3 files changed, 34 insertions, 13 deletions

diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index c1688c2d0a12..1f86e1b0a5cd 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -56,18 +56,27 @@ void unwind_start(struct unwind_state *state, struct task_struct *task,
 
 #if defined(CONFIG_UNWINDER_ORC) || defined(CONFIG_UNWINDER_FRAME_POINTER)
 /*
- * WARNING: The entire pt_regs may not be safe to dereference.  In some cases,
- * only the iret frame registers are accessible.  Use with caution!
+ * If 'partial' returns true, only the iret frame registers are valid.
  */
-static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
+static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state,
+                                                    bool *partial)
 {
         if (unwind_done(state))
                 return NULL;
 
+        if (partial) {
+#ifdef CONFIG_UNWINDER_ORC
+                *partial = !state->full_regs;
+#else
+                *partial = false;
+#endif
+        }
+
         return state->regs;
 }
 #else
-static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
+static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state,
+                                                    bool *partial)
 {
         return NULL;
 }
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 5fa110699ed2..d0bb176a7261 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -76,12 +76,23 @@ void show_iret_regs(struct pt_regs *regs)
                 regs->sp, regs->flags);
 }
 
-static void show_regs_safe(struct stack_info *info, struct pt_regs *regs)
+static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
+                                  bool partial)
 {
-        if (on_stack(info, regs, sizeof(*regs)))
+        /*
+         * These on_stack() checks aren't strictly necessary: the unwind code
+         * has already validated the 'regs' pointer.  The checks are done for
+         * ordering reasons: if the registers are on the next stack, we don't
+         * want to print them out yet.  Otherwise they'll be shown as part of
+         * the wrong stack.  Later, when show_trace_log_lvl() switches to the
+         * next stack, this function will be called again with the same regs so
+         * they can be printed in the right context.
+         */
+        if (!partial && on_stack(info, regs, sizeof(*regs))) {
                 __show_regs(regs, 0);
-        else if (on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
-                          IRET_FRAME_SIZE)) {
+
+        } else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
+                                       IRET_FRAME_SIZE)) {
                 /*
                  * When an interrupt or exception occurs in entry code, the
                  * full pt_regs might not have been saved yet.  In that case
@@ -98,6 +109,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
         struct stack_info stack_info = {0};
         unsigned long visit_mask = 0;
         int graph_idx = 0;
+        bool partial;
 
         printk("%sCall Trace:\n", log_lvl);
 
@@ -140,7 +152,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
                         printk("%s <%s>\n", log_lvl, stack_name);
 
                 if (regs)
-                        show_regs_safe(&stack_info, regs);
+                        show_regs_if_on_stack(&stack_info, regs, partial);
 
                 /*
                  * Scan the stack, printing any text addresses we find.  At the
@@ -164,7 +176,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
 
                         /*
                          * Don't print regs->ip again if it was already printed
-                         * by show_regs_safe() below.
+                         * by show_regs_if_on_stack().
                          */
                         if (regs && stack == &regs->ip)
                                 goto next;
@@ -199,9 +211,9 @@ next:
                         unwind_next_frame(&state);
 
                         /* if the frame has entry regs, print them */
-                        regs = unwind_get_entry_regs(&state);
+                        regs = unwind_get_entry_regs(&state, &partial);
                         if (regs)
-                                show_regs_safe(&stack_info, regs);
+                                show_regs_if_on_stack(&stack_info, regs, partial);
                 }
 
                 if (stack_name)
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 8dabd7bf1673..60244bfaf88f 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -98,7 +98,7 @@ static int __save_stack_trace_reliable(struct stack_trace *trace,
         for (unwind_start(&state, task, NULL, NULL); !unwind_done(&state);
              unwind_next_frame(&state)) {
 
-                regs = unwind_get_entry_regs(&state);
+                regs = unwind_get_entry_regs(&state, NULL);
                 if (regs) {
                         /*
                          * Kernel mode registers on the stack indicate an