| /* |
| * safe-syscall.inc.S : host-specific assembly fragment |
| * to handle signals occurring at the same time as system calls. |
| * This is intended to be included by common-user/safe-syscall.S |
| * |
| * Written by Richard Henderson <rth@twiddle.net> |
| * Copyright (C) 2016 Red Hat, Inc. |
| * |
| * This work is licensed under the terms of the GNU GPL, version 2 or later. |
| * See the COPYING file in the top-level directory. |
| */ |
| |
| .global safe_syscall_base |
| .global safe_syscall_start |
| .global safe_syscall_end |
| .type safe_syscall_base, @function |
| |
| .text |
| |
| /* This is the entry point for making a system call. The calling |
| * convention here is that of a C varargs function with the |
| * first argument an 'int *' to the signal_pending flag, the |
| * second one the system call number (as a 'long'), and all further |
| * arguments being syscall arguments (also 'long'). |
| */ |
| #if _CALL_ELF == 2 |
| safe_syscall_base: |
| .cfi_startproc |
| .localentry safe_syscall_base,0 |
| #else |
| .section ".opd","aw" |
| .align 3 |
| safe_syscall_base: |
| .quad .L.safe_syscall_base,.TOC.@tocbase,0 |
| .previous |
| .L.safe_syscall_base: |
| .cfi_startproc |
| #endif |
| /* We enter with r3 == &signal_pending |
| * r4 == syscall number |
| * r5 ... r10 == syscall arguments |
| * and return the result in r3 |
| * and the syscall instruction needs |
| * r0 == syscall number |
| * r3 ... r8 == syscall arguments |
| * and returns the result in r3 |
| * Shuffle everything around appropriately. |
| */ |
| std 14, 16(1) /* Preserve r14 in SP+16 */ |
| .cfi_offset 14, 16 |
| mr 14, 3 /* signal_pending */ |
| mr 0, 4 /* syscall number */ |
| mr 3, 5 /* syscall arguments */ |
| mr 4, 6 |
| mr 5, 7 |
| mr 6, 8 |
| mr 7, 9 |
| mr 8, 10 |
| |
| /* This next sequence of code works in conjunction with the |
| * rewind_if_safe_syscall_function(). If a signal is taken |
| * and the interrupted PC is anywhere between 'safe_syscall_start' |
| * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. |
| * The code sequence must therefore be able to cope with this, and |
| * the syscall instruction must be the final one in the sequence. |
| */ |
| safe_syscall_start: |
| /* if signal_pending is non-zero, don't do the call */ |
| lwz 12, 0(14) |
| cmpwi 0, 12, 0 |
| bne- 2f |
| sc |
| safe_syscall_end: |
| /* code path when we did execute the syscall */ |
| ld 14, 16(1) /* restore r14 */ |
| bso- 1f |
| blr |
| |
| /* code path when we didn't execute the syscall */ |
| 2: ld 14, 16(1) /* restore r14 */ |
| addi 3, 0, QEMU_ERESTARTSYS |
| |
| /* code path setting errno */ |
| 1: b safe_syscall_set_errno_tail |
| nop /* per abi, for the linker to modify */ |
| |
| .cfi_endproc |
| |
| #if _CALL_ELF == 2 |
| .size safe_syscall_base, .-safe_syscall_base |
| #else |
| .size safe_syscall_base, .-.L.safe_syscall_base |
| .size .L.safe_syscall_base, .-.L.safe_syscall_base |
| #endif |
