[RFC 7/7] x86/unwind/64: Add support for the SYSENTER stack

[Andy Lutomirski <luto@kernel.org>]

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/stacktrace.h |  1 +
 arch/x86/kernel/dumpstack_32.c    |  3 +++
 arch/x86/kernel/dumpstack_64.c    | 23 +++++++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index 2e41c50ddf47..854f5cd141ed 100644
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -15,6 +15,7 @@ enum stack_type {
 	STACK_TYPE_TASK,
 	STACK_TYPE_IRQ,
 	STACK_TYPE_SOFTIRQ,
+	STACK_TYPE_SYSENTER,
 	STACK_TYPE_EXCEPTION,
 	STACK_TYPE_EXCEPTION_LAST = STACK_TYPE_EXCEPTION + N_EXCEPTION_STACKS-1,
 };
diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index 4f0481474903..0a04c7a9ecfc 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -25,6 +25,9 @@ const char *stack_type_name(enum stack_type type)
 	if (type == STACK_TYPE_SOFTIRQ)
 		return "SOFTIRQ";
 
+	if (type == STACK_TYPE_SYSENTER)
+		return "SYSENTER";
+
 	return NULL;
 }
 
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 225af4184f06..b9195ff7f1cf 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -36,6 +36,9 @@ const char *stack_type_name(enum stack_type type)
 	if (type == STACK_TYPE_IRQ)
 		return "IRQ";
 
+	if (type == STACK_TYPE_SYSENTER)
+		return "SYSENTER";
+
 	if (type >= STACK_TYPE_EXCEPTION && type <= STACK_TYPE_EXCEPTION_LAST)
 		return exception_stack_names[type - STACK_TYPE_EXCEPTION];
 
@@ -94,6 +97,23 @@ static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
 	return true;
 }
 
+static bool in_SYSENTER_stack(unsigned long *stack, struct stack_info *info)
+{
+	int cpu = smp_processor_id();
+	void *begin = &get_cpu_entry_area(cpu)->tss.SYSENTER_stack;
+	void *end   = begin + sizeof(cpu_tss.SYSENTER_stack);
+
+	if ((void *)stack < begin || (void *)stack >= end)
+		return false;
+
+	info->type	= STACK_TYPE_SYSENTER;
+	info->begin	= begin;
+	info->end	= end;
+	info->next_sp	= NULL;
+
+	return true;
+}
+
 int get_stack_info(unsigned long *stack, struct task_struct *task,
 		   struct stack_info *info, unsigned long *visit_mask)
 {
@@ -114,6 +134,9 @@ int get_stack_info(unsigned long *stack, struct task_struct *task,
 	if (in_irq_stack(stack, info))
 		goto recursion_check;
 
+	if (in_SYSENTER_stack(stack, info))
+		goto recursion_check;
+
 	goto unknown;
 
 recursion_check:
-- 
2.13.6