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authorChristophe Leroy <christophe.leroy@c-s.fr>2018-10-20 09:26:49 +0200
committerIngo Molnar <mingo@kernel.org>2018-10-22 04:07:24 +0200
commit977e4be5eb714c48a67afc26a6c477f24130a1f2 (patch)
tree6efdd00663fdbc06815a8412d76fbd8568257562
parent162041425193602b15774c61740ad8e7dc157df3 (diff)
downloadlinux-977e4be5eb714c48a67afc26a6c477f24130a1f2.tar.bz2
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>
-rw-r--r--arch/x86/xen/smp_pv.c2
-rw-r--r--kernel/sched/idle.c15
-rw-r--r--kernel/sched/sched.h1
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>