1 files changed, 103 insertions, 25 deletions

diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index ff467b98c3e3..b41b6255751c 100644
--- a/arch/riscv/kernel/stacktrace.c
+++ b/arch/riscv/kernel/stacktrace.c
@@ -14,23 +14,53 @@
 
 #include <asm/stacktrace.h>
 
-register unsigned long sp_in_global __asm__("sp");
-
 #ifdef CONFIG_FRAME_POINTER
 
+/*
+ * This disables KASAN checking when reading a value from another task's stack,
+ * since the other task could be running on another CPU and could have poisoned
+ * the stack in the meantime.
+ */
+#define READ_ONCE_TASK_STACK(task, x)			\
+({							\
+	unsigned long val;				\
+	unsigned long addr = x;				\
+	if ((task) == current)				\
+		val = READ_ONCE(addr);			\
+	else						\
+		val = READ_ONCE_NOCHECK(addr);		\
+	val;						\
+})
+
+extern asmlinkage void handle_exception(void);
+extern unsigned long ret_from_exception_end;
+
+static inline int fp_is_valid(unsigned long fp, unsigned long sp)
+{
+	unsigned long low, high;
+
+	low = sp + sizeof(struct stackframe);
+	high = ALIGN(sp, THREAD_SIZE);
+
+	return !(fp < low || fp > high || fp & 0x07);
+}
+
 void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
 			     bool (*fn)(void *, unsigned long), void *arg)
 {
 	unsigned long fp, sp, pc;
+	int graph_idx = 0;
+	int level = 0;
 
 	if (regs) {
 		fp = frame_pointer(regs);
 		sp = user_stack_pointer(regs);
 		pc = instruction_pointer(regs);
-	} else if (task == current) {
-		fp = (unsigned long)__builtin_frame_address(1);
-		sp = (unsigned long)__builtin_frame_address(0);
-		pc = (unsigned long)__builtin_return_address(0);
+	} else if (task == NULL || task == current) {
+		fp = (unsigned long)__builtin_frame_address(0);
+		sp = current_stack_pointer;
+		pc = (unsigned long)walk_stackframe;
+		level = -1;
 	} else {
 		/* task blocked in __switch_to */
 		fp = task->thread.s[0];
@@ -39,27 +69,34 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
 	}
 
 	for (;;) {
-		unsigned long low, high;
 		struct stackframe *frame;
 
-		if (unlikely(!__kernel_text_address(pc) || !fn(arg, pc)))
+		if (unlikely(!__kernel_text_address(pc) || (level++ >= 0 && !fn(arg, pc))))
 			break;
 
-		/* Validate frame pointer */
-		low = sp + sizeof(struct stackframe);
-		high = ALIGN(sp, THREAD_SIZE);
-		if (unlikely(fp < low || fp > high || fp & 0x7))
+		if (unlikely(!fp_is_valid(fp, sp)))
 			break;
+
 		/* Unwind stack frame */
 		frame = (struct stackframe *)fp - 1;
 		sp = fp;
-		if (regs && (regs->epc == pc) && (frame->fp & 0x7)) {
+		if (regs && (regs->epc == pc) && fp_is_valid(frame->ra, sp)) {
+			/* We hit function where ra is not saved on the stack */
 			fp = frame->ra;
 			pc = regs->ra;
 		} else {
-			fp = frame->fp;
-			pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
-						   (unsigned long *)(fp - 8));
+			fp = READ_ONCE_TASK_STACK(task, frame->fp);
+			pc = READ_ONCE_TASK_STACK(task, frame->ra);
+			pc = ftrace_graph_ret_addr(current, &graph_idx, pc,
+						   &frame->ra);
+			if (pc >= (unsigned long)handle_exception &&
+			    pc < (unsigned long)&ret_from_exception_end) {
+				if (unlikely(!fn(arg, pc)))
+					break;
+
+				pc = ((struct pt_regs *)sp)->epc;
+				fp = ((struct pt_regs *)sp)->s0;
+			}
 		}
 
 	}
@@ -77,7 +114,7 @@ void notrace walk_stackframe(struct task_struct *task,
 		sp = user_stack_pointer(regs);
 		pc = instruction_pointer(regs);
 	} else if (task == NULL || task == current) {
-		sp = sp_in_global;
+		sp = current_stack_pointer;
 		pc = (unsigned long)walk_stackframe;
 	} else {
 		/* task blocked in __switch_to */
@@ -92,7 +129,7 @@ void notrace walk_stackframe(struct task_struct *task,
 	while (!kstack_end(ksp)) {
 		if (__kernel_text_address(pc) && unlikely(!fn(arg, pc)))
 			break;
-		pc = (*ksp++) - 0x4;
+		pc = READ_ONCE_NOCHECK(*ksp++) - 0x4;
 	}
 }
 
@@ -128,21 +165,62 @@ static bool save_wchan(void *arg, unsigned long pc)
 	return true;
 }
 
-unsigned long get_wchan(struct task_struct *task)
+unsigned long __get_wchan(struct task_struct *task)
 {
 	unsigned long pc = 0;
 
-	if (likely(task && task != current && !task_is_running(task)))
-		walk_stackframe(task, NULL, save_wchan, &pc);
+	if (!try_get_task_stack(task))
+		return 0;
+	walk_stackframe(task, NULL, save_wchan, &pc);
+	put_task_stack(task);
 	return pc;
 }
 
-#ifdef CONFIG_STACKTRACE
-
-noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
+noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
 		     struct task_struct *task, struct pt_regs *regs)
 {
 	walk_stackframe(task, regs, consume_entry, cookie);
 }
 
-#endif /* CONFIG_STACKTRACE */
+/*
+ * Get the return address for a single stackframe and return a pointer to the
+ * next frame tail.
+ */
+static unsigned long unwind_user_frame(stack_trace_consume_fn consume_entry,
+				       void *cookie, unsigned long fp,
+				       unsigned long reg_ra)
+{
+	struct stackframe buftail;
+	unsigned long ra = 0;
+	unsigned long __user *user_frame_tail =
+		(unsigned long __user *)(fp - sizeof(struct stackframe));
+
+	/* Check accessibility of one struct frame_tail beyond */
+	if (!access_ok(user_frame_tail, sizeof(buftail)))
+		return 0;
+	if (__copy_from_user_inatomic(&buftail, user_frame_tail,
+				      sizeof(buftail)))
+		return 0;
+
+	ra = reg_ra ? : buftail.ra;
+
+	fp = buftail.fp;
+	if (!ra || !consume_entry(cookie, ra))
+		return 0;
+
+	return fp;
+}
+
+void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
+			  const struct pt_regs *regs)
+{
+	unsigned long fp = 0;
+
+	fp = regs->s0;
+	if (!consume_entry(cookie, regs->epc))
+		return;
+
+	fp = unwind_user_frame(consume_entry, cookie, fp, regs->ra);
+	while (fp && !(fp & 0x7))
+		fp = unwind_user_frame(consume_entry, cookie, fp, 0);
+}