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-nommu.S b/arch/microblaze/kernel/entry-nommu.S
index 29a05d6..96f97f8 100644
--- a/arch/microblaze/kernel/entry-nommu.S
+++ b/arch/microblaze/kernel/entry-nommu.S
@@ -280,6 +280,7 @@
/* 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 */
+ addik r30, r0, 1 /* restarts allowed */
add r12, r12, r12
lwi r12, r12, sys_call_table /* Get function pointer */
addik r15, r0, ret_to_user-8 /* set return address */
@@ -369,6 +370,7 @@
bralid r15, send_sig
add r7, r0, r0 /* 3rd param zero */
+ addik r30, r0, 1 /* restarts allowed ??? */
/* Restore r3/r4 to work around how ret_to_user works */
lwi r3, r1, PT_R3
lwi r4, r1, PT_R4
@@ -492,7 +494,7 @@
nop
1: andi r11, r19, _TIF_SIGPENDING | _TIF_NOTIFY_RESUME
beqi r11, no_work_pending
- addk r5, r1, r0
+ addk r5, r30, r0
bralid r15, do_notify_resume
addik r6, r0, 1
bri no_work_pending
@@ -562,6 +564,7 @@
nop
sys_rt_sigreturn_wrapper:
+ addk r30, r0, r0 /* no restarts for this one */
brid sys_rt_sigreturn
addk r5, r1, r0