1*bbf15aafSRichard Henderson/* 2*bbf15aafSRichard Henderson * safe-syscall.inc.S : host-specific assembly fragment 3*bbf15aafSRichard Henderson * to handle signals occurring at the same time as system calls. 4*bbf15aafSRichard Henderson * This is intended to be included by common-user/safe-syscall.S 5*bbf15aafSRichard Henderson * 6*bbf15aafSRichard Henderson * Written by Richard Henderson <rth@twiddle.net> 7*bbf15aafSRichard Henderson * Copyright (C) 2016 Red Hat, Inc. 8*bbf15aafSRichard Henderson * 9*bbf15aafSRichard Henderson * This work is licensed under the terms of the GNU GPL, version 2 or later. 10*bbf15aafSRichard Henderson * See the COPYING file in the top-level directory. 11*bbf15aafSRichard Henderson */ 12*bbf15aafSRichard Henderson 13*bbf15aafSRichard Henderson .global safe_syscall_base 14*bbf15aafSRichard Henderson .global safe_syscall_start 15*bbf15aafSRichard Henderson .global safe_syscall_end 16*bbf15aafSRichard Henderson .type safe_syscall_base, @function 17*bbf15aafSRichard Henderson 18*bbf15aafSRichard Henderson .text 19*bbf15aafSRichard Henderson 20*bbf15aafSRichard Henderson /* This is the entry point for making a system call. The calling 21*bbf15aafSRichard Henderson * convention here is that of a C varargs function with the 22*bbf15aafSRichard Henderson * first argument an 'int *' to the signal_pending flag, the 23*bbf15aafSRichard Henderson * second one the system call number (as a 'long'), and all further 24*bbf15aafSRichard Henderson * arguments being syscall arguments (also 'long'). 25*bbf15aafSRichard Henderson */ 26*bbf15aafSRichard Henderson#if _CALL_ELF == 2 27*bbf15aafSRichard Hendersonsafe_syscall_base: 28*bbf15aafSRichard Henderson .cfi_startproc 29*bbf15aafSRichard Henderson .localentry safe_syscall_base,0 30*bbf15aafSRichard Henderson#else 31*bbf15aafSRichard Henderson .section ".opd","aw" 32*bbf15aafSRichard Henderson .align 3 33*bbf15aafSRichard Hendersonsafe_syscall_base: 34*bbf15aafSRichard Henderson .quad .L.safe_syscall_base,.TOC.@tocbase,0 35*bbf15aafSRichard Henderson .previous 36*bbf15aafSRichard Henderson.L.safe_syscall_base: 37*bbf15aafSRichard Henderson .cfi_startproc 38*bbf15aafSRichard Henderson#endif 39*bbf15aafSRichard Henderson /* We enter with r3 == &signal_pending 40*bbf15aafSRichard Henderson * r4 == syscall number 41*bbf15aafSRichard Henderson * r5 ... r10 == syscall arguments 42*bbf15aafSRichard Henderson * and return the result in r3 43*bbf15aafSRichard Henderson * and the syscall instruction needs 44*bbf15aafSRichard Henderson * r0 == syscall number 45*bbf15aafSRichard Henderson * r3 ... r8 == syscall arguments 46*bbf15aafSRichard Henderson * and returns the result in r3 47*bbf15aafSRichard Henderson * Shuffle everything around appropriately. 48*bbf15aafSRichard Henderson */ 49*bbf15aafSRichard Henderson std 14, 16(1) /* Preserve r14 in SP+16 */ 50*bbf15aafSRichard Henderson .cfi_offset 14, 16 51*bbf15aafSRichard Henderson mr 14, 3 /* signal_pending */ 52*bbf15aafSRichard Henderson mr 0, 4 /* syscall number */ 53*bbf15aafSRichard Henderson mr 3, 5 /* syscall arguments */ 54*bbf15aafSRichard Henderson mr 4, 6 55*bbf15aafSRichard Henderson mr 5, 7 56*bbf15aafSRichard Henderson mr 6, 8 57*bbf15aafSRichard Henderson mr 7, 9 58*bbf15aafSRichard Henderson mr 8, 10 59*bbf15aafSRichard Henderson 60*bbf15aafSRichard Henderson /* This next sequence of code works in conjunction with the 61*bbf15aafSRichard Henderson * rewind_if_safe_syscall_function(). If a signal is taken 62*bbf15aafSRichard Henderson * and the interrupted PC is anywhere between 'safe_syscall_start' 63*bbf15aafSRichard Henderson * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. 64*bbf15aafSRichard Henderson * The code sequence must therefore be able to cope with this, and 65*bbf15aafSRichard Henderson * the syscall instruction must be the final one in the sequence. 66*bbf15aafSRichard Henderson */ 67*bbf15aafSRichard Hendersonsafe_syscall_start: 68*bbf15aafSRichard Henderson /* if signal_pending is non-zero, don't do the call */ 69*bbf15aafSRichard Henderson lwz 12, 0(14) 70*bbf15aafSRichard Henderson cmpwi 0, 12, 0 71*bbf15aafSRichard Henderson bne- 2f 72*bbf15aafSRichard Henderson sc 73*bbf15aafSRichard Hendersonsafe_syscall_end: 74*bbf15aafSRichard Henderson /* code path when we did execute the syscall */ 75*bbf15aafSRichard Henderson ld 14, 16(1) /* restore r14 */ 76*bbf15aafSRichard Henderson bso- 1f 77*bbf15aafSRichard Henderson blr 78*bbf15aafSRichard Henderson 79*bbf15aafSRichard Henderson /* code path when we didn't execute the syscall */ 80*bbf15aafSRichard Henderson2: ld 14, 16(1) /* restore r14 */ 81*bbf15aafSRichard Henderson addi 3, 0, QEMU_ERESTARTSYS 82*bbf15aafSRichard Henderson 83*bbf15aafSRichard Henderson /* code path setting errno */ 84*bbf15aafSRichard Henderson1: b safe_syscall_set_errno_tail 85*bbf15aafSRichard Henderson nop /* per abi, for the linker to modify */ 86*bbf15aafSRichard Henderson 87*bbf15aafSRichard Henderson .cfi_endproc 88*bbf15aafSRichard Henderson 89*bbf15aafSRichard Henderson#if _CALL_ELF == 2 90*bbf15aafSRichard Henderson .size safe_syscall_base, .-safe_syscall_base 91*bbf15aafSRichard Henderson#else 92*bbf15aafSRichard Henderson .size safe_syscall_base, .-.L.safe_syscall_base 93*bbf15aafSRichard Henderson .size .L.safe_syscall_base, .-.L.safe_syscall_base 94*bbf15aafSRichard Henderson#endif 95