microblaze: fix the horror with restarts of sigreturn()
solution a-la arm one - pick a callee-saved register (r30), set it
non-zero when entering a syscall, have sigreturn wrapper zero it out
and pass the value in it to do_notify_resume() as "in_syscall" (actually,
"restarts allowed") argument.
Note that we don't give a damn about ret_from_fork() - return value
is not restart-worthy anyway.
Possible remaining bug: on !MMU we still have _debug_exception()
restartable. If it hits with -ERESTART_... accidentally in r3, fun happens.
MMU does _not_ have _debug_exception() restartable. If that's decided to
be a bug (as I strongly suspect it to be), we'll just need to replace
setting r30 to 1 with setting r30 to 0 in !MMU _debug_exception().
Up to microblaze maintainers...
[folded a fix from Michal]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/microblaze/kernel/entry.S b/arch/microblaze/kernel/entry.S
index c217367..18908d2 100644
--- a/arch/microblaze/kernel/entry.S
+++ b/arch/microblaze/kernel/entry.S
@@ -353,6 +353,7 @@
/* Figure out which function to use for this system call. */
/* Note Microblaze barrel shift is optional, so don't rely on it */
add r12, r12, r12; /* convert num -> ptr */
+ addi r30, r0, 1 /* restarts allowed */
add r12, r12, r12;
#ifdef DEBUG
@@ -417,7 +418,7 @@
addik r5, r1, 0; /* Arg 1: struct pt_regs *regs */
bralid r15, do_notify_resume; /* Handle any signals */
- addi r6, r0, 1; /* Arg 2: int in_syscall */
+ add r6, r30, r0; /* Arg 2: int in_syscall */
/* Finally, return to user state. */
1: set_bip; /* Ints masked for state restore */
@@ -464,6 +465,7 @@
add r3, r0, r0
C_ENTRY(sys_rt_sigreturn_wrapper):
+ addik r30, r0, 0 /* no restarts */
brid sys_rt_sigreturn /* Do real work */
addik r5, r1, 0; /* add user context as 1st arg */