arch/i386/kernel/vsyscall-sysenter.S

   1 /*
   2  * Code for the vsyscall page.  This version uses the sysenter instruction.
   3  *
   4  * NOTE:
   5  * 1) __kernel_vsyscall _must_ be first in this page.
   6  * 2) there are alignment constraints on this stub, see vsyscall-sigreturn.S
   7  *    for details.
   8  */
   9
  10         .text
  11         .globl __kernel_vsyscall
  12         .type __kernel_vsyscall,@function
  13 __kernel_vsyscall:
  14 .LSTART_vsyscall:
  15         push %ecx
  16 .Lpush_ecx:
  17         push %edx
  18 .Lpush_edx:
  19         push %ebp
  20 .Lenter_kernel:
  21         movl %esp,%ebp
  22         sysenter
  23
  24         /* 7: align return point with nop's to make disassembly easier */
  25         .space 7,0x90
  26
  27         /* 14: System call restart point is here! (SYSENTER_RETURN - 2) */
  28         jmp .Lenter_kernel
  29         /* 16: System call normal return point is here! */
  30         .globl SYSENTER_RETURN  /* Symbol used by entry.S.  */
  31 SYSENTER_RETURN:
  32         pop %ebp
  33 .Lpop_ebp:
  34         pop %edx
  35 .Lpop_edx:
  36         pop %ecx
  37 .Lpop_ecx:
  38         ret
  39 .LEND_vsyscall:
  40         .size __kernel_vsyscall,.-.LSTART_vsyscall
  41         .previous
  42
  43         .section .eh_frame,"a",@progbits
  44 .LSTARTFRAMEDLSI:
  45         .long .LENDCIEDLSI-.LSTARTCIEDLSI
  46 .LSTARTCIEDLSI:
  47         .long 0                 /* CIE ID */
  48         .byte 1                 /* Version number */
  49         .string "zR"            /* NUL-terminated augmentation string */
  50         .uleb128 1              /* Code alignment factor */
  51         .sleb128 -4             /* Data alignment factor */
  52         .byte 8                 /* Return address register column */
  53         .uleb128 1              /* Augmentation value length */
  54         .byte 0x1b              /* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */
  55         .byte 0x0c              /* DW_CFA_def_cfa */
  56         .uleb128 4
  57         .uleb128 4
  58         .byte 0x88              /* DW_CFA_offset, column 0x8 */
  59         .uleb128 1
  60         .align 4
  61 .LENDCIEDLSI:
  62         .long .LENDFDEDLSI-.LSTARTFDEDLSI /* Length FDE */
  63 .LSTARTFDEDLSI:
  64         .long .LSTARTFDEDLSI-.LSTARTFRAMEDLSI /* CIE pointer */
  65         .long .LSTART_vsyscall-.        /* PC-relative start address */
  66         .long .LEND_vsyscall-.LSTART_vsyscall
  67         .uleb128 0
  68         /* What follows are the instructions for the table generation.
  69            We have to record all changes of the stack pointer.  */
  70         .byte 0x04              /* DW_CFA_advance_loc4 */
  71         .long .Lpush_ecx-.LSTART_vsyscall
  72         .byte 0x0e              /* DW_CFA_def_cfa_offset */
  73         .byte 0x08              /* RA at offset 8 now */
  74         .byte 0x04              /* DW_CFA_advance_loc4 */
  75         .long .Lpush_edx-.Lpush_ecx
  76         .byte 0x0e              /* DW_CFA_def_cfa_offset */
  77         .byte 0x0c              /* RA at offset 12 now */
  78         .byte 0x04              /* DW_CFA_advance_loc4 */
  79         .long .Lenter_kernel-.Lpush_edx
  80         .byte 0x0e              /* DW_CFA_def_cfa_offset */
  81         .byte 0x10              /* RA at offset 16 now */
  82         .byte 0x85, 0x04        /* DW_CFA_offset %ebp -16 */
  83         /* Finally the epilogue.  */
  84         .byte 0x04              /* DW_CFA_advance_loc4 */
  85         .long .Lpop_ebp-.Lenter_kernel
  86         .byte 0x0e              /* DW_CFA_def_cfa_offset */
  87         .byte 0x0c              /* RA at offset 12 now */
  88         .byte 0xc5              /* DW_CFA_restore %ebp */
  89         .byte 0x04              /* DW_CFA_advance_loc4 */
  90         .long .Lpop_edx-.Lpop_ebp
  91         .byte 0x0e              /* DW_CFA_def_cfa_offset */
  92         .byte 0x08              /* RA at offset 8 now */
  93         .byte 0x04              /* DW_CFA_advance_loc4 */
  94         .long .Lpop_ecx-.Lpop_edx
  95         .byte 0x0e              /* DW_CFA_def_cfa_offset */
  96         .byte 0x04              /* RA at offset 4 now */
  97         .align 4
  98 .LENDFDEDLSI:
  99         .previous
 100
 101 /*
 102  * Get the common code for the sigreturn entry points.
 103  */
 104 #include "vsyscall-sigreturn.S"