[PATCH 1/2] arm64: Introduce current_stack_type

[Laura Abbott]

In preparation for enabling the stackleak plugin on arm64,
we need a way to get the bounds of the current stack.
Introduce a new primitive current_stack_type which is similar
to x86's get_stack_info. Utilize that to rework
on_accessible_stack slightly as well.

Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx>
---
So this did end up looking quite a bit like get_stack_info but I didn't
really see the need to integrate this more than this. I do think
actually enumerating the types makes things a bit cleaner.
---
 arch/arm64/include/asm/sdei.h       |  8 ++-
 arch/arm64/include/asm/stacktrace.h | 94 ++++++++++++++++++++++++-----
 arch/arm64/kernel/ptrace.c          |  2 +-
 arch/arm64/kernel/sdei.c            | 21 ++++++-
 4 files changed, 103 insertions(+), 22 deletions(-)

diff --git a/arch/arm64/include/asm/sdei.h b/arch/arm64/include/asm/sdei.h
index e073e6886685..34f7b203845b 100644
--- a/arch/arm64/include/asm/sdei.h
+++ b/arch/arm64/include/asm/sdei.h
@@ -40,15 +40,17 @@ asmlinkage unsigned long __sdei_handler(struct pt_regs *regs,
 unsigned long sdei_arch_get_entry_point(int conduit);
 #define sdei_arch_get_entry_point(x)	sdei_arch_get_entry_point(x)
 
-bool _on_sdei_stack(unsigned long sp);
-static inline bool on_sdei_stack(unsigned long sp)
+bool _on_sdei_stack(unsigned long sp, unsigned long *, unsigned long *);
+static inline bool on_sdei_stack(unsigned long sp,
+				unsigned long *stack_low,
+				unsigned long *stack_high)
 {
 	if (!IS_ENABLED(CONFIG_VMAP_STACK))
 		return false;
 	if (!IS_ENABLED(CONFIG_ARM_SDE_INTERFACE))
 		return false;
 	if (in_nmi())
-		return _on_sdei_stack(sp);
+		return _on_sdei_stack(sp, stack_low, stack_high);
 
 	return false;
 }
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 902f9edacbea..9855a0425e64 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -39,7 +39,9 @@ extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk);
 
 DECLARE_PER_CPU(unsigned long *, irq_stack_ptr);
 
-static inline bool on_irq_stack(unsigned long sp)
+static inline bool on_irq_stack(unsigned long sp,
+				unsigned long *stack_low,
+				unsigned long *stack_high)
 {
 	unsigned long low = (unsigned long)raw_cpu_read(irq_stack_ptr);
 	unsigned long high = low + IRQ_STACK_SIZE;
@@ -47,47 +49,109 @@ static inline bool on_irq_stack(unsigned long sp)
 	if (!low)
 		return false;
 
-	return (low <= sp && sp < high);
+	if (sp < low || sp >= high)
+		return false;
+
+	if (stack_low && stack_high) {
+		*stack_low = low;
+		*stack_high = high;
+	}
+
+	return true;
 }
 
-static inline bool on_task_stack(struct task_struct *tsk, unsigned long sp)
+static inline bool on_task_stack(struct task_struct *tsk, unsigned long sp,
+				unsigned long *stack_low,
+				unsigned long *stack_high)
 {
 	unsigned long low = (unsigned long)task_stack_page(tsk);
 	unsigned long high = low + THREAD_SIZE;
 
-	return (low <= sp && sp < high);
+	if (sp < low || sp >= high)
+		return false;
+
+	if (stack_low && stack_high) {
+		*stack_low = low;
+		*stack_high = high;
+	}
+
+	return true;
 }
 
 #ifdef CONFIG_VMAP_STACK
 DECLARE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack);
 
-static inline bool on_overflow_stack(unsigned long sp)
+static inline bool on_overflow_stack(unsigned long sp,
+				unsigned long *stack_low,
+				unsigned long *stack_high)
 {
 	unsigned long low = (unsigned long)raw_cpu_ptr(overflow_stack);
 	unsigned long high = low + OVERFLOW_STACK_SIZE;
 
-	return (low <= sp && sp < high);
+	if (sp < low || sp >= high)
+		return false;
+
+	if (stack_low && stack_high) {
+		*stack_low = low;
+		*stack_high = high;
+	}
+
+	return true;
 }
 #else
-static inline bool on_overflow_stack(unsigned long sp) { return false; }
+static inline bool on_overflow_stack(unsigned long sp,
+			unsigned long *stack_low,
+			unsigned long *stack_high) { return false; }
 #endif
 
+enum stack_type {
+	STACK_TYPE_UNKNOWN,
+	STACK_TYPE_TASK,
+	STACK_TYPE_IRQ,
+	STACK_TYPE_OVERFLOW,
+	STACK_TYPE_SDEI,
+};
+
+static inline enum stack_type current_stack_type(struct task_struct *tsk,
+						unsigned long sp,
+						unsigned long *stack_low,
+						unsigned long *stack_high)
+{
+	if (on_task_stack(tsk, sp, stack_low, stack_high))
+		return STACK_TYPE_TASK;
+	if (on_irq_stack(sp, stack_low, stack_high))
+		return STACK_TYPE_IRQ;
+	if (on_overflow_stack(sp, stack_low, stack_high))
+		return STACK_TYPE_OVERFLOW;
+	if (on_sdei_stack(sp, stack_low, stack_high))
+		return STACK_TYPE_SDEI;
+	return STACK_TYPE_UNKNOWN;
+}
+
 /*
  * We can only safely access per-cpu stacks from current in a non-preemptible
  * context.
  */
 static inline bool on_accessible_stack(struct task_struct *tsk, unsigned long sp)
 {
-	if (on_task_stack(tsk, sp))
+	enum stack_type type;
+	unsigned long low, high;
+
+	type = current_stack_type(tsk, sp, &low, &high);
+
+	switch (type) {
+	case STACK_TYPE_TASK:
 		return true;
-	if (tsk != current || preemptible())
+	case STACK_TYPE_IRQ:
+	case STACK_TYPE_OVERFLOW:
+	case STACK_TYPE_SDEI:
+		if (tsk != current || preemptible())
+			return false;
+		else
+			return true;
+	case STACK_TYPE_UNKNOWN:
 		return false;
-	if (on_irq_stack(sp))
-		return true;
-	if (on_overflow_stack(sp))
-		return true;
-	if (on_sdei_stack(sp))
-		return true;
+	}
 
 	return false;
 }
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 5c338ce5a7fa..a6b3a2be7561 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -132,7 +132,7 @@ static bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
 {
 	return ((addr & ~(THREAD_SIZE - 1))  ==
 		(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1))) ||
-		on_irq_stack(addr);
+		on_irq_stack(addr, NULL, NULL);
 }
 
 /**
diff --git a/arch/arm64/kernel/sdei.c b/arch/arm64/kernel/sdei.c
index 6b8d90d5ceae..8e18913a53fd 100644
--- a/arch/arm64/kernel/sdei.c
+++ b/arch/arm64/kernel/sdei.c
@@ -88,7 +88,9 @@ static int init_sdei_stacks(void)
 	return err;
 }
 
-bool _on_sdei_stack(unsigned long sp)
+bool _on_sdei_stack(unsigned long sp,
+		unsigned long *stack_low,
+		unsigned long *stack_high)
 {
 	unsigned long low, high;
 
@@ -98,13 +100,26 @@ bool _on_sdei_stack(unsigned long sp)
 	low = (unsigned long)raw_cpu_read(sdei_stack_critical_ptr);
 	high = low + SDEI_STACK_SIZE;
 
-	if (low <= sp && sp < high)
+	if (low <= sp && sp < high) {
+		if (stack_low && stack_high) {
+			*stack_low = low;
+			*stack_high = high;
+		}
 		return true;
+	}
 
 	low = (unsigned long)raw_cpu_read(sdei_stack_normal_ptr);
 	high = low + SDEI_STACK_SIZE;
 
-	return (low <= sp && sp < high);
+	if (low <= sp && sp < high) {
+		if (stack_low && stack_high) {
+			*stack_low = low;
+			*stack_high = high;
+		}
+		return true;
+	}
+
+	return false;
 }
 
 unsigned long sdei_arch_get_entry_point(int conduit)
-- 
2.17.1