb) r3, [r1], #1) @ May fault
- strb r3, [r0], #1
-USER( TUSER( ldrgeb) r3, [r1], #1) @ May fault
- strgeb r3, [r0], #1
-USER( TUSER( ldrgtb) r3, [r1], #1) @ May fault
- strgtb r3, [r0], #1
- b .Lcfu_finished
-
-.Lcfu_not_enough:
- movs ip, r2
- bne .Lcfu_nowords
-.Lcfu_finished: mov r0, #0
- add sp, sp, #8
- ldmfd sp!, {r4 - r7, pc}
-
-.Lcfu_src_not_aligned:
- bic r1, r1, #3
-USER( TUSER( ldr) r7, [r1], #4) @ May fault
- cmp ip, #2
- bgt .Lcfu_3fupi
- beq .Lcfu_2fupi
-.Lcfu_1fupi: subs r2, r2, #4
- addmi ip, r2, #4
- bmi .Lcfu_1nowords
- mov r3, r7, lspull #8
-USER( TUSER( ldr) r7, [r1], #4) @ May fault
- orr r3, r3, r7, lspush #24
- str r3, [r0], #4
- mov ip, r1, lsl #32 - PAGE_SHIFT
- rsb ip, ip, #0
- movs ip, ip, lsr #32 - PAGE_SHIFT
- beq .Lcfu_1fupi
- cmp r2, ip
- movlt ip, r2
- sub r2, r2, ip
- subs ip, ip, #16
- blt .Lcfu_1rem8lp
-
-.Lcfu_1cpy8lp: mov r3, r7, lspull #8
- ldmia r1!, {r4 - r7} @ Shouldnt fault
- subs ip, ip, #16
- orr r3, r3, r4, lspush #24
- mov r4, r4, lspull #8
- orr r4, r4, r5, lspush #24
- mov r5, r5, lspull #8
- orr r5, r5, r6, lspush #24
- mov r6, r6, lspull #8
- orr r6, r6, r7, lspush #24
- stmia r0!, {r3 - r6}
- bpl .Lcfu_1cpy8lp
-
-.Lcfu_1rem8lp: tst ip, #8
- movne r3, r7, lspull #8
- ldmneia r1!, {r4, r7} @ Shouldnt fault
- orrne r3, r3, r4, lspush #24
- movne r4, r4, lspull #8
- orrne r4, r4, r7, lspush #24
- stmneia r0!, {r3 - r4}
- tst ip, #4
- movne r3, r7, lspull #8
-USER( TUSER( ldrne) r7, [r1], #4) @ May fault
- orrne r3, r3, r7, lspush #24
- strne r3, [r0], #4
- ands ip, ip, #3
- beq .Lcfu_1fupi
-.Lcfu_1nowords: mov r3, r7, get_byte_1
- teq ip, #0
- beq .Lcfu_finished
- cmp ip, #2
- strb r3, [r0], #1
- movge r3, r7, get_byte_2
- strgeb r3, [r0], #1
- movgt r3, r7, get_byte_3
- strgtb r3, [r0], #1
- b .Lcfu_finished
-
-.Lcfu_2fupi: subs r2, r2, #4
- addmi ip, r2, #4
- bmi .Lcfu_2nowords
- mov r3, r7, lspull #16
-USER( TUSER( ldr) r7, [r1], #4) @ May fault
- orr r3, r3, r7, lspush #16
- str r3, [r0], #4
- mov ip, r1, lsl #32 - PAGE_SHIFT
- rsb ip, ip, #0
- movs ip, ip, lsr #32 - PAGE_SHIFT
- beq .Lcfu_2fupi
- cmp r2, ip
- movlt ip, r2
- sub r2, r2, ip
- subs ip, ip, #16
- blt .Lcfu_2rem8lp
-
-
-.Lcfu_2cpy8lp: mov r3, r7, lspull #16
- ldmia r1!, {r4 - r7} @ Shouldnt fault
- subs ip, ip, #16
- orr r3, r3, r4, lspush #16
- mov r4, r4, lspull #16
- orr r4, r4, r5, lspush #16
- mov r5, r5, lspull #16
- orr r5, r5, r6, lspush #16
- mov r6, r6, lspull #16
- orr r6, r6, r7, lspush #16
- stmia r0!, {r3 - r6}
- bpl .Lcfu_2cpy8lp
-
-.Lcfu_2rem8lp: tst ip, #8
- movne r3, r7, lspull #16
- ldmneia r1!, {r4, r7} @ Shouldnt fault
- orrne r3, r3, r4, lspush #16
- movne r4, r4, lspull #16
- orrne r4, r4, r7, lspush #16
- stmneia r0!, {r3 - r4}
- tst ip, #4
- movne r3, r7, lspull #16
-USER( TUSER( ldrne) r7, [r1], #4) @ May fault
- orrne r3, r3, r7, lspush #16
- strne r3, [r0], #4
- ands ip, ip, #3
- beq .Lcfu_2fupi
-.Lcfu_2nowords: mov r3, r7, get_byte_2
- teq ip, #0
- beq .Lcfu_finished
- cmp ip, #2
- strb r3, [r0], #1
- movge r3, r7, get_byte_3
- strgeb r3, [r0], #1
-USER( TUSER( ldrgtb) r3, [r1], #0) @ May fault
- strgtb r3, [r0], #1
- b .Lcfu_finished
-
-.Lcfu_3fupi: subs r2, r2, #4
- addmi ip, r2, #4
- bmi .Lcfu_3nowords
- mov r3, r7, lspull #24
-USER( TUSER( ldr) r7, [r1], #4) @ May fault
- orr r3, r3, r7, lspush #8
- str r3, [r0], #4
- mov ip, r1, lsl #32 - PAGE_SHIFT
- rsb ip, ip, #0
- movs ip, ip, lsr #32 - PAGE_SHIFT
- beq .Lcfu_3fupi
- cmp r2, ip
- movlt ip, r2
- sub r2, r2, ip
- subs ip, ip, #16
- blt .Lcfu_3rem8lp
-
-.Lcfu_3cpy8lp: mov r3, r7, lspull #24
- ldmia r1!, {r4 - r7} @ Shouldnt fault
- orr r3, r3, r4, lspush #8
- mov r4, r4, lspull #24
- orr r4, r4, r5, lspush #8
- mov r5, r5, lspull #24
- orr r5, r5, r6, lspush #8
- mov r6, r6, lspull #24
- orr r6, r6, r7, lspush #8
- stmia r0!, {r3 - r6}
- subs ip, ip, #16
- bpl .Lcfu_3cpy8lp
-
-.Lcfu_3rem8lp: tst ip, #8
- movne r3, r7, lspull #24
- ldmneia r1!, {r4, r7} @ Shouldnt fault
- orrne r3, r3, r4, lspush #8
- movne r4, r4, lspull #24
- orrne r4, r4, r7, lspush #8
- stmneia r0!, {r3 - r4}
- tst ip, #4
- movne r3, r7, lspull #24
-USER( TUSER( ldrne) r7, [r1], #4) @ May fault
- orrne r3, r3, r7, lspush #8
- strne r3, [r0], #4
- ands ip, ip, #3
- beq .Lcfu_3fupi
-.Lcfu_3nowords: mov r3, r7, get_byte_3
- teq ip, #0
- beq .Lcfu_finished
- cmp ip, #2
- strb r3, [r0], #1
-USER( TUSER( ldrgeb) r3, [r1], #1) @ May fault
- strgeb r3, [r0], #1
-USER( TUSER( ldrgtb) r3, [r1], #1) @ May fault
- strgtb r3, [r0], #1
- b .Lcfu_finished
-ENDPROC(__copy_from_user)
-
- .pushsection .fixup,"ax"
- .align 0
- /*
- * We took an exception. r0 contains a pointer to
- * the byte not copied.
- */
-9001: ldr r2, [sp], #4 @ void *to
- sub r2, r0, r2 @ bytes copied
- ldr r1, [sp], #4 @ unsigned long count
- subs r4, r1, r2 @ bytes left to copy
- movne r1, r4
- blne __memzero
- mov r0, r4
- ldmfd sp!, {r4 - r7, pc}
- .popsection
-