Re: [PATCH 4/4] x86/jump-label: Show where and what was wrong on errors

Borislav Petkov
2013-08-07T17:20:53Z

On Wed, Aug 07, 2013 at 12:49:38PM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <srostedt@redhat.com>
>
> When modifying text sections for jump labels, a paranoid check is
> performed. If the check fails, the system "bugs". But why it failed
> is not shown.
>
> The BUG_ON()s in the jump label update code is replaced with bug_at(ip).
> This is a function that will show what pointer failed, and what was
> at the location of the failure that made jump label panic.
>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
> arch/x86/kernel/jump_label.c | 21 ++++++++++++++++++---
> 1 file changed, 18 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
> index 24cf2b2..912a528 100644
> --- a/arch/x86/kernel/jump_label.c
> +++ b/arch/x86/kernel/jump_label.c
> @@ -24,6 +24,18 @@ union jump_code_union {
> } __attribute__((packed));
> };
>
> +static void bug_at(unsigned char *ip, int line)
> +{
> + /*
> + * The location is not an op that we were expecting.
> + * Something went wrong. Crash the box, as something could be
> + * corrupting the kernel.
> + */
> + pr_warning("Unexpected op at %pS [%p] (%02x %02x %02x %02x %02x) %s:%d\n",
> + ip, ip, ip[0], ip[1], ip[2], ip[3], ip[4], __FILE__, line);
> + BUG();

Why not simply

panic("Unexpected...")

?

Besides, BUG can be disabled in CONFIG_EXPERT.

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
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