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Date: Fri, 17 Apr 2020 09:57:39 +0200
From: Borislav Petkov <bp@...en8.de>
To: Sergei Trofimovich <slyfox@...too.org>
Cc: Michael Matz <matz@...e.de>, Jakub Jelinek <jakub@...hat.com>,
linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>, x86@...nel.org
Subject: Re: [PATCH v2] x86: fix early boot crash on gcc-10
On Wed, Apr 15, 2020 at 11:19:30PM +0100, Sergei Trofimovich wrote:
> Ah, that makes sense. Borislav, should I send a fix forward against
> x86 tree to move -fno-stack-protector as it was in v1 patch?
> Or you'll revert v2 and apply v1 ~as is? Or should I send those myself?
Yeah, Peter and I have been discussing something like the below
yesterday. I don't like the additional exports too much but would
disable stack protector only for the one function...
---
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 3bcf27caf6c9..e258a6a21674 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -990,4 +990,8 @@ enum mds_mitigations {
MDS_MITIGATION_VMWERV,
};
+extern int enable_start_cpu0;
+void smp_callin(void);
+void notrace start_secondary(void *unused);
+
#endif /* _ASM_X86_PROCESSOR_H */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 92e1261ec4ec..7130ca9edc50 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -87,7 +87,13 @@ obj-$(CONFIG_PCI) += early-quirks.o
apm-y := apm_32.o
obj-$(CONFIG_APM) += apm.o
obj-$(CONFIG_SMP) += smp.o
-obj-$(CONFIG_SMP) += smpboot.o
+
+nostackprot := $(call cc-option, -fno-stack-protector)
+CFLAGS_smpboot_aux.o := $(nostackprot)
+
+smpboot_all-y := smpboot.o smpboot_aux.o
+obj-$(CONFIG_SMP) += smpboot_all.o
+
obj-$(CONFIG_X86_TSC) += tsc_sync.o
obj-$(CONFIG_SMP) += setup_percpu.o
obj-$(CONFIG_X86_MPPARSE) += mpparse.o
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 3b9bf8c7e29d..1ce6280999f9 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -153,7 +153,7 @@ static void init_freq_invariance(void);
* Report back to the Boot Processor during boot time or to the caller processor
* during CPU online.
*/
-static void smp_callin(void)
+void smp_callin(void)
{
int cpuid;
@@ -208,65 +208,7 @@ static void smp_callin(void)
}
static int cpu0_logical_apicid;
-static int enable_start_cpu0;
-/*
- * Activate a secondary processor.
- */
-static void notrace start_secondary(void *unused)
-{
- /*
- * Don't put *anything* except direct CPU state initialization
- * before cpu_init(), SMP booting is too fragile that we want to
- * limit the things done here to the most necessary things.
- */
- cr4_init();
-
-#ifdef CONFIG_X86_32
- /* switch away from the initial page table */
- load_cr3(swapper_pg_dir);
- __flush_tlb_all();
-#endif
- load_current_idt();
- cpu_init();
- x86_cpuinit.early_percpu_clock_init();
- preempt_disable();
- smp_callin();
-
- enable_start_cpu0 = 0;
-
- /* otherwise gcc will move up smp_processor_id before the cpu_init */
- barrier();
- /*
- * Check TSC synchronization with the boot CPU:
- */
- check_tsc_sync_target();
-
- speculative_store_bypass_ht_init();
-
- /*
- * Lock vector_lock, set CPU online and bring the vector
- * allocator online. Online must be set with vector_lock held
- * to prevent a concurrent irq setup/teardown from seeing a
- * half valid vector space.
- */
- lock_vector_lock();
- set_cpu_online(smp_processor_id(), true);
- lapic_online();
- unlock_vector_lock();
- cpu_set_state_online(smp_processor_id());
- x86_platform.nmi_init();
-
- /* enable local interrupts */
- local_irq_enable();
-
- /* to prevent fake stack check failure in clock setup */
- boot_init_stack_canary();
-
- x86_cpuinit.setup_percpu_clockev();
-
- wmb();
- cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
-}
+int enable_start_cpu0;
/**
* topology_is_primary_thread - Check whether CPU is the primary SMT thread
diff --git a/arch/x86/kernel/smpboot_aux.c b/arch/x86/kernel/smpboot_aux.c
new file mode 100644
index 000000000000..8863fde54eed
--- /dev/null
+++ b/arch/x86/kernel/smpboot_aux.c
@@ -0,0 +1,70 @@
+#include <linux/cpu.h>
+
+#include <asm/desc.h>
+#include <asm/hw_irq.h>
+#include <asm/spec-ctrl.h>
+#include <asm/processor.h>
+#include <asm/stackprotector.h>
+
+/*
+ * Activate a secondary processor.
+ *
+ * Note: boot_init_stack_canary() sets up the canary value so omit the stack
+ * canary creation for this function only by keeping it in a separate
+ * compilation unit.
+ */
+void notrace start_secondary(void *unused)
+{
+ /*
+ * Don't put *anything* except direct CPU state initialization
+ * before cpu_init(), SMP booting is too fragile that we want to
+ * limit the things done here to the most necessary things.
+ */
+ cr4_init();
+
+#ifdef CONFIG_X86_32
+ /* switch away from the initial page table */
+ load_cr3(swapper_pg_dir);
+ __flush_tlb_all();
+#endif
+ load_current_idt();
+ cpu_init();
+ x86_cpuinit.early_percpu_clock_init();
+ preempt_disable();
+ smp_callin();
+
+ enable_start_cpu0 = 0;
+
+ /* otherwise gcc will move up smp_processor_id before the cpu_init */
+ barrier();
+ /*
+ * Check TSC synchronization with the boot CPU:
+ */
+ check_tsc_sync_target();
+
+ speculative_store_bypass_ht_init();
+
+ /*
+ * Lock vector_lock, set CPU online and bring the vector
+ * allocator online. Online must be set with vector_lock held
+ * to prevent a concurrent irq setup/teardown from seeing a
+ * half valid vector space.
+ */
+ lock_vector_lock();
+ set_cpu_online(smp_processor_id(), true);
+ lapic_online();
+ unlock_vector_lock();
+ cpu_set_state_online(smp_processor_id());
+ x86_platform.nmi_init();
+
+ /* enable local interrupts */
+ local_irq_enable();
+
+ /* to prevent fake stack check failure in clock setup */
+ boot_init_stack_canary();
+
+ x86_cpuinit.setup_percpu_clockev();
+
+ wmb();
+ cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
+}
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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