nmi: backtrace: Allow runtime arch specific override

maillist inclusion
category: feature
bugzilla: 49593
CVE: NA
Reference: https://www.spinics.net/lists/arm-kernel/msg851005.html

-------------------------------------------------

Add a boolean return to arch_trigger_cpumask_backtrace() to support a
use-case where a particular architecture detects at runtime if it supports
NMI backtrace or it would like to fallback to default implementation using
SMP cross-calls.

Currently such an architecture example is arm64 supporting pseudo NMIs
feature which is only available on platforms which have support for GICv3
or later version.
Signed-off-by: NSumit Garg <sumit.garg@linaro.org>
Signed-off-by: NWei Li <liwei391@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/arm/include/asm/irq.h

@@ -31,7 +31,7 @@ void handle_IRQ(unsigned int, struct pt_regs *);
 void init_IRQ(void);
 
 #ifdef CONFIG_SMP
-extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask,
+extern bool arch_trigger_cpumask_backtrace(const cpumask_t *mask,
 					   bool exclude_self);
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 #endif

arch/arm/kernel/smp.c

@@ -856,7 +856,8 @@ static void raise_nmi(cpumask_t *mask)
 	__ipi_send_mask(ipi_desc[IPI_CPU_BACKTRACE], mask);
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
 	nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_nmi);
+	return true;
 }

arch/mips/include/asm/irq.h

@@ -78,7 +78,7 @@ extern int cp0_fdc_irq;
 
 extern int get_c0_fdc_int(void);
 
-void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
+bool arch_trigger_cpumask_backtrace(const struct cpumask *mask,
 				    bool exclude_self);
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 

arch/mips/kernel/process.c

@@ -735,9 +735,10 @@ static void raise_backtrace(cpumask_t *mask)
 	}
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
 	nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace);
+	return true;
 }
 
 int mips_get_process_fp_mode(struct task_struct *task)

arch/powerpc/include/asm/nmi.h

@@ -9,7 +9,7 @@ static inline void arch_touch_nmi_watchdog(void) {}
 #endif
 
 #if defined(CONFIG_NMI_IPI) && defined(CONFIG_STACKTRACE)
-extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask,
+extern bool arch_trigger_cpumask_backtrace(const cpumask_t *mask,
 					   bool exclude_self);
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 #endif

arch/powerpc/kernel/stacktrace.c

@@ -264,8 +264,9 @@ static void raise_backtrace_ipi(cpumask_t *mask)
 	}
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
 	nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
+	return true;
 }
 #endif /* defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) */

arch/sparc/include/asm/irq_64.h

@@ -87,7 +87,7 @@ static inline unsigned long get_softint(void)
 	return retval;
 }
 
-void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
+bool arch_trigger_cpumask_backtrace(const struct cpumask *mask,
 				    bool exclude_self);
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
 

arch/sparc/kernel/process_64.c

@@ -248,7 +248,7 @@ static void __global_reg_poll(struct global_reg_snapshot *gp)
 	}
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
 	struct thread_info *tp = current_thread_info();
 	struct pt_regs *regs = get_irq_regs();
@@ -303,6 +303,8 @@ void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 	memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));
 
 	spin_unlock_irqrestore(&global_cpu_snapshot_lock, flags);
+
+	return true;
 }
 
 #ifdef CONFIG_MAGIC_SYSRQ

arch/x86/include/asm/irq.h

@@ -47,7 +47,7 @@ extern void init_ISA_irqs(void);
 extern void __init init_IRQ(void);
 
 #ifdef CONFIG_X86_LOCAL_APIC
-void arch_trigger_cpumask_backtrace(const struct cpumask *mask,
+bool arch_trigger_cpumask_backtrace(const struct cpumask *mask,
 				    bool exclude_self);
 
 #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace

arch/x86/kernel/apic/hw_nmi.c

@@ -34,10 +34,11 @@ static void nmi_raise_cpu_backtrace(cpumask_t *mask)
 	apic->send_IPI_mask(mask, NMI_VECTOR);
 }
 
-void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
+bool arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
 	nmi_trigger_cpumask_backtrace(mask, exclude_self,
 				      nmi_raise_cpu_backtrace);
+	return true;
 }
 
 static int nmi_cpu_backtrace_handler(unsigned int cmd, struct pt_regs *regs)

include/linux/nmi.h

@@ -163,26 +163,22 @@ static inline void touch_nmi_watchdog(void)
 #ifdef arch_trigger_cpumask_backtrace
 static inline bool trigger_all_cpu_backtrace(void)
 {
-	arch_trigger_cpumask_backtrace(cpu_online_mask, false);
-	return true;
+	return arch_trigger_cpumask_backtrace(cpu_online_mask, false);
 }
 
 static inline bool trigger_allbutself_cpu_backtrace(void)
 {
-	arch_trigger_cpumask_backtrace(cpu_online_mask, true);
-	return true;
+	return arch_trigger_cpumask_backtrace(cpu_online_mask, true);
 }
 
 static inline bool trigger_cpumask_backtrace(struct cpumask *mask)
 {
-	arch_trigger_cpumask_backtrace(mask, false);
-	return true;
+	return arch_trigger_cpumask_backtrace(mask, false);
 }
 
 static inline bool trigger_single_cpu_backtrace(int cpu)
 {
-	arch_trigger_cpumask_backtrace(cpumask_of(cpu), false);
-	return true;
+	return arch_trigger_cpumask_backtrace(cpumask_of(cpu), false);
 }
 
 /* generic implementation */