From 977e4be5eb714c48a67afc26a6c477f24130a1f2 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Sat, 20 Oct 2018 09:26:49 +0200 Subject: [PATCH] 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 dependency from . [ mingo: Improved the changelog a bit, added language explaining x86 borkage and sched.h change. ] Signed-off-by: Christophe Leroy Reviewed-by: Juergen Gross Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner 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 --- 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 #include #include +#include #include #include @@ -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 #include #include -#include #include #include #include -- 2.30.2