linux-kernel - Re: [PATCH 1/4] Add support for userspace stacktraces in tracing/iter

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Message-ID: <c62985530810120631g3e464503i8958d160e6b1aa3e@mail.gmail.com>
Date:	Sun, 12 Oct 2008 15:31:59 +0200
From:	"Frédéric Weisbecker" <fweisbec@...il.com>
To:	"Török Edwin" <edwintorok@...il.com>
Cc:	mingo@...e.hu, srostedt@...hat.com, a.p.zijlstra@...llo.nl,
	sandmann@...mi.au.dk, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] Add support for userspace stacktraces in tracing/iter_ctrl

2008/10/12 Török Edwin <edwintorok@...il.com>:
> +static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
> +{
> +       int ret;
> +
> +       if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
> +               return 0;
> +
> +       ret = 1;
> +       pagefault_disable();
> +       if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
> +               ret = 0;
> +       pagefault_enable();
> +
> +       return ret;
> +}
> +

Hello Török,

I don't understand why you are using this pagefault disabling and
atomic copy here.
Wouldn't a simple copy_from_user actually take of this? You don't seem
to be in atomic
context.
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