[PATCH 1/3] x86/unwind: properly zero-pad 32-bit values in unwind_dump()

[Josh Poimboeuf]

On x86-32, 32-bit stack values printed by unwind_dump() are confusingly
zero-padded to 16 characters (64 bits):

  unwind stack type:0 next_sp:  (null) mask:a graph_idx:0
  f50cdebc: 00000000f50cdec4 (0xf50cdec4)
  f50cdec0: 00000000c40489b7 (irq_exit+0x87/0xa0)
  ...

Instead, base the field width on the size of a long integer so that it
looks right on both x86-32 and x86-64.

x86-32:

  unwind stack type:1 next_sp:  (null) mask:0x2 graph_idx:0
  c0ee9d98: c0ee9de0 (init_thread_union+0x1de0/0x2000)
  c0ee9d9c: c043fd90 (__save_stack_trace+0x50/0xe0)
  ...

x86-64:

  unwind stack type:1 next_sp:          (null) mask:0x2 graph_idx:0
  ffffffff81e03b88: ffffffff81e03c10 (init_thread_union+0x3c10/0x4000)
  ffffffff81e03b90: ffffffff81048f8e (__save_stack_trace+0x5e/0x100)
  ...

Reported-by: "H. Peter Anvin" <h...@zytor.com>
Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
---
 arch/x86/kernel/unwind_frame.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index c461135..3ebe687 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -48,11 +48,13 @@ static void unwind_dump(struct unwind_state *state, 
unsigned long *sp)
 
                if (zero) {
                        if (!prev_zero)
-                               printk_deferred("%p: %016x ...\n", sp, 0);
+                               printk_deferred("%p: %0*x ...\n",
+                                               sp, BITS_PER_LONG/4, 0);
                        continue;
                }
 
-               printk_deferred("%p: %016lx (%pB)\n", sp, word, (void *)word);
+               printk_deferred("%p: %0*lx (%pB)\n",
+                               sp, BITS_PER_LONG/4, word, (void *)word);
        }
 }
 
-- 
2.7.4