From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZTnRd-0007iA-U3 for barebox@lists.infradead.org; Mon, 24 Aug 2015 08:49:34 +0000 Date: Mon, 24 Aug 2015 10:49:10 +0200 From: Sascha Hauer Message-ID: <20150824084910.GG18700@pengutronix.de> References: <1440084138-3116-1-git-send-email-pmamonov@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1440084138-3116-1-git-send-email-pmamonov@gmail.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH] RFC: include/usb/ch9.h: pad usb_endpoint_descriptor with 1 byte To: Peter Mamonov Cc: barebox@lists.infradead.org On Thu, Aug 20, 2015 at 06:22:18PM +0300, Peter Mamonov wrote: > This patch fixes "Ooops, address error on load or ifetch!", > caused by "usb" command on MIPS architecture. > > To reproduce the problem follow the following steps: > > 1. Build barebox for MIPS target with -O0 optimization flag: > > diff --git a/Makefile b/Makefile > index 5a7fd5f..da9a8be 100644 > --- a/Makefile > +++ b/Makefile > @@ -301,7 +301,7 @@ CPPFLAGS := -D__KERNEL__ -D__BAREBOX__ $(LINUXINCLUDE) -fno-builtin -ffre > > CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \ > -Werror-implicit-function-declaration \ > - -fno-strict-aliasing -fno-common -Os -pipe > + -fno-strict-aliasing -fno-common -O0 -pipe > AFLAGS := -D__ASSEMBLY__ > > LDFLAGS_barebox := -Map barebox.map > > 2. Plug in a usb flash drive. > > 3. Run the "usb" command: > > barebox@QEMU DUNA:/ usb -s > USB: scanning bus for devices... > &(dev->config.interface[0].ep_desc[0].wMaxPacketSize) = a042732a > Bus 001 Device 001: ID 0000:0000 EHCI Host Controller > &(dev->config.interface[0].ep_desc[0].wMaxPacketSize) = a0429f02 > &(dev->config.interface[0].ep_desc[1].wMaxPacketSize) = a0429f0b > > Ooops, address error on load or ifetch! > > $ 0 : 00000000 00000000 a0429f0b a0429de4 > $ 4 : 00000000 0000000a 00000000 000687e0 > $ 8 : 00000000 00000000 00000000 fa000000 > $12 : 00000001 00000004 00000000 00000000 > $16 : 00000000 00000000 00000000 00000000 > $20 : 00000000 00000000 00000000 00000000 > $24 : 00000000 00000000 > $28 : 00000000 a03ffb40 a03ffb40 a082e9f4 > Hi : 00000000 > Lo : 00000000 > epc : a082ea38 > ra : a082e9f4 > Status: b4000002 > Cause : 00008010 > Config: 88d0c083 > > ### ERROR ### Please RESET the board ### > > The source of the error is the following line of code from the usb_parse_config() function: > > le16_to_cpus(&(dev->config.interface[ifno].ep_desc[epno].\ > wMaxPacketSize)); > > Which tries to load half-word from an un-aligned address 0xa0429f0b stored in v0: > > a082ea38: 94420000 lhu v0,0(v0) > > 0xa0429f0b is an address of wMaxPacketSize member of a struct usb_endpoint_descriptor at offset 4: > > struct usb_endpoint_descriptor { > __u8 bLength; > __u8 bDescriptorType; > __u8 bEndpointAddress; > __u8 bmAttributes; > __le16 wMaxPacketSize; > __u8 bInterval; > __u8 bRefresh; > __u8 bSynchAddress; > } __attribute__ ((packed)); > > The instances of the usb_endpoint_descriptor are stored in a "ep_desc" array: > > struct usb_interface { > ... > struct usb_endpoint_descriptor ep_desc[USB_MAXENDPOINTS]; > }; > > Since the size of the usb_endpoint_descriptor is odd (9 bytes), > the second element of the ep_desc array is un-aligned, > as well as it's member wMaxPacketSize: > > Bus 001 Device 001: ID 0000:0000 EHCI Host Controller > &(dev->config.interface[0].ep_desc[0].wMaxPacketSize) = a0429f02 > &(dev->config.interface[0].ep_desc[1].wMaxPacketSize) = a0429f0b > > A possible fix to this problem is to make the size of the usb_endpoint_descriptor even. > --- > include/usb/ch9.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/usb/ch9.h b/include/usb/ch9.h > index ab5d531..5b261e6 100644 > --- a/include/usb/ch9.h > +++ b/include/usb/ch9.h > @@ -379,6 +379,7 @@ struct usb_endpoint_descriptor { > /* use USB_DT_ENDPOINT*_SIZE in bLength, not sizeof. */ > __u8 bRefresh; > __u8 bSynchAddress; > + __u8 fill; > } __attribute__ ((packed)); This doesn't look very nice since we modify a ch9 defined struct just for the sake of using it in an array somewhere else. We can fix it like this, but please add a comment why we need this. Another way to fix this would be to embed struct usb_endpoint_descriptor in another struct and use that one in an array, like this: struct usb_endpoint { struct usb_endpoint_descriptor desc; }; struct usb_configuration { ... struct usb_endpoint ep_desc[USB_MAXENDPOINTS]; }; Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox