1/* 2 * Code for the vDSO. This version uses the sysenter instruction. 3 * 4 * First get the common code for the sigreturn entry points. 5 * This must come first. 6 */ 7#include "sigreturn.S" 8 9/* 10 * The caller puts arg2 in %ecx, which gets pushed. The kernel will use 11 * %ecx itself for arg2. The pushing is because the sysexit instruction 12 * (found in entry.S) requires that we clobber %ecx with the desired %esp. 13 * User code might expect that %ecx is unclobbered though, as it would be 14 * for returning via the iret instruction, so we must push and pop. 15 * 16 * The caller puts arg3 in %edx, which the sysexit instruction requires 17 * for %eip. Thus, exactly as for arg2, we must push and pop. 18 * 19 * Arg6 is different. The caller puts arg6 in %ebp. Since the sysenter 20 * instruction clobbers %esp, the user's %esp won't even survive entry 21 * into the kernel. We store %esp in %ebp. Code in entry.S must fetch 22 * arg6 from the stack. 23 * 24 * You can not use this vsyscall for the clone() syscall because the 25 * three words on the parent stack do not get copied to the child. 26 */ 27 .text 28 .globl __kernel_vsyscall 29 .type __kernel_vsyscall,@function 30 ALIGN 31__kernel_vsyscall: 32.LSTART_vsyscall: 33 push %ecx 34.Lpush_ecx: 35 push %edx 36.Lpush_edx: 37 push %ebp 38.Lenter_kernel: 39 movl %esp,%ebp 40 sysenter 41 42 /* 7: align return point with nop's to make disassembly easier */ 43 .space 7,0x90 44 45 /* 14: System call restart point is here! (SYSENTER_RETURN-2) */ 46 int $0x80 47 /* 16: System call normal return point is here! */ 48VDSO32_SYSENTER_RETURN: /* Symbol used by sysenter.c via vdso32-syms.h */ 49 pop %ebp 50.Lpop_ebp: 51 pop %edx 52.Lpop_edx: 53 pop %ecx 54.Lpop_ecx: 55 ret 56.LEND_vsyscall: 57 .size __kernel_vsyscall,.-.LSTART_vsyscall 58 .previous 59 60 .section .eh_frame,"a",@progbits 61.LSTARTFRAMEDLSI: 62 .long .LENDCIEDLSI-.LSTARTCIEDLSI 63.LSTARTCIEDLSI: 64 .long 0 /* CIE ID */ 65 .byte 1 /* Version number */ 66 .string "zR" /* NUL-terminated augmentation string */ 67 .uleb128 1 /* Code alignment factor */ 68 .sleb128 -4 /* Data alignment factor */ 69 .byte 8 /* Return address register column */ 70 .uleb128 1 /* Augmentation value length */ 71 .byte 0x1b /* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */ 72 .byte 0x0c /* DW_CFA_def_cfa */ 73 .uleb128 4 74 .uleb128 4 75 .byte 0x88 /* DW_CFA_offset, column 0x8 */ 76 .uleb128 1 77 .align 4 78.LENDCIEDLSI: 79 .long .LENDFDEDLSI-.LSTARTFDEDLSI /* Length FDE */ 80.LSTARTFDEDLSI: 81 .long .LSTARTFDEDLSI-.LSTARTFRAMEDLSI /* CIE pointer */ 82 .long .LSTART_vsyscall-. /* PC-relative start address */ 83 .long .LEND_vsyscall-.LSTART_vsyscall 84 .uleb128 0 85 /* What follows are the instructions for the table generation. 86 We have to record all changes of the stack pointer. */ 87 .byte 0x40 + (.Lpush_ecx-.LSTART_vsyscall) /* DW_CFA_advance_loc */ 88 .byte 0x0e /* DW_CFA_def_cfa_offset */ 89 .byte 0x08 /* RA at offset 8 now */ 90 .byte 0x40 + (.Lpush_edx-.Lpush_ecx) /* DW_CFA_advance_loc */ 91 .byte 0x0e /* DW_CFA_def_cfa_offset */ 92 .byte 0x0c /* RA at offset 12 now */ 93 .byte 0x40 + (.Lenter_kernel-.Lpush_edx) /* DW_CFA_advance_loc */ 94 .byte 0x0e /* DW_CFA_def_cfa_offset */ 95 .byte 0x10 /* RA at offset 16 now */ 96 .byte 0x85, 0x04 /* DW_CFA_offset %ebp -16 */ 97 /* Finally the epilogue. */ 98 .byte 0x40 + (.Lpop_ebp-.Lenter_kernel) /* DW_CFA_advance_loc */ 99 .byte 0x0e /* DW_CFA_def_cfa_offset */ 100 .byte 0x0c /* RA at offset 12 now */ 101 .byte 0xc5 /* DW_CFA_restore %ebp */ 102 .byte 0x40 + (.Lpop_edx-.Lpop_ebp) /* DW_CFA_advance_loc */ 103 .byte 0x0e /* DW_CFA_def_cfa_offset */ 104 .byte 0x08 /* RA at offset 8 now */ 105 .byte 0x40 + (.Lpop_ecx-.Lpop_edx) /* DW_CFA_advance_loc */ 106 .byte 0x0e /* DW_CFA_def_cfa_offset */ 107 .byte 0x04 /* RA at offset 4 now */ 108 .align 4 109.LENDFDEDLSI: 110 .previous 111 112 /* 113 * Emit a symbol with the size of this .eh_frame data, 114 * to verify it matches the other versions. 115 */ 116VDSO32_vsyscall_eh_frame_size = (.LENDFDEDLSI-.LSTARTFRAMEDLSI) 117