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/*
11 * The caller puts arg2 in %ecx, which gets pushed. The kernel will use
12 * %ecx itself for arg2. The pushing is because the sysexit instruction
13 * (found in entry.S) requires that we clobber %ecx with the desired %esp.
14 * User code might expect that %ecx is unclobbered though, as it would be
15 * for returning via the iret instruction, so we must push and pop.
16 *
17 * The caller puts arg3 in %edx, which the sysexit instruction requires
18 * for %eip. Thus, exactly as for arg2, we must push and pop.
19 *
20 * Arg6 is different. The caller puts arg6 in %ebp. Since the sysenter
21 * instruction clobbers %esp, the user's %esp won't even survive entry
22 * into the kernel. We store %esp in %ebp. Code in entry.S must fetch
23 * arg6 from the stack.
24 *
25 * You can not use this vsyscall for the clone() syscall because the
26 * three dwords on the parent stack do not get copied to the child.
27 */
28	.text
29	.globl __kernel_vsyscall
30	.type __kernel_vsyscall,@function
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	jmp .Lenter_kernel
47	/* 16: System call normal return point is here! */
48	.globl SYSENTER_RETURN	/* Symbol used by sysenter.c  */
49SYSENTER_RETURN:
50	pop %ebp
51.Lpop_ebp:
52	pop %edx
53.Lpop_edx:
54	pop %ecx
55.Lpop_ecx:
56	ret
57.LEND_vsyscall:
58	.size __kernel_vsyscall,.-.LSTART_vsyscall
59	.previous
60
61	.section .eh_frame,"a",@progbits
62.LSTARTFRAMEDLSI:
63	.long .LENDCIEDLSI-.LSTARTCIEDLSI
64.LSTARTCIEDLSI:
65	.long 0			/* CIE ID */
66	.byte 1			/* Version number */
67	.string "zR"		/* NUL-terminated augmentation string */
68	.uleb128 1		/* Code alignment factor */
69	.sleb128 -4		/* Data alignment factor */
70	.byte 8			/* Return address register column */
71	.uleb128 1		/* Augmentation value length */
72	.byte 0x1b		/* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */
73	.byte 0x0c		/* DW_CFA_def_cfa */
74	.uleb128 4
75	.uleb128 4
76	.byte 0x88		/* DW_CFA_offset, column 0x8 */
77	.uleb128 1
78	.align 4
79.LENDCIEDLSI:
80	.long .LENDFDEDLSI-.LSTARTFDEDLSI /* Length FDE */
81.LSTARTFDEDLSI:
82	.long .LSTARTFDEDLSI-.LSTARTFRAMEDLSI /* CIE pointer */
83	.long .LSTART_vsyscall-.	/* PC-relative start address */
84	.long .LEND_vsyscall-.LSTART_vsyscall
85	.uleb128 0
86	/* What follows are the instructions for the table generation.
87	   We have to record all changes of the stack pointer.  */
88	.byte 0x04		/* DW_CFA_advance_loc4 */
89	.long .Lpush_ecx-.LSTART_vsyscall
90	.byte 0x0e		/* DW_CFA_def_cfa_offset */
91	.byte 0x08		/* RA at offset 8 now */
92	.byte 0x04		/* DW_CFA_advance_loc4 */
93	.long .Lpush_edx-.Lpush_ecx
94	.byte 0x0e		/* DW_CFA_def_cfa_offset */
95	.byte 0x0c		/* RA at offset 12 now */
96	.byte 0x04		/* DW_CFA_advance_loc4 */
97	.long .Lenter_kernel-.Lpush_edx
98	.byte 0x0e		/* DW_CFA_def_cfa_offset */
99	.byte 0x10		/* RA at offset 16 now */
100	.byte 0x85, 0x04	/* DW_CFA_offset %ebp -16 */
101	/* Finally the epilogue.  */
102	.byte 0x04		/* DW_CFA_advance_loc4 */
103	.long .Lpop_ebp-.Lenter_kernel
104	.byte 0x0e		/* DW_CFA_def_cfa_offset */
105	.byte 0x0c		/* RA at offset 12 now */
106	.byte 0xc5		/* DW_CFA_restore %ebp */
107	.byte 0x04		/* DW_CFA_advance_loc4 */
108	.long .Lpop_edx-.Lpop_ebp
109	.byte 0x0e		/* DW_CFA_def_cfa_offset */
110	.byte 0x08		/* RA at offset 8 now */
111	.byte 0x04		/* DW_CFA_advance_loc4 */
112	.long .Lpop_ecx-.Lpop_edx
113	.byte 0x0e		/* DW_CFA_def_cfa_offset */
114	.byte 0x04		/* RA at offset 4 now */
115	.align 4
116.LENDFDEDLSI:
117	.previous
118
119/*
120 * Get the common code for the sigreturn entry points.
121 */
122#include "vsyscall-sigreturn.S"
123