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LeafOS / LeafOS-Devices / android_kernel_samsung_exynos9820 / 0a1340c185734a57fbf4775927966ad4a1347b02 / . / arch / i386 / kernel / vsyscall-sysenter.S
blob: 1a36d26e15eb0c6d370832ee166dd0fba3700f59 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700[diff] [blame]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
Albert D. Cahalan581141c2006-02-14 13:53:20 -0800[diff] [blame]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.
Chuck Ebbertbe0a3912006-03-23 02:59:48 -0800[diff] [blame]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.
Albert D. Cahalan581141c2006-02-14 13:53:20 -0800[diff] [blame]27 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700[diff] [blame]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
Ingo Molnare6e54942006-06-27 02:53:50 -0700[diff] [blame]45 /* 14: System call restart point is here! (SYSENTER_RETURN-2) */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700[diff] [blame]46 jmp .Lenter_kernel
47 /* 16: System call normal return point is here! */
Ingo Molnare6e54942006-06-27 02:53:50 -0700[diff] [blame]48 .globl SYSENTER_RETURN /* Symbol used by sysenter.c */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700[diff] [blame]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"