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Date: Mon, 11 May 2015 10:59:50 +0200 From: Richard Weinberger <richard@....at> To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>, akpm@...ux-foundation.org CC: linux-kernel@...r.kernel.org Subject: Re: vsprintf: Add support for userspace strings Am 11.05.2015 um 02:24 schrieb Masami Hiramatsu: > On 2015/05/11 4:42, Richard Weinberger wrote: >> While debugging issues I often add (trace_)printks to strategic positions. >> Dealing with user provided string is complicated as an extra buffer a >> copy_from_user() is needed. >> This adds a new format string to allow direct printing of such strings. >> >> My initial plan was to use %pU but 'U' is already taken, therefore >> I used the next letter which comes in mind when one thinks of userpace, >> 'L'. >> The %pL format string works exactly like %s. > > BTW, if you need to do this for debug, you can also use ftrace's kprobe-tracer > (and perf probe) which allows you to dump userspace strings :) Sounds promising! But I fail to use it: $ perf probe -vv -L do_sys_open:0-3 -k /boot/vmlinux-4.1.0-rc2-3.g3541e77-vanilla Line range is 0 to 3 Use vmlinux: /boot/vmlinux-4.1.0-rc2-3.g3541e77-vanilla Failed to find path of kernel module. Error: Failed to show lines. Reason: No such file or directory (Code: -2) Any idea what's the issue? Thanks, //richard -- 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/
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