@@ -8,4 +8,27 @@
#ifndef LOONGARCH64_HOSTDEP_H
#define LOONGARCH64_HOSTDEP_H
+/* We have a safe-syscall.inc.S */
+#define HAVE_SAFE_SYSCALL
+
+#ifndef __ASSEMBLER__
+
+/* These are defined by the safe-syscall.inc.S file */
+extern char safe_syscall_start[];
+extern char safe_syscall_end[];
+
+/* Adjust the signal context to rewind out of safe-syscall if we're in it */
+static inline void rewind_if_in_safe_syscall(void *puc)
+{
+ ucontext_t *uc = puc;
+ unsigned long long *pcreg = &uc->uc_mcontext.__pc;
+
+ if (*pcreg > (uintptr_t)safe_syscall_start
+ && *pcreg < (uintptr_t)safe_syscall_end) {
+ *pcreg = (uintptr_t)safe_syscall_start;
+ }
+}
+
+#endif /* __ASSEMBLER__ */
+
#endif
new file mode 100644
@@ -0,0 +1,80 @@
+/*
+ * 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 linux-user/safe-syscall.S
+ *
+ * Ported to LoongArch by WANG Xuerui <git@xen0n.name>
+ *
+ * Based on safe-syscall.inc.S code for every other architecture,
+ * 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').
+ * We return a long which is the syscall's return value, which
+ * may be negative-errno on failure. Conversion to the
+ * -1-and-errno-set convention is done by the calling wrapper.
+ */
+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
+
+ /*
+ * 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, $t0, 0
+ bnez $t1, 0f
+ syscall 0
+safe_syscall_end:
+ /* code path for having successfully executed the syscall */
+ jr $ra
+
+0:
+ /* code path when we didn't execute the syscall */
+ li.w $a0, -TARGET_ERESTARTSYS
+ jr $ra
+ .cfi_endproc
+
+ .size safe_syscall_base, .-safe_syscall_base