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[PULL 28/31] common-user: Add safe syscall handling for loongarch64 host
From: |
Richard Henderson |
Subject: |
[PULL 28/31] common-user: Add safe syscall handling for loongarch64 hosts |
Date: |
Tue, 21 Dec 2021 08:47:34 -0800 |
From: WANG Xuerui <git@xen0n.name>
Signed-off-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211221054105.178795-29-git@xen0n.name>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
.../host/loongarch64/safe-syscall.inc.S | 90 +++++++++++++++++++
1 file changed, 90 insertions(+)
create mode 100644 common-user/host/loongarch64/safe-syscall.inc.S
diff --git a/common-user/host/loongarch64/safe-syscall.inc.S
b/common-user/host/loongarch64/safe-syscall.inc.S
new file mode 100644
index 0000000000..b88a069c45
--- /dev/null
+++ b/common-user/host/loongarch64/safe-syscall.inc.S
@@ -0,0 +1,90 @@
+/*
+ * 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
+ *
+ * Ported to LoongArch by WANG Xuerui <git@xen0n.name>
+ *
+ * Based on safe-syscall.inc.S code for RISC-V,
+ * originally written by Richard Henderson <rth@twiddle.net>
+ * Copyright (C) 2018 Linaro, 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
+ .type safe_syscall_start, @function
+ .type safe_syscall_end, @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
+ /*
+ * The syscall calling convention is nearly the same as C:
+ * we enter with a0 == &signal_pending
+ * a1 == syscall number
+ * a2 ... a7 == syscall arguments
+ * and return the result in a0
+ * and the syscall instruction needs
+ * a7 == syscall number
+ * a0 ... a5 == syscall arguments
+ * and returns the result in a0
+ * Shuffle everything around appropriately.
+ */
+ move $t0, $a0 /* signal_pending pointer */
+ move $t1, $a1 /* syscall number */
+ move $a0, $a2 /* syscall arguments */
+ move $a1, $a3
+ move $a2, $a4
+ move $a3, $a5
+ move $a4, $a6
+ move $a5, $a7
+ move $a7, $t1
+
+ /*
+ * We need to preserve the signal_pending pointer but t0 is
+ * clobbered by syscalls on LoongArch, so we need to move it
+ * somewhere else, ideally both preserved across syscalls and
+ * clobbered by procedure calls so we don't have to allocate a
+ * stack frame; a6 is just the register we want here.
+ */
+ move $a6, $t0
+
+ /*
+ * 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 */
+ ld.w $t1, $a6, 0
+ bnez $t1, 2f
+ syscall 0
+safe_syscall_end:
+ /* code path for having successfully executed the syscall */
+ li.w $t2, -4096
+ bgtu $a0, $t2, 0f
+ jr $ra
+
+ /* code path setting errno */
+0: sub.d $a0, $zero, $a0
+ b safe_syscall_set_errno_tail
+
+ /* code path when we didn't execute the syscall */
+2: li.w $a0, QEMU_ERESTARTSYS
+ b safe_syscall_set_errno_tail
+ .cfi_endproc
+ .size safe_syscall_base, .-safe_syscall_base
--
2.25.1
- [PULL 19/31] tcg/loongarch64: Implement br/brcond ops, (continued)
- [PULL 19/31] tcg/loongarch64: Implement br/brcond ops, Richard Henderson, 2021/12/21
- [PULL 11/31] tcg/loongarch64: Implement sign-/zero-extension ops, Richard Henderson, 2021/12/21
- [PULL 23/31] tcg/loongarch64: Add softmmu load/store helpers, implement qemu_ld/qemu_st ops, Richard Henderson, 2021/12/21
- [PULL 20/31] tcg/loongarch64: Implement setcond ops, Richard Henderson, 2021/12/21
- [PULL 26/31] tcg/loongarch64: Implement tcg_target_init, Richard Henderson, 2021/12/21
- [PULL 08/31] tcg/loongarch64: Implement the memory barrier op, Richard Henderson, 2021/12/21
- [PULL 22/31] tcg/loongarch64: Implement simple load/store ops, Richard Henderson, 2021/12/21
- [PULL 10/31] tcg/loongarch64: Implement goto_ptr, Richard Henderson, 2021/12/21
- [PULL 24/31] tcg/loongarch64: Implement tcg_target_qemu_prologue, Richard Henderson, 2021/12/21
- [PULL 29/31] linux-user: Implement CPU-specific signal handler for loongarch64 hosts, Richard Henderson, 2021/12/21
- [PULL 28/31] common-user: Add safe syscall handling for loongarch64 hosts,
Richard Henderson <=
- [PULL 30/31] configure, meson.build: Mark support for loongarch64 hosts, Richard Henderson, 2021/12/21
- [PULL 31/31] tests/docker: Add gentoo-loongarch64-cross image and run cross builds in GitLab, Richard Henderson, 2021/12/21
- [PULL 21/31] tcg/loongarch64: Implement tcg_out_call, Richard Henderson, 2021/12/21
- [PULL 27/31] tcg/loongarch64: Register the JIT, Richard Henderson, 2021/12/21
- [PULL 25/31] tcg/loongarch64: Implement exit_tb/goto_tb, Richard Henderson, 2021/12/21