| /* |
| * 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 |
| |
| /* 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'). |
| */ |
| safe_syscall_base: |
| .cfi_startproc |
| stmg %r6,%r15,48(%r15) /* save all call-saved registers */ |
| .cfi_offset %r15,-40 |
| .cfi_offset %r14,-48 |
| .cfi_offset %r13,-56 |
| .cfi_offset %r12,-64 |
| .cfi_offset %r11,-72 |
| .cfi_offset %r10,-80 |
| .cfi_offset %r9,-88 |
| .cfi_offset %r8,-96 |
| .cfi_offset %r7,-104 |
| .cfi_offset %r6,-112 |
| lgr %r1,%r15 |
| lg %r0,8(%r15) /* load eos */ |
| aghi %r15,-160 |
| .cfi_adjust_cfa_offset 160 |
| stg %r1,0(%r15) /* store back chain */ |
| stg %r0,8(%r15) /* store eos */ |
| |
| /* |
| * The syscall calling convention isn't the same as the C one: |
| * we enter with r2 == &signal_pending |
| * r3 == syscall number |
| * r4, r5, r6, (stack) == syscall arguments |
| * and return the result in r2 |
| * and the syscall instruction needs |
| * r1 == syscall number |
| * r2 ... r7 == syscall arguments |
| * and returns the result in r2 |
| * Shuffle everything around appropriately. |
| */ |
| lgr %r8,%r2 /* signal_pending pointer */ |
| lgr %r1,%r3 /* syscall number */ |
| lgr %r2,%r4 /* syscall args */ |
| lgr %r3,%r5 |
| lgr %r4,%r6 |
| lmg %r5,%r7,320(%r15) |
| |
| /* 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 */ |
| icm %r0,15,0(%r8) |
| jne 2f |
| svc 0 |
| safe_syscall_end: |
| |
| /* code path for having successfully executed the syscall */ |
| lg %r15,0(%r15) /* load back chain */ |
| .cfi_remember_state |
| .cfi_adjust_cfa_offset -160 |
| lmg %r6,%r15,48(%r15) /* load saved registers */ |
| |
| lghi %r0, -4095 /* check for syscall error */ |
| clgr %r2, %r0 |
| blr %r14 /* return on success */ |
| lcr %r2, %r2 /* create positive errno */ |
| jg safe_syscall_set_errno_tail |
| .cfi_restore_state |
| |
| /* code path when we didn't execute the syscall */ |
| 2: lg %r15,0(%r15) /* load back chain */ |
| .cfi_adjust_cfa_offset -160 |
| lmg %r6,%r15,48(%r15) /* load saved registers */ |
| lghi %r2, QEMU_ERESTARTSYS |
| jg safe_syscall_set_errno_tail |
| |
| .cfi_endproc |
| .size safe_syscall_base, .-safe_syscall_base |
