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- /*
- * Code for the vsyscall page. This version uses the sysenter instruction.
- *
- * NOTE:
- * 1) __kernel_vsyscall _must_ be first in this page.
- * 2) there are alignment constraints on this stub, see vsyscall-sigreturn.S
- * for details.
- */
- /*
- * The caller puts arg2 in %ecx, which gets pushed. The kernel will use
- * %ecx itself for arg2. The pushing is because the sysexit instruction
- * (found in entry.S) requires that we clobber %ecx with the desired %esp.
- * User code might expect that %ecx is unclobbered though, as it would be
- * for returning via the iret instruction, so we must push and pop.
- *
- * The caller puts arg3 in %edx, which the sysexit instruction requires
- * for %eip. Thus, exactly as for arg2, we must push and pop.
- *
- * Arg6 is different. The caller puts arg6 in %ebp. Since the sysenter
- * instruction clobbers %esp, the user's %esp won't even survive entry
- * into the kernel. We store %esp in %ebp. Code in entry.S must fetch
- * arg6 from the stack.
- */
- .text
- .globl __kernel_vsyscall
- .type __kernel_vsyscall,@function
- __kernel_vsyscall:
- .LSTART_vsyscall:
- push %ecx
- .Lpush_ecx:
- push %edx
- .Lpush_edx:
- push %ebp
- .Lenter_kernel:
- movl %esp,%ebp
- sysenter
- /* 7: align return point with nop's to make disassembly easier */
- .space 7,0x90
- /* 14: System call restart point is here! (SYSENTER_RETURN - 2) */
- jmp .Lenter_kernel
- /* 16: System call normal return point is here! */
- .globl SYSENTER_RETURN /* Symbol used by entry.S. */
- SYSENTER_RETURN:
- pop %ebp
- .Lpop_ebp:
- pop %edx
- .Lpop_edx:
- pop %ecx
- .Lpop_ecx:
- ret
- .LEND_vsyscall:
- .size __kernel_vsyscall,.-.LSTART_vsyscall
- .previous
- .section .eh_frame,"a",@progbits
- .LSTARTFRAMEDLSI:
- .long .LENDCIEDLSI-.LSTARTCIEDLSI
- .LSTARTCIEDLSI:
- .long 0 /* CIE ID */
- .byte 1 /* Version number */
- .string "zR" /* NUL-terminated augmentation string */
- .uleb128 1 /* Code alignment factor */
- .sleb128 -4 /* Data alignment factor */
- .byte 8 /* Return address register column */
- .uleb128 1 /* Augmentation value length */
- .byte 0x1b /* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */
- .byte 0x0c /* DW_CFA_def_cfa */
- .uleb128 4
- .uleb128 4
- .byte 0x88 /* DW_CFA_offset, column 0x8 */
- .uleb128 1
- .align 4
- .LENDCIEDLSI:
- .long .LENDFDEDLSI-.LSTARTFDEDLSI /* Length FDE */
- .LSTARTFDEDLSI:
- .long .LSTARTFDEDLSI-.LSTARTFRAMEDLSI /* CIE pointer */
- .long .LSTART_vsyscall-. /* PC-relative start address */
- .long .LEND_vsyscall-.LSTART_vsyscall
- .uleb128 0
- /* What follows are the instructions for the table generation.
- We have to record all changes of the stack pointer. */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lpush_ecx-.LSTART_vsyscall
- .byte 0x0e /* DW_CFA_def_cfa_offset */
- .byte 0x08 /* RA at offset 8 now */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lpush_edx-.Lpush_ecx
- .byte 0x0e /* DW_CFA_def_cfa_offset */
- .byte 0x0c /* RA at offset 12 now */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lenter_kernel-.Lpush_edx
- .byte 0x0e /* DW_CFA_def_cfa_offset */
- .byte 0x10 /* RA at offset 16 now */
- .byte 0x85, 0x04 /* DW_CFA_offset %ebp -16 */
- /* Finally the epilogue. */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lpop_ebp-.Lenter_kernel
- .byte 0x0e /* DW_CFA_def_cfa_offset */
- .byte 0x0c /* RA at offset 12 now */
- .byte 0xc5 /* DW_CFA_restore %ebp */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lpop_edx-.Lpop_ebp
- .byte 0x0e /* DW_CFA_def_cfa_offset */
- .byte 0x08 /* RA at offset 8 now */
- .byte 0x04 /* DW_CFA_advance_loc4 */
- .long .Lpop_ecx-.Lpop_edx
- .byte 0x0e /* DW_CFA_def_cfa_offset */
- .byte 0x04 /* RA at offset 4 now */
- .align 4
- .LENDFDEDLSI:
- .previous
- /*
- * Get the common code for the sigreturn entry points.
- */
- #include "vsyscall-sigreturn.S"
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