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x86/stackprotector: Remove the call to boot_init_stack_canary() from cpu_startup_entry() 

The following commit:

  d7880812b3 ("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>
This commit is contained in:
Christophe Leroy 2018-10-20 09:26:49 +02:00 committed by Ingo Molnar
parent 1620414251
commit 977e4be5eb
3 changed files with 2 additions and 16 deletions
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2
arch/x86/xen/smp_pv.c
View File

@ -22,6 +22,7 @@
#include <linux/tick.h>
#include <linux/nmi.h>
#include <linux/cpuhotplug.h>
#include <linux/stackprotector.h>
#include <asm/paravirt.h>
#include <asm/desc.h>
@ -88,6 +89,7 @@ static void cpu_bringup(void)
asmlinkage __visible void cpu_bringup_and_idle(void)
{
cpu_bringup();
boot_init_stack_canary();
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}

15
kernel/sched/idle.c
View File

@ -347,21 +347,6 @@ EXPORT_SYMBOL_GPL(play_idle);
void cpu_startup_entry(enum cpuhp_state state)
{
/*
* This #ifdef needs to die, but it's too late in the cycle to
* make this generic (ARM and SH have never invoked the canary
* init for the non boot CPUs!). Will be fixed in 3.11
*/
#ifdef CONFIG_X86
/*
* If we're the non-boot CPU, nothing set the stack canary up
* for us. The boot CPU already has it initialized but no harm
* in doing it again. This is a good place for updating it, as
* we wont ever return from this function (so the invalid
* canaries already on the stack wont ever trigger).
*/
boot_init_stack_canary();
#endif
arch_cpu_idle_prepare();
cpuhp_online_idle(state);
while (1)

1
kernel/sched/sched.h
View File

@ -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>