linux/arch/arm/lib/csumpartialcopyuser.S
Catalin Marinas 90303b1023 [ARM] 3256/1: Make the function-returning ldm's use sp as the base register
Patch from Catalin Marinas

If the low interrupt latency mode is enabled for the CPU (from ARMv6
onwards), the ldm/stm instructions are no longer atomic. An ldm instruction
restoring the sp and pc registers can be interrupted immediately after sp
was updated but before the pc. If this happens, the CPU restores the base
register to the value before the ldm instruction but if the base register
is not sp, the interrupt routine will corrupt the stack and the restarted
ldm instruction will load garbage.

Note that future ARM cores might always run in the low interrupt latency
mode.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2006-01-12 16:53:51 +00:00

107 lines
2.3 KiB
ArmAsm

/*
* linux/arch/arm/lib/csumpartialcopyuser.S
*
* Copyright (C) 1995-1998 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.
*
* 27/03/03 Ian Molton Clean up CONFIG_CPU
*
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/errno.h>
#include <asm/asm-offsets.h>
.text
.macro save_regs
mov ip, sp
stmfd sp!, {r1 - r2, r4 - r8, fp, ip, lr, pc}
sub fp, ip, #4
.endm
.macro load_regs
ldmfd sp, {r1, r2, r4-r8, fp, sp, pc}
.endm
.macro load1b, reg1
9999: ldrbt \reg1, [r0], $1
.section __ex_table, "a"
.align 3
.long 9999b, 6001f
.previous
.endm
.macro load2b, reg1, reg2
9999: ldrbt \reg1, [r0], $1
9998: ldrbt \reg2, [r0], $1
.section __ex_table, "a"
.long 9999b, 6001f
.long 9998b, 6001f
.previous
.endm
.macro load1l, reg1
9999: ldrt \reg1, [r0], $4
.section __ex_table, "a"
.align 3
.long 9999b, 6001f
.previous
.endm
.macro load2l, reg1, reg2
9999: ldrt \reg1, [r0], $4
9998: ldrt \reg2, [r0], $4
.section __ex_table, "a"
.long 9999b, 6001f
.long 9998b, 6001f
.previous
.endm
.macro load4l, reg1, reg2, reg3, reg4
9999: ldrt \reg1, [r0], $4
9998: ldrt \reg2, [r0], $4
9997: ldrt \reg3, [r0], $4
9996: ldrt \reg4, [r0], $4
.section __ex_table, "a"
.long 9999b, 6001f
.long 9998b, 6001f
.long 9997b, 6001f
.long 9996b, 6001f
.previous
.endm
/*
* unsigned int
* csum_partial_copy_from_user(const char *src, char *dst, int len, int sum, int *err_ptr)
* r0 = src, r1 = dst, r2 = len, r3 = sum, [sp] = *err_ptr
* Returns : r0 = checksum, [[sp, #0], #0] = 0 or -EFAULT
*/
#define FN_ENTRY ENTRY(csum_partial_copy_from_user)
#include "csumpartialcopygeneric.S"
/*
* FIXME: minor buglet here
* We don't return the checksum for the data present in the buffer. To do
* so properly, we would have to add in whatever registers were loaded before
* the fault, which, with the current asm above is not predictable.
*/
.section .fixup,"ax"
.align 4
6001: mov r4, #-EFAULT
ldr r5, [fp, #4] @ *err_ptr
str r4, [r5]
ldmia sp, {r1, r2} @ retrieve dst, len
add r2, r2, r1
mov r0, #0 @ zero the buffer
6002: teq r2, r1
strneb r0, [r1], #1
bne 6002b
load_regs
.previous