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