linux-user: Renumber TARGET_QEMU_ESIGRETURN, make it not arch-specific

Currently we define a QEMU-internal errno TARGET_QEMU_ESIGRETURN
only on the MIPS and PPC targets; move this to errno_defs.h
so it is available for all architectures, and renumber it to 513.
We pick 513 because this is safe from future use as a system call return
value: Linux uses it as ERESTART_NOINTR internally and never allows that
errno to escape to userspace.

Signed-off-by: Timothy Edward Baldwin <T.E.Baldwin99@members.leeds.ac.uk>
Message-id: 1441497448-32489-4-git-send-email-T.E.Baldwin99@members.leeds.ac.uk
[PMM: TARGET_ERESTARTSYS split out into preceding patch, add comment]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/linux-user/errno_defs.h b/linux-user/errno_defs.h
index b7a8c9f..65522c4 100644
--- a/linux-user/errno_defs.h
+++ b/linux-user/errno_defs.h
@@ -147,3 +147,12 @@
  * kernel uses for the same purpose.
  */
 #define TARGET_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 TARGET_QEMU_ESIGRETURN 513     /* Return from signal */