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Subject[PATCH 1/3] x86/unwind: properly zero-pad 32-bit values in unwind_dump()
Date
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" <hpa@zytor.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@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
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