From: Joerg Roedel <jroedel@suse.de>
Date: Mon, 7 Sep 2020 15:15:45 +0200
Subject: x86/dumpstack/64: Add noinstr version of get_stack_info()
Git-commit: 6b27edd74a5e9669120f7bd0ae1f475d124c1042
Patch-mainline: v5.10-rc1
References: jsc#SLE-14337

The get_stack_info() functionality is needed in the entry code for the
#VC exception handler. Provide a version of it in the .text.noinstr
section which can be called safely from there.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-45-joro@8bytes.org
---
 arch/x86/include/asm/stacktrace.h |    2 ++
 arch/x86/kernel/dumpstack.c       |    1 +
 arch/x86/kernel/dumpstack_64.c    |   38 ++++++++++++++++++++++----------------
 arch/x86/mm/cpu_entry_area.c      |    1 +
 4 files changed, 26 insertions(+), 16 deletions(-)

--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -35,6 +35,8 @@ bool in_entry_stack(unsigned long *stack
 
 int get_stack_info(unsigned long *stack, struct task_struct *task,
 		   struct stack_info *info, unsigned long *visit_mask);
+bool get_stack_info_noinstr(unsigned long *stack, struct task_struct *task,
+			    struct stack_info *info);
 
 const char *stack_type_name(enum stack_type type);
 
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -46,6 +46,7 @@ bool in_task_stack(unsigned long *stack,
 	return true;
 }
 
+/* Called from get_stack_info_noinstr - so must be noinstr too */
 bool in_entry_stack(unsigned long *stack, struct stack_info *info)
 {
 	struct entry_stack *ss = cpu_entry_stack(smp_processor_id());
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -88,7 +88,7 @@ struct estack_pages estack_pages[CEA_EST
 	EPAGERANGE(VC2),
 };
 
-static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
+static __always_inline bool in_exception_stack(unsigned long *stack, struct stack_info *info)
 {
 	unsigned long begin, end, stk = (unsigned long)stack;
 	const struct estack_pages *ep;
@@ -129,7 +129,7 @@ static bool in_exception_stack(unsigned
 	return true;
 }
 
-static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
+static __always_inline bool in_irq_stack(unsigned long *stack, struct stack_info *info)
 {
 	unsigned long *end   = (unsigned long *)this_cpu_read(hardirq_stack_ptr);
 	unsigned long *begin = end - (IRQ_STACK_SIZE / sizeof(long));
@@ -154,32 +154,38 @@ static bool in_irq_stack(unsigned long *
 	return true;
 }
 
-int get_stack_info(unsigned long *stack, struct task_struct *task,
-		   struct stack_info *info, unsigned long *visit_mask)
+bool get_stack_info_noinstr(unsigned long *stack, struct task_struct *task,
+			    struct stack_info *info)
 {
-	if (!stack)
-		goto unknown;
-
-	task = task ? : current;
-
 	if (in_task_stack(stack, task, info))
-		goto recursion_check;
+		return true;
 
 	if (task != current)
-		goto unknown;
+		return false;
 
 	if (in_exception_stack(stack, info))
-		goto recursion_check;
+		return true;
 
 	if (in_irq_stack(stack, info))
-		goto recursion_check;
+		return true;
 
 	if (in_entry_stack(stack, info))
-		goto recursion_check;
+		return true;
+
+	return false;
+}
+
+int get_stack_info(unsigned long *stack, struct task_struct *task,
+		   struct stack_info *info, unsigned long *visit_mask)
+{
+	task = task ? : current;
 
-	goto unknown;
+	if (!stack)
+		goto unknown;
+
+	if (!get_stack_info_noinstr(stack, task, info))
+		goto unknown;
 
-recursion_check:
 	/*
 	 * Make sure we don't iterate through any given stack more than once.
 	 * If it comes up a second time then there's something wrong going on:
--- a/arch/x86/mm/cpu_entry_area.c
+++ b/arch/x86/mm/cpu_entry_area.c
@@ -17,6 +17,7 @@ static DEFINE_PER_CPU_PAGE_ALIGNED(struc
 DEFINE_PER_CPU(struct cea_exception_stacks*, cea_exception_stacks);
 #endif
 
+/* Is called from entry code, so must be noinstr */
 struct cpu_entry_area *get_cpu_entry_area(int cpu)
 {
 	unsigned long va = CPU_ENTRY_AREA_PER_CPU + cpu * CPU_ENTRY_AREA_SIZE;