From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Jones Subject: Re: [RESEND v4 2/6] remoteproc: debugfs: Add ability to boot remote processor using debugfs Date: Thu, 3 Dec 2015 17:28:30 +0000 Message-ID: <20151203172830.GB26902@x1> References: <1448370862-19120-1-git-send-email-lee.jones@linaro.org> <5329827.I5W30K072M@wuerfel> <20151203130341.GA26902@x1> <2600153.9u9Z7N2IT1@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <2600153.9u9Z7N2IT1@wuerfel> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Arnd Bergmann Cc: Ohad Ben-Cohen , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Florian Fainelli , kernel-F5mvAk5X5gdBDgjK7y7TUQ@public.gmane.org, Nathan_Lynch-nmGgyN9QBj3QT0dZR+AlfA@public.gmane.org, "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , ludovic.barre-qxv4g6HH51o@public.gmane.org, Bjorn Andersson , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Maxime Coquelin List-Id: devicetree@vger.kernel.org On Thu, 03 Dec 2015, Arnd Bergmann wrote: > On Thursday 03 December 2015 13:03:41 Lee Jones wrote: > > On Thu, 03 Dec 2015, Arnd Bergmann wrote: > >=20 > > > On Thursday 03 December 2015 12:26:34 Lee Jones wrote: > > > > > > > > > > > > +static ssize_t rproc_state_write(struct file *filp, const = char __user *userbuf, > > > > > > + size_t count, loff_t *ppos= ) > > > > > > +{ > > > > > > + struct rproc *rproc =3D filp->private_data; > > > > > > + char buf[10]; > > > > > > + int ret; > > > > > > + > > > > > > + if (count > sizeof(buf)) > > > > > > + return count; > > > > > > + ret =3D copy_from_user(buf, userbuf, count); > > > > > > + if (ret) > > > > > > + return -EFAULT; > > > > > > + > > > > > > + if (buf[count - 1] =3D=3D '\n') > > > > > > + buf[count - 1] =3D '\0'; > > > > >=20 > > > > > I believe you can get here with count =3D 0. > > > >=20 > > > > I'm pretty sure you can't. > > > >=20 > > > > If you are sure that you can, if you can provide me with a way = of > > > > testing, I'd be happy to put in provisions. > > > >=20 > > >=20 > > > I think that a zero-length write() from user space ends up in the= write > > > file operation. > >=20 > > I tested this and didn't see it enter write(). My conclusion was t= hat > > if the file doesn't change, then nothing is triggered. > >=20 >=20 > Ah, interesting. I haven't tried myself, and just tried to read the > code. Maybe glibc already catches zero-length writes before it gets > into the kernel, or I just missed the part of the syscall that checks > for this. Glibc is responsible indeed: =20 http://osxr.org/glibc/source/io/write.c --=20 Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org =E2=94=82 Open source software for ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html