[ARM] 2948/1: new preemption safe copy_{to|from}_user implementation

Patch from Nicolas Pitre

This patch provides a preemption safe implementation of copy_to_user
and copy_from_user based on the copy template also used for memcpy.
It is enabled unconditionally when CONFIG_PREEMPT=y.  Otherwise if the
configured architecture is not ARMv3 then it is enabled as well as it
gives better performances at least on StrongARM and XScale cores.  If
ARMv3 is not too affected or if it doesn't matter too much then
uaccess.S could be removed altogether.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 216 insertions, 2 deletions

diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index 8f9770f1af19..391f3ab3ff32 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -9,13 +9,25 @@ lib-y		:= backtrace.o changebit.o csumipv6.o csumpartial.o   \
                    copy_page.o delay.o findbit.o memchr.o memcpy.o    \
                    memmove.o memset.o memzero.o setbit.o              \
                    strncpy_from_user.o strnlen_user.o                 \
-                   strchr.o strrchr.o testchangebit.o                 \
-                   testclearbit.o testsetbit.o uaccess.o              \
+                   strchr.o strrchr.o                                 \
+                   testchangebit.o testclearbit.o testsetbit.o        \
                    getuser.o putuser.o clear_user.o                   \
                    ashldi3.o ashrdi3.o lshrdi3.o muldi3.o             \
                    ucmpdi2.o lib1funcs.o div64.o sha1.o               \
                    io-readsb.o io-writesb.o io-readsl.o io-writesl.o
 
+# the code in uaccess.S is not preemption safe and
+# probably faster on ARMv3 only
+ifeq ($CONFIG_PREEMPT,y)
+  lib-y += copy_from_user.o copy_to_user.o
+else
+ifneq ($(CONFIG_CPU_32v3),y)
+  lib-y += copy_from_user.o copy_to_user.o
+else
+  lib-y += uaccess.o
+endif
+endif
+
 ifeq ($(CONFIG_CPU_32v3),y)
   lib-y += io-readsw-armv3.o io-writesw-armv3.o
 else
diff --git a/arch/arm/lib/copy_from_user.S b/arch/arm/lib/copy_from_user.S
new file mode 100644
index 000000000000..7497393a0e81
--- /dev/null
+++ b/arch/arm/lib/copy_from_user.S
@@ -0,0 +1,101 @@
+/*
+ *  linux/arch/arm/lib/copy_from_user.S
+ *
+ *  Author:     Nicolas Pitre
+ *  Created:    Sep 29, 2005
+ *  Copyright:  MontaVista Software, Inc.
+ *
+ *  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.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+/*
+ * Prototype:
+ *
+ *      size_t __arch_copy_from_user(void *to, const void *from, size_t n)
+ *
+ * Purpose:
+ *
+ *      copy a block to kernel memory from user memory
+ *
+ * Params:
+ *
+ *      to = kernel memory
+ *      from = user memory
+ *      n = number of bytes to copy
+ *
+ * Return value:
+ *
+ *      Number of bytes NOT copied.
+ */
+
+        .macro ldr1w ptr reg abort
+100:    ldrt \reg, [\ptr], #4
+        .section __ex_table, "a"
+        .long 100b, \abort
+        .previous
+        .endm
+
+        .macro ldr4w ptr reg1 reg2 reg3 reg4 abort
+        ldr1w \ptr, \reg1, \abort
+        ldr1w \ptr, \reg2, \abort
+        ldr1w \ptr, \reg3, \abort
+        ldr1w \ptr, \reg4, \abort
+        .endm
+
+        .macro ldr8w ptr reg1 reg2 reg3 reg4 reg5 reg6 reg7 reg8 abort
+        ldr4w \ptr, \reg1, \reg2, \reg3, \reg4, \abort
+        ldr4w \ptr, \reg5, \reg6, \reg7, \reg8, \abort
+        .endm
+
+        .macro ldr1b ptr reg cond=al abort
+100:    ldr\cond\()bt \reg, [\ptr], #1
+        .section __ex_table, "a"
+        .long 100b, \abort
+        .previous
+        .endm
+
+        .macro str1w ptr reg abort
+        str \reg, [\ptr], #4
+        .endm
+
+        .macro str8w ptr reg1 reg2 reg3 reg4 reg5 reg6 reg7 reg8 abort
+        stmia \ptr!, {\reg1, \reg2, \reg3, \reg4, \reg5, \reg6, \reg7, \reg8}
+        .endm
+
+        .macro str1b ptr reg cond=al abort
+        str\cond\()b \reg, [\ptr], #1
+        .endm
+
+        .macro enter reg1 reg2
+        mov     r3, #0
+        stmdb   sp!, {r0, r2, r3, \reg1, \reg2}
+        .endm
+
+        .macro exit reg1 reg2
+        add     sp, sp, #8
+        ldmfd   sp!, {r0, \reg1, \reg2}
+        .endm
+
+        .text
+
+ENTRY(__arch_copy_from_user)
+
+#include "copy_template.S"
+
+        .section .fixup,"ax"
+        .align 0
+        copy_abort_preamble
+        ldmfd   sp!, {r1, r2}
+        sub     r3, r0, r1
+        rsb     r1, r3, r2
+        str     r1, [sp]
+        bl      __memzero
+        ldr     r0, [sp], #4
+        copy_abort_end
+        .previous
+
diff --git a/arch/arm/lib/copy_to_user.S b/arch/arm/lib/copy_to_user.S
new file mode 100644
index 000000000000..4a6d8ea14022
--- /dev/null
+++ b/arch/arm/lib/copy_to_user.S
@@ -0,0 +1,101 @@
+/*
+ *  linux/arch/arm/lib/copy_to_user.S
+ *
+ *  Author:     Nicolas Pitre
+ *  Created:    Sep 29, 2005
+ *  Copyright:  MontaVista Software, Inc.
+ *
+ *  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.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+
+/*
+ * Prototype:
+ *
+ *      size_t __arch_copy_to_user(void *to, const void *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
+ *
+ * Return value:
+ *
+ *      Number of bytes NOT copied.
+ */
+
+        .macro ldr1w ptr reg abort
+        ldr \reg, [\ptr], #4
+        .endm
+
+        .macro ldr4w ptr reg1 reg2 reg3 reg4 abort
+        ldmia \ptr!, {\reg1, \reg2, \reg3, \reg4}
+        .endm
+
+        .macro ldr8w ptr reg1 reg2 reg3 reg4 reg5 reg6 reg7 reg8 abort
+        ldmia \ptr!, {\reg1, \reg2, \reg3, \reg4, \reg5, \reg6, \reg7, \reg8}
+        .endm
+
+        .macro ldr1b ptr reg cond=al abort
+        ldr\cond\()b \reg, [\ptr], #1
+        .endm
+
+        .macro str1w ptr reg abort
+100:    strt \reg, [\ptr], #4
+        .section __ex_table, "a"
+        .long 100b, \abort
+        .previous
+        .endm
+
+        .macro str8w ptr reg1 reg2 reg3 reg4 reg5 reg6 reg7 reg8 abort
+        str1w \ptr, \reg1, \abort
+        str1w \ptr, \reg2, \abort
+        str1w \ptr, \reg3, \abort
+        str1w \ptr, \reg4, \abort
+        str1w \ptr, \reg5, \abort
+        str1w \ptr, \reg6, \abort
+        str1w \ptr, \reg7, \abort
+        str1w \ptr, \reg8, \abort
+        .endm
+
+        .macro str1b ptr reg cond=al abort
+100:    str\cond\()bt \reg, [\ptr], #1
+        .section __ex_table, "a"
+        .long 100b, \abort
+        .previous
+        .endm
+
+        .macro enter reg1 reg2
+        mov     r3, #0
+        stmdb   sp!, {r0, r2, r3, \reg1, \reg2}
+        .endm
+
+        .macro exit reg1 reg2
+        add     sp, sp, #8
+        ldmfd   sp!, {r0, \reg1, \reg2}
+        .endm
+
+        .text
+
+ENTRY(__arch_copy_to_user)
+
+#include "copy_template.S"
+
+        .section .fixup,"ax"
+        .align 0
+        copy_abort_preamble
+        ldmfd   sp!, {r1, r2, r3}
+        sub     r0, r0, r1
+        rsb     r0, r0, r2
+        copy_abort_end
+        .previous
+