From 977e4be5eb714c48a67afc26a6c477f24130a1f2 Mon Sep 17 00:00:00 2001
From: Christophe Leroy <christophe.leroy@c-s.fr>
Date: Sat, 20 Oct 2018 09:26:49 +0200
Subject: x86/stackprotector: Remove the call to boot_init_stack_canary() from
 cpu_startup_entry()

The following commit:

  d7880812b359 ("idle: Add the stack canary init to cpu_startup_entry()")

... added an x86 specific boot_init_stack_canary() call to the generic
cpu_startup_entry() as a temporary hack, with the intention to remove
the #ifdef CONFIG_X86 later.

More than 5 years later let's finally realize that plan! :-)

While implementing stack protector support for PowerPC, we found
that calling boot_init_stack_canary() is also needed for PowerPC
which uses per task (TLS) stack canary like the X86.

However, calling boot_init_stack_canary() would break architectures
using a global stack canary (ARM, SH, MIPS and XTENSA).

Instead of modifying the #ifdef CONFIG_X86 to an even messier:

   #if defined(CONFIG_X86) || defined(CONFIG_PPC)

PowerPC implemented the call to boot_init_stack_canary() in the function
calling cpu_startup_entry().

Let's try the same cleanup on the x86 side as well.

On x86 we have two functions calling cpu_startup_entry():

 - start_secondary()
 - cpu_bringup_and_idle()

start_secondary() already calls boot_init_stack_canary(), so
it's good, and this patch adds the call to boot_init_stack_canary()
in cpu_bringup_and_idle().

I.e. now x86 catches up to the rest of the world and the ugly init
sequence in init/main.c can be removed from cpu_startup_entry().

As a final benefit we can also remove the <linux/stackprotector.h>
dependency from <linux/sched.h>.

[ mingo: Improved the changelog a bit, added language explaining x86 borkage and sched.h change. ]
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/20181020072649.5B59310483E@pc16082vm.idsi0.si.c-s.fr
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/sched.h | 1 -
 1 file changed, 1 deletion(-)

(limited to 'kernel/sched/sched.h')

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 4a2e8cae63c4..5b00a816a4b3 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -56,7 +56,6 @@
 #include <linux/profile.h>
 #include <linux/rcupdate_wait.h>
 #include <linux/security.h>
-#include <linux/stackprotector.h>
 #include <linux/stop_machine.h>
 #include <linux/suspend.h>
 #include <linux/swait.h>
-- 
cgit