[PATCH v6 47/76] x86/dumpstack/64: Add noinstr version of get_stack_info()

[Joerg Roedel]

From: Joerg Roedel <jroedel@xxxxxxx>

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@xxxxxxx>
Link: https://lore.kernel.org/r/20200724160336.5435-47-joro@xxxxxxxxxx
---
 arch/x86/include/asm/stacktrace.h |  2 ++
 arch/x86/kernel/dumpstack.c       |  7 +++---
 arch/x86/kernel/dumpstack_64.c    | 39 ++++++++++++++++++-------------
 arch/x86/mm/cpu_entry_area.c      |  3 ++-
 4 files changed, 31 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index 5ae5a68e469d..49600643faba 100644
--- 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, struct stack_info *info);
 
 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);
 
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 48ce44576947..74147f7b3d82 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -29,8 +29,8 @@ static int die_counter;
 
 static struct pt_regs exec_summary_regs;
 
-bool in_task_stack(unsigned long *stack, struct task_struct *task,
-		   struct stack_info *info)
+bool noinstr in_task_stack(unsigned long *stack, struct task_struct *task,
+			   struct stack_info *info)
 {
 	unsigned long *begin = task_stack_page(task);
 	unsigned long *end   = task_stack_page(task) + THREAD_SIZE;
@@ -46,7 +46,8 @@ bool in_task_stack(unsigned long *stack, struct task_struct *task,
 	return true;
 }
 
-bool in_entry_stack(unsigned long *stack, struct stack_info *info)
+/* Called from get_stack_info_noinstr - so must be noinstr too */
+bool noinstr in_entry_stack(unsigned long *stack, struct stack_info *info)
 {
 	struct entry_stack *ss = cpu_entry_stack(smp_processor_id());
 
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index c49cf594714b..5a85730eb0ca 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -85,7 +85,7 @@ struct estack_pages estack_pages[CEA_ESTACK_PAGES] ____cacheline_aligned = {
 	EPAGERANGE(VC2),
 };
 
-static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
+static bool __always_inline in_exception_stack(unsigned long *stack, struct stack_info *info)
 {
 	unsigned long begin, end, stk = (unsigned long)stack;
 	const struct estack_pages *ep;
@@ -126,7 +126,7 @@ static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
 	return true;
 }
 
-static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
+static bool __always_inline 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));
@@ -151,32 +151,38 @@ static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
 	return true;
 }
 
-int get_stack_info(unsigned long *stack, struct task_struct *task,
-		   struct stack_info *info, unsigned long *visit_mask)
+bool noinstr 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;
 
-	goto unknown;
+	return false;
+}
+
+int get_stack_info(unsigned long *stack, struct task_struct *task,
+		   struct stack_info *info, unsigned long *visit_mask)
+{
+	task = task ? : current;
+
+	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:
@@ -196,4 +202,5 @@ int get_stack_info(unsigned long *stack, struct task_struct *task,
 unknown:
 	info->type = STACK_TYPE_UNKNOWN;
 	return -EINVAL;
+
 }
diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c
index 770b613790b3..f5e1e60c9095 100644
--- a/arch/x86/mm/cpu_entry_area.c
+++ b/arch/x86/mm/cpu_entry_area.c
@@ -21,7 +21,8 @@ DEFINE_PER_CPU(struct cea_exception_stacks*, cea_exception_stacks);
 DECLARE_PER_CPU_PAGE_ALIGNED(struct doublefault_stack, doublefault_stack);
 #endif
 
-struct cpu_entry_area *get_cpu_entry_area(int cpu)
+/* Is called from entry code, so must be noinstr */
+noinstr struct cpu_entry_area *get_cpu_entry_area(int cpu)
 {
 	unsigned long va = CPU_ENTRY_AREA_PER_CPU + cpu * CPU_ENTRY_AREA_SIZE;
 	BUILD_BUG_ON(sizeof(struct cpu_entry_area) % PAGE_SIZE != 0);
-- 
2.28.0