linux-kernel - Re: [PATCH v2 1/3] mm, printk: introduce new format string for flags

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87si3ay9u9.fsf@rasmusvillemoes.dk>
Date:	Thu, 10 Dec 2015 09:41:18 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...e.cz>
Subject: Re: [PATCH v2 1/3] mm, printk: introduce new format string for flags

On Thu, Dec 10 2015, Steven Rostedt <rostedt@...dmis.org> wrote:

> On Thu, Dec 10, 2015 at 11:59:44AM +0900, Joonsoo Kim wrote:
>> 
>>   [page_ref:page_ref_unfreeze] bad op token &
>>   [page_ref:page_ref_set] bad op token &
>>   [page_ref:page_ref_mod_unless] bad op token &
>>   [page_ref:page_ref_mod_and_test] bad op token &
>>   [page_ref:page_ref_mod_and_return] bad op token &
>>   [page_ref:page_ref_mod] bad op token &
>>   [page_ref:page_ref_freeze] bad op token &
>> 
>> Following is the format I used.
>> 
>> TP_printk("pfn=0x%lx flags=%pgp count=%d mapcount=%d mapping=%p mt=%d val=%d ret=%d",
>>                 __entry->pfn, &__entry->flags, __entry->count,
>>                 __entry->mapcount, __entry->mapping, __entry->mt,
>>                 __entry->val, __entry->ret)
>> 
>> Could it be solved by 'trace-cmd' itself?
>> Or it's better to pass flags by value?
>> Or should I use something like show_gfp_flags()?
>
> Yes this can be solved in perf and trace-cmd via the parse-events.c file. And
> as soon as that happens, whatever method we decide upon becomes a userspace
> ABI. So don't think you can change it later.

So somewhat off-topic, but this reminds me of a question I've been
meaning to ask: What makes it safe to stash the pointer values in
vbin_printf and only dereference them later in bstr_printf? For plain
pointer printing (%p) it's of course not a problem, but quite a few of
the %p extensions do dereference the pointer in one way or another (at
least %p[dD], %p[mM], %p[iI], %ph, %pE, %pC, %pNF, %pU, %pa and probably
soon %pg).

Rasmus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/