Commit-ID: 977e4be5eb714c48a67afc26a6c477f24130a1f2
Gitweb: https://git.kernel.org/tip/977e4be5eb714c48a67afc26a6c477f24130a1f2
Author: Christophe Leroy <[email protected]>
AuthorDate: Sat, 20 Oct 2018 09:26:49 +0200
Committer: Ingo Molnar <[email protected]>
CommitDate: Mon, 22 Oct 2018 04:07:24 +0200
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 <[email protected]>
Reviewed-by: Juergen Gross <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link:
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86/xen/smp_pv.c | 2 ++
kernel/sched/idle.c | 15 ---------------
kernel/sched/sched.h | 1 -
3 files changed, 2 insertions(+), 16 deletions(-)
diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
index e3b18ad49889..145506f9fdbe 100644
--- a/arch/x86/xen/smp_pv.c
+++ b/arch/x86/xen/smp_pv.c
@@ -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);
}
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 16f84142f2f4..f5516bae0c1b 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -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)
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>
