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 /* This is the entry point for making a system call. The calling 19*bbf15aafSRichard Henderson * convention here is that of a C varargs function with the 20*bbf15aafSRichard Henderson * first argument an 'int *' to the signal_pending flag, the 21*bbf15aafSRichard Henderson * second one the system call number (as a 'long'), and all further 22*bbf15aafSRichard Henderson * arguments being syscall arguments (also 'long'). 23*bbf15aafSRichard Henderson */ 24*bbf15aafSRichard Hendersonsafe_syscall_base: 25*bbf15aafSRichard Henderson .cfi_startproc 26*bbf15aafSRichard Henderson stmg %r6,%r15,48(%r15) /* save all call-saved registers */ 27*bbf15aafSRichard Henderson .cfi_offset %r15,-40 28*bbf15aafSRichard Henderson .cfi_offset %r14,-48 29*bbf15aafSRichard Henderson .cfi_offset %r13,-56 30*bbf15aafSRichard Henderson .cfi_offset %r12,-64 31*bbf15aafSRichard Henderson .cfi_offset %r11,-72 32*bbf15aafSRichard Henderson .cfi_offset %r10,-80 33*bbf15aafSRichard Henderson .cfi_offset %r9,-88 34*bbf15aafSRichard Henderson .cfi_offset %r8,-96 35*bbf15aafSRichard Henderson .cfi_offset %r7,-104 36*bbf15aafSRichard Henderson .cfi_offset %r6,-112 37*bbf15aafSRichard Henderson lgr %r1,%r15 38*bbf15aafSRichard Henderson lg %r0,8(%r15) /* load eos */ 39*bbf15aafSRichard Henderson aghi %r15,-160 40*bbf15aafSRichard Henderson .cfi_adjust_cfa_offset 160 41*bbf15aafSRichard Henderson stg %r1,0(%r15) /* store back chain */ 42*bbf15aafSRichard Henderson stg %r0,8(%r15) /* store eos */ 43*bbf15aafSRichard Henderson 44*bbf15aafSRichard Henderson /* 45*bbf15aafSRichard Henderson * The syscall calling convention isn't the same as the C one: 46*bbf15aafSRichard Henderson * we enter with r2 == &signal_pending 47*bbf15aafSRichard Henderson * r3 == syscall number 48*bbf15aafSRichard Henderson * r4, r5, r6, (stack) == syscall arguments 49*bbf15aafSRichard Henderson * and return the result in r2 50*bbf15aafSRichard Henderson * and the syscall instruction needs 51*bbf15aafSRichard Henderson * r1 == syscall number 52*bbf15aafSRichard Henderson * r2 ... r7 == syscall arguments 53*bbf15aafSRichard Henderson * and returns the result in r2 54*bbf15aafSRichard Henderson * Shuffle everything around appropriately. 55*bbf15aafSRichard Henderson */ 56*bbf15aafSRichard Henderson lgr %r8,%r2 /* signal_pending pointer */ 57*bbf15aafSRichard Henderson lgr %r1,%r3 /* syscall number */ 58*bbf15aafSRichard Henderson lgr %r2,%r4 /* syscall args */ 59*bbf15aafSRichard Henderson lgr %r3,%r5 60*bbf15aafSRichard Henderson lgr %r4,%r6 61*bbf15aafSRichard Henderson lmg %r5,%r7,320(%r15) 62*bbf15aafSRichard Henderson 63*bbf15aafSRichard Henderson /* This next sequence of code works in conjunction with the 64*bbf15aafSRichard Henderson * rewind_if_safe_syscall_function(). If a signal is taken 65*bbf15aafSRichard Henderson * and the interrupted PC is anywhere between 'safe_syscall_start' 66*bbf15aafSRichard Henderson * and 'safe_syscall_end' then we rewind it to 'safe_syscall_start'. 67*bbf15aafSRichard Henderson * The code sequence must therefore be able to cope with this, and 68*bbf15aafSRichard Henderson * the syscall instruction must be the final one in the sequence. 69*bbf15aafSRichard Henderson */ 70*bbf15aafSRichard Hendersonsafe_syscall_start: 71*bbf15aafSRichard Henderson /* if signal_pending is non-zero, don't do the call */ 72*bbf15aafSRichard Henderson icm %r0,15,0(%r8) 73*bbf15aafSRichard Henderson jne 2f 74*bbf15aafSRichard Henderson svc 0 75*bbf15aafSRichard Hendersonsafe_syscall_end: 76*bbf15aafSRichard Henderson 77*bbf15aafSRichard Henderson /* code path for having successfully executed the syscall */ 78*bbf15aafSRichard Henderson lg %r15,0(%r15) /* load back chain */ 79*bbf15aafSRichard Henderson .cfi_remember_state 80*bbf15aafSRichard Henderson .cfi_adjust_cfa_offset -160 81*bbf15aafSRichard Henderson lmg %r6,%r15,48(%r15) /* load saved registers */ 82*bbf15aafSRichard Henderson 83*bbf15aafSRichard Henderson lghi %r0, -4095 /* check for syscall error */ 84*bbf15aafSRichard Henderson clgr %r2, %r0 85*bbf15aafSRichard Henderson blr %r14 /* return on success */ 86*bbf15aafSRichard Henderson lcr %r2, %r2 /* create positive errno */ 87*bbf15aafSRichard Henderson jg safe_syscall_set_errno_tail 88*bbf15aafSRichard Henderson .cfi_restore_state 89*bbf15aafSRichard Henderson 90*bbf15aafSRichard Henderson /* code path when we didn't execute the syscall */ 91*bbf15aafSRichard Henderson2: lg %r15,0(%r15) /* load back chain */ 92*bbf15aafSRichard Henderson .cfi_adjust_cfa_offset -160 93*bbf15aafSRichard Henderson lmg %r6,%r15,48(%r15) /* load saved registers */ 94*bbf15aafSRichard Henderson lghi %r2, QEMU_ERESTARTSYS 95*bbf15aafSRichard Henderson jg safe_syscall_set_errno_tail 96*bbf15aafSRichard Henderson 97*bbf15aafSRichard Henderson .cfi_endproc 98*bbf15aafSRichard Henderson .size safe_syscall_base, .-safe_syscall_base 99