@@ -12,4 +12,7 @@
#ifndef MIPS_HOSTDEP_H
#define MIPS_HOSTDEP_H
+/* We have a safe-syscall.inc.S */
+#define HAVE_SAFE_SYSCALL
+
#endif
new file mode 100644
@@ -0,0 +1,123 @@
+/*
+ * 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
+ *
+ * Written by Richard Henderson <richard.henderson@linaro.org>
+ * Copyright (C) 2021 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.
+ */
+
+#include "sys/regdef.h"
+#include "sys/asm.h"
+
+ .text
+ .set nomips16
+ .set reorder
+
+ .global safe_syscall_start
+ .global safe_syscall_end
+ .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').
+ */
+
+LEAF(safe_syscall_base)
+ .cfi_startproc
+#if _MIPS_SIM == _ABIO32
+ /*
+ * The syscall calling convention is nearly the same as C:
+ * we enter with a0 == &signal_pending
+ * a1 == syscall number
+ * a2, a3, stack == syscall arguments
+ * and return the result in a0
+ * and the syscall instruction needs
+ * v0 == syscall number
+ * a0 ... a3, stack == syscall arguments
+ * and returns the result in v0
+ * Shuffle everything around appropriately.
+ */
+ move t0, a0 /* signal_pending pointer */
+ move v0, a1 /* syscall number */
+ move a0, a2 /* syscall arguments */
+ move a1, a3
+ lw a2, 16(sp)
+ lw a3, 20(sp)
+ lw t4, 24(sp)
+ lw t5, 28(sp)
+ lw t6, 32(sp)
+ lw t7, 40(sp)
+ sw t4, 16(sp)
+ sw t5, 20(sp)
+ sw t6, 24(sp)
+ sw t7, 28(sp)
+#else
+ /*
+ * 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
+ * v0 == syscall number
+ * a0 ... a5 == syscall arguments
+ * and returns the result in v0
+ * Shuffle everything around appropriately.
+ */
+ move t0, a0 /* signal_pending pointer */
+ move v0, a1 /* syscall number */
+ move a0, a2 /* syscall arguments */
+ move a1, a3
+ move a2, a4
+ move a3, a5
+ move a4, a6
+ move a5, a7
+#endif
+
+ /*
+ * 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 */
+ lw t1, 0(t0)
+ bnez t1, 2f
+ syscall
+safe_syscall_end:
+
+ /* code path for having successfully executed the syscall */
+ bnez a3, 1f
+ jr ra
+
+ /* code path when we didn't execute the syscall */
+2: li v0, TARGET_ERESTARTSYS
+
+ /* code path setting errno */
+ /*
+ * We didn't setup GP on entry, optimistic of the syscall success.
+ * We must do so now to load the address of the helper, as required
+ * by the ABI, into t9.
+ *
+ * Note that SETUP_GPX and SETUP_GPX64 are themselves conditional,
+ * so we can simply let the one that's not empty succeed.
+ */
+1: USE_ALT_CP(t0)
+ SETUP_GPX(t1)
+ SETUP_GPX64(t0, t1)
+ PTR_LA t9, safe_syscall_set_errno_tail
+ jr t9
+
+ .cfi_endproc
+END(safe_syscall_base)
Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- linux-user/host/mips/hostdep.h | 3 + linux-user/host/mips/safe-syscall.inc.S | 123 ++++++++++++++++++++++++ 2 files changed, 126 insertions(+) create mode 100644 linux-user/host/mips/safe-syscall.inc.S