1 files changed, 36 insertions, 2 deletions

diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index d145a0b1f529..3dc26f95d46e 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -44,7 +44,8 @@ static void unwind_dump(struct unwind_state *state)
                         state->stack_info.type, state->stack_info.next_sp,
                         state->stack_mask, state->graph_idx);
 
-        for (sp = state->orig_sp; sp; sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
+        for (sp = PTR_ALIGN(state->orig_sp, sizeof(long)); sp;
+             sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
                 if (get_stack_info(sp, state->task, &stack_info, &visit_mask))
                         break;
 
@@ -174,6 +175,7 @@ static bool is_last_task_frame(struct unwind_state *state)
  * This determines if the frame pointer actually contains an encoded pointer to
  * pt_regs on the stack.  See ENCODE_FRAME_POINTER.
  */
+#ifdef CONFIG_X86_64
 static struct pt_regs *decode_frame_pointer(unsigned long *bp)
 {
         unsigned long regs = (unsigned long)bp;
@@ -183,6 +185,23 @@ static struct pt_regs *decode_frame_pointer(unsigned long *bp)
 
         return (struct pt_regs *)(regs & ~0x1);
 }
+#else
+static struct pt_regs *decode_frame_pointer(unsigned long *bp)
+{
+        unsigned long regs = (unsigned long)bp;
+
+        if (regs & 0x80000000)
+                return NULL;
+
+        return (struct pt_regs *)(regs | 0x80000000);
+}
+#endif
+
+#ifdef CONFIG_X86_32
+#define KERNEL_REGS_SIZE (sizeof(struct pt_regs) - 2*sizeof(long))
+#else
+#define KERNEL_REGS_SIZE (sizeof(struct pt_regs))
+#endif
 
 static bool update_stack_state(struct unwind_state *state,
                                unsigned long *next_bp)
@@ -202,7 +221,7 @@ static bool update_stack_state(struct unwind_state *state,
         regs = decode_frame_pointer(next_bp);
         if (regs) {
                 frame = (unsigned long *)regs;
-                len = regs_size(regs);
+                len = KERNEL_REGS_SIZE;
                 state->got_irq = true;
         } else {
                 frame = next_bp;
@@ -226,6 +245,14 @@ static bool update_stack_state(struct unwind_state *state,
             frame < prev_frame_end)
                 return false;
 
+        /*
+         * On 32-bit with user mode regs, make sure the last two regs are safe
+         * to access:
+         */
+        if (IS_ENABLED(CONFIG_X86_32) && regs && user_mode(regs) &&
+            !on_stack(info, frame, len + 2*sizeof(long)))
+                return false;
+
         /* Move state to the next frame: */
         if (regs) {
                 state->regs = regs;
@@ -328,6 +355,13 @@ bad_address:
             state->regs->sp < (unsigned long)task_pt_regs(state->task))
                 goto the_end;
 
+        /*
+         * There are some known frame pointer issues on 32-bit.  Disable
+         * unwinder warnings on 32-bit until it gets objtool support.
+         */
+        if (IS_ENABLED(CONFIG_X86_32))
+                goto the_end;
+
         if (state->regs) {
                 printk_deferred_once(KERN_WARNING
                         "WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",