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4ba92cd7 RH |
1 | /* |
2 | * safe-syscall.inc.S : host-specific assembly fragment | |
3 | * to handle signals occurring at the same time as system calls. | |
4 | * This is intended to be included by linux-user/safe-syscall.S | |
5 | * | |
6 | * Written by Richard Henderson <rth@twiddle.net> | |
7 | * Copyright (C) 2016 Red Hat, Inc. | |
8 | * | |
9 | * This work is licensed under the terms of the GNU GPL, version 2 or later. | |
10 | * See the COPYING file in the top-level directory. | |
11 | */ | |
12 | ||
b9d2af3c RH |
13 | .global safe_syscall_base |
14 | .global safe_syscall_start | |
15 | .global safe_syscall_end | |
16 | .type safe_syscall_base, @function | |
4ba92cd7 | 17 | |
b9d2af3c | 18 | .text |
4ba92cd7 | 19 | |
b9d2af3c RH |
20 | /* This is the entry point for making a system call. The calling |
21 | * convention here is that of a C varargs function with the | |
22 | * first argument an 'int *' to the signal_pending flag, the | |
23 | * second one the system call number (as a 'long'), and all further | |
24 | * arguments being syscall arguments (also 'long'). | |
b9d2af3c | 25 | */ |
4ba92cd7 RH |
26 | #if _CALL_ELF == 2 |
27 | safe_syscall_base: | |
b9d2af3c RH |
28 | .cfi_startproc |
29 | .localentry safe_syscall_base,0 | |
4ba92cd7 | 30 | #else |
b9d2af3c RH |
31 | .section ".opd","aw" |
32 | .align 3 | |
4ba92cd7 | 33 | safe_syscall_base: |
b9d2af3c RH |
34 | .quad .L.safe_syscall_base,.TOC.@tocbase,0 |
35 | .previous | |
4ba92cd7 | 36 | .L.safe_syscall_base: |
b9d2af3c | 37 | .cfi_startproc |
4ba92cd7 | 38 | #endif |
a3310c03 | 39 | /* We enter with r3 == &signal_pending |
b9d2af3c RH |
40 | * r4 == syscall number |
41 | * r5 ... r10 == syscall arguments | |
42 | * and return the result in r3 | |
43 | * and the syscall instruction needs | |
44 | * r0 == syscall number | |
45 | * r3 ... r8 == syscall arguments | |
46 | * and returns the result in r3 | |
47 | * Shuffle everything around appropriately. | |
48 | */ | |
49 | std 14, 16(1) /* Preserve r14 in SP+16 */ | |
50 | .cfi_offset 14, 16 | |
51 | mr 14, 3 /* signal_pending */ | |
52 | mr 0, 4 /* syscall number */ | |
53 | mr 3, 5 /* syscall arguments */ | |
54 | mr 4, 6 | |
55 | mr 5, 7 | |
56 | mr 6, 8 | |
57 | mr 7, 9 | |
58 | mr 8, 10 | |
4ba92cd7 | 59 | |
b9d2af3c RH |
60 | /* This next sequence of code works in conjunction with the |
61 | * rewind_if_safe_syscall_function(). If a signal is taken | |
62 | * and the interrupted PC is anywhere between 'safe_syscall_start' | |
63 | * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. | |
64 | * The code sequence must therefore be able to cope with this, and | |
65 | * the syscall instruction must be the final one in the sequence. | |
66 | */ | |
4ba92cd7 | 67 | safe_syscall_start: |
b9d2af3c RH |
68 | /* if signal_pending is non-zero, don't do the call */ |
69 | lwz 12, 0(14) | |
70 | cmpwi 0, 12, 0 | |
a3310c03 | 71 | bne- 2f |
b9d2af3c | 72 | sc |
4ba92cd7 | 73 | safe_syscall_end: |
b9d2af3c | 74 | /* code path when we did execute the syscall */ |
a3310c03 RH |
75 | ld 14, 16(1) /* restore r14 */ |
76 | bso- 1f | |
b9d2af3c | 77 | blr |
4ba92cd7 | 78 | |
b9d2af3c | 79 | /* code path when we didn't execute the syscall */ |
a3310c03 | 80 | 2: ld 14, 16(1) /* restore r14 */ |
af254a27 | 81 | addi 3, 0, QEMU_ERESTARTSYS |
a3310c03 RH |
82 | |
83 | /* code path setting errno */ | |
84 | 1: b safe_syscall_set_errno_tail | |
85 | nop /* per abi, for the linker to modify */ | |
86 | ||
b9d2af3c | 87 | .cfi_endproc |
4ba92cd7 RH |
88 | |
89 | #if _CALL_ELF == 2 | |
b9d2af3c | 90 | .size safe_syscall_base, .-safe_syscall_base |
4ba92cd7 | 91 | #else |
b9d2af3c RH |
92 | .size safe_syscall_base, .-.L.safe_syscall_base |
93 | .size .L.safe_syscall_base, .-.L.safe_syscall_base | |
4ba92cd7 | 94 | #endif |