arch/arm/lib/clear_user.S

   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 #include <asm/unwind.h>
  13 #include <asm/export.h>
  14
  15                 .text
  16
  17 /* Prototype: unsigned long arm_clear_user(void *addr, size_t sz)
  18  * Purpose  : clear some user memory
  19  * Params   : addr - user memory address to clear
  20  *          : sz   - number of bytes to clear
  21  * Returns  : number of bytes NOT cleared
  22  */
  23 ENTRY(__clear_user_std)
  24 WEAK(arm_clear_user)
  25 UNWIND(.fnstart)
  26 UNWIND(.save {r1, lr})
  27                 stmfd   sp!, {r1, lr}
  28                 mov     r2, #0
  29                 cmp     r1, #4
  30                 blt     2f
  31                 ands    ip, r0, #3
  32                 beq     1f
  33                 cmp     ip, #2
  34                 strusr  r2, r0, 1
  35                 strusr  r2, r0, 1, le
  36                 strusr  r2, r0, 1, lt
  37                 rsb     ip, ip, #4
  38                 sub     r1, r1, ip              @  7  6  5  4  3  2  1
  39 1:              subs    r1, r1, #8              @ -1 -2 -3 -4 -5 -6 -7
  40                 strusr  r2, r0, 4, pl, rept=2
  41                 bpl     1b
  42                 adds    r1, r1, #4              @  3  2  1  0 -1 -2 -3
  43                 strusr  r2, r0, 4, pl
  44 2:              tst     r1, #2                  @ 1x 1x 0x 0x 1x 1x 0x
  45                 strusr  r2, r0, 1, ne, rept=2
  46                 tst     r1, #1                  @ x1 x0 x1 x0 x1 x0 x1
  47                 it      ne                      @ explicit IT needed for the label
  48 USER(           strnebt r2, [r0])
  49                 mov     r0, #0
  50                 ldmfd   sp!, {r1, pc}
  51 UNWIND(.fnend)
  52 ENDPROC(arm_clear_user)
  53 ENDPROC(__clear_user_std)
  54 #ifndef CONFIG_UACCESS_WITH_MEMCPY
  55 EXPORT_SYMBOL(arm_clear_user)
  56 #endif
  57
  58                 .pushsection .text.fixup,"ax"
  59                 .align  0
  60 9001:           ldmfd   sp!, {r0, pc}
  61                 .popsection
  62