arch/ppc64/kernel/vdso64/datapage.S

   1 /*
   2  * Access to the shared data page by the vDSO & syscall map
   3  *
   4  * Copyright (C) 2004 Benjamin Herrenschmuidt (benh@kernel.crashing.org), IBM Corp.
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/config.h>
  13 #include <asm/processor.h>
  14 #include <asm/ppc_asm.h>
  15 #include <asm/offsets.h>
  16 #include <asm/unistd.h>
  17 #include <asm/vdso.h>
  18
  19         .text
  20 V_FUNCTION_BEGIN(__get_datapage)
  21   .cfi_startproc
  22         /* We don't want that exposed or overridable as we want other objects
  23          * to be able to bl directly to here
  24          */
  25         .protected __get_datapage
  26         .hidden __get_datapage
  27
  28         mflr    r0
  29   .cfi_register lr,r0
  30
  31         bcl     20,31,1f
  32         .global __kernel_datapage_offset;
  33 __kernel_datapage_offset:
  34         .long   0
  35 1:
  36         mflr    r3
  37         mtlr    r0
  38         lwz     r0,0(r3)
  39         add     r3,r0,r3
  40         blr
  41   .cfi_endproc
  42 V_FUNCTION_END(__get_datapage)
  43
  44 /*
  45  * void *__kernel_get_syscall_map(unsigned int *syscall_count) ;
  46  *
  47  * returns a pointer to the syscall map. the map is agnostic to the
  48  * size of "long", unlike kernel bitops, it stores bits from top to
  49  * bottom so that memory actually contains a linear bitmap
  50  * check for syscall N by testing bit (0x80000000 >> (N & 0x1f)) of
  51  * 32 bits int at N >> 5.
  52  */
  53 V_FUNCTION_BEGIN(__kernel_get_syscall_map)
  54   .cfi_startproc
  55         mflr    r12
  56   .cfi_register lr,r12
  57
  58         mr      r4,r3
  59         bl      V_LOCAL_FUNC(__get_datapage)
  60         mtlr    r12
  61         addi    r3,r3,CFG_SYSCALL_MAP64
  62         cmpli   cr0,r4,0
  63         beqlr
  64         li      r0,__NR_syscalls
  65         stw     r0,0(r4)
  66         blr
  67   .cfi_endproc
  68 V_FUNCTION_END(__kernel_get_syscall_map)