linux-kernel - Re: [PATCH V4] mm: fix kernel crash in khugepaged thread

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: <8582F660-B54A-474B-960E-CD5D0FF6428F@gmail.com>
Date:	Tue, 17 Nov 2015 11:58:44 +0800
From:	yalin wang <yalin.wang2010@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Vlastimil Babka <vbabka@...e.cz>, Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ebru Akagunduz <ebru.akagunduz@...il.com>,
	Rik van Riel <riel@...hat.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	jmarchan@...hat.com, mgorman@...hsingularity.net,
	willy@...ux.intel.com, linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org
Subject: Re: [PATCH V4] mm: fix kernel crash in khugepaged thread


> On Nov 17, 2015, at 10:43, Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> On Tue, 17 Nov 2015 10:21:47 +0800
> yalin wang <yalin.wang2010@...il.com> wrote:
> 
> 
>> i have not tried ,
>> just a question,
>> if you print a %s , but don’t call trace_define_field() do define this string in
>> __entry ,  how does user space perf tool to get this string info and print it ?
>> i am curious ..
>> i can try this when i have time.  and report to you .
> 
> Because the print_fmt has nothing to do with the fields. You can have
> as your print_fmt as:
> 
> 	TP_printk("Message = %s", "hello dolly!")
> 
> And both userspace and the kernel with process that correctly (if I got
> string processing working in userspace, which I believe I do). The
> string is processed, it's not dependent on TP_STRUCT__entry() unless it
> references a field there. Which can also be used too:
> 
> 	TP_printk("Message = %s", __entry->musical ? "Hello dolly!" :
> 			"Death Trap!")
> 
> userspace will see in the entry:
> 
> print_fmt: "Message = %s", REC->musical ? "Hello dolly!" : "Death Trap!"
> 
> as long as the field "musical" exists, all is well.
> 
> -- Steve
Aha,  i see.
Thanks very much for your explanation.
Better print fat is :   
TP_printk("mm=%p, scan_pfn=%s, writable=%d, referenced=%d, none_or_zero=%d, status=%s, unmapped=%d",
               __entry->mm,
		__entry->pfn == (-1UL) ? "(null)" :  itoa(buff,  __entry->pin, 10), …..)

is this possible ?

Thanks








--
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/