LXR linux/arch/arm/lib/clear

   1/*
   2 *  linux/arch/arm/lib/clear_user.S
   3 *
   4 *  Copyright (C) 1995, 1996,1997,1998 Russell King
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 */
  10#include <linux/linkage.h>
  11#include <asm/assembler.h>
  12
  13                .text
  14
  15/* Prototype: int __clear_user(void *addr, size_t sz)
  16 * Purpose  : clear some user memory
  17 * Params   : addr - user memory address to clear
  18 *          : sz   - number of bytes to clear
  19 * Returns  : number of bytes NOT cleared
  20 */
  21ENTRY(__clear_user_std)
  22WEAK(__clear_user)
  23                stmfd   sp!, {r1, lr}
  24                mov     r2, #0
  25                cmp     r1, #4
  26                blt     2f
  27                ands    ip, r0, #3
  28                beq     1f
  29                cmp     ip, #2
  30                strusr  r2, r0, 1
  31                strusr  r2, r0, 1, le
  32                strusr  r2, r0, 1, lt
  33                rsb     ip, ip, #4
  34                sub     r1, r1, ip              @  7  6  5  4  3  2  1
  351:              subs    r1, r1, #8              @ -1 -2 -3 -4 -5 -6 -7
  36                strusr  r2, r0, 4, pl, rept=2
  37                bpl     1b
  38                adds    r1, r1, #4              @  3  2  1  0 -1 -2 -3
  39                strusr  r2, r0, 4, pl
  402:              tst     r1, #2                  @ 1x 1x 0x 0x 1x 1x 0x
  41                strusr  r2, r0, 1, ne, rept=2
  42                tst     r1, #1                  @ x1 x0 x1 x0 x1 x0 x1
  43                it      ne                      @ explicit IT needed for the label
  44USER(           strnebt r2, [r0])
  45                mov     r0, #0
  46                ldmfd   sp!, {r1, pc}
  47ENDPROC(__clear_user)
  48ENDPROC(__clear_user_std)
  49
  50                .pushsection .fixup,"ax"
  51                .align  0
  529001:           ldmfd   sp!, {r0, pc}
  53                .popsection
  54
  55