linux-user: Create special-errno.h

Pull the two internal errno used by qemu internally into their own
header file.  This includes the one define required by safe-syscall.S.

Reviewed-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/cpu_loop-common.h

@@ -21,6 +21,7 @@
 #define CPU_LOOP_COMMON_H
 
 #include "exec/log.h"
+#include "special-errno.h"
 
 #define EXCP_DUMP(env, fmt, ...)                                        \
 do {                                                                    \

linux-user/generic/target_errno_defs.h

@@ -147,21 +147,4 @@
 #define TARGET_ERFKILL         132     /* Operation not possible due to RF-kill */
 #define TARGET_EHWPOISON       133     /* Memory page has hardware error */
 
-/* QEMU internal, not visible to the guest. This is returned when a
- * system call should be restarted, to tell the main loop that it
- * should wind the guest PC backwards so it will re-execute the syscall
- * after handling any pending signals. They match with the ones the guest
- * kernel uses for the same purpose.
- */
-#define QEMU_ERESTARTSYS     512     /* Restart system call (if SA_RESTART) */
-
-/* QEMU internal, not visible to the guest. This is returned by the
- * do_sigreturn() code after a successful sigreturn syscall, to indicate
- * that it has correctly set the guest registers and so the main loop
- * should not touch them. We use the value the guest would use for
- * ERESTART_NOINTR (which is kernel internal) to guarantee that we won't
- * clash with a valid guest errno now or in the future.
- */
-#define QEMU_ESIGRETURN 513     /* Return from signal */
-
 #endif

linux-user/safe-syscall.S

@@ -10,7 +10,7 @@
  * See the COPYING file in the top-level directory.
  */
 
-#include "target_errno_defs.h"
+#include "special-errno.h"
 
 /* We have the correct host directory on our include path
  * so that this will pull in the right fragment for the architecture.

linux-user/signal-common.h

@@ -20,6 +20,8 @@
 #ifndef SIGNAL_COMMON_H
 #define SIGNAL_COMMON_H
 
+#include "special-errno.h"
+
 /* Fallback addresses into sigtramp page. */
 extern abi_ulong default_sigreturn;
 extern abi_ulong default_rt_sigreturn;

linux-user/special-errno.h

@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * QEMU internal errno values for implementing user-only POSIX.
+ *
+ *  Copyright (c) 2003 Fabrice Bellard
+ *  Copyright (c) 2021 Linaro, Ltd.
+ */
+
+#ifndef SPECIAL_ERRNO_H
+#define SPECIAL_ERRNO_H
+
+/*
+ * All of these are QEMU internal, not visible to the guest.
+ * They should be chosen so as to not overlap with any host
+ * or guest errno.
+ */
+
+/*
+ * This is returned when a system call should be restarted, to tell the
+ * main loop that it should wind the guest PC backwards so it will
+ * re-execute the syscall after handling any pending signals.
+ */
+#define QEMU_ERESTARTSYS  512
+
+/*
+ * This is returned after a successful sigreturn syscall, to indicate
+ * that it has correctly set the guest registers and so the main loop
+ * should not touch them.
+ */
+#define QEMU_ESIGRETURN   513
+
+#endif /* SPECIAL_ERRNO_H */

linux-user/syscall.c

@@ -136,6 +136,7 @@
 #include "qemu/guest-random.h"
 #include "qemu/selfmap.h"
 #include "user/syscall-trace.h"
+#include "special-errno.h"
 #include "qapi/error.h"
 #include "fd-trans.h"
 #include "tcg/tcg.h"