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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id z131sm355644pfc.159.2021.08.18.10.15.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Aug 2021 10:15:53 -0700 (PDT) Date: Wed, 18 Aug 2021 10:15:52 -0700 From: Kees Cook To: Alan Stern Cc: Greg Kroah-Hartman , Al Cooper , linux-usb@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com, Arnd Bergmann , Florian Fainelli , Andy Shevchenko , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH 2/2] USB: EHCI: Add alias for Broadcom INSNREG Message-ID: <202108181013.63E7B4903B@keescook> References: <20210818043035.1308062-1-keescook@chromium.org> <20210818043035.1308062-3-keescook@chromium.org> <20210818145736.GD193695@rowland.harvard.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210818145736.GD193695@rowland.harvard.edu> Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Wed, Aug 18, 2021 at 10:57:36AM -0400, Alan Stern wrote: > On Tue, Aug 17, 2021 at 09:30:34PM -0700, Kees Cook wrote: > > Refactor struct ehci_regs to avoid accessing beyond the end of > > port_status. This change results in no difference in the resulting > > object code. > > > > Avoids several warnings when building with -Warray-bounds: > > > > drivers/usb/host/ehci-brcm.c: In function 'ehci_brcm_reset': > > drivers/usb/host/ehci-brcm.c:113:32: warning: array subscript 16 is above array bounds of 'u32[15]' {aka 'unsigned int[15]'} [-Warray-bounds] > > 113 | ehci_writel(ehci, 0x00800040, &ehci->regs->port_status[0x10]); > > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > In file included from drivers/usb/host/ehci.h:274, > > from drivers/usb/host/ehci-brcm.c:15: > > ./include/linux/usb/ehci_def.h:132:7: note: while referencing 'port_status' > > 132 | u32 port_status[HCS_N_PORTS_MAX]; > > | ^~~~~~~~~~~ > > > > Note that the documentation around this proprietary register is > > confusing. If "USB_EHCI_INSNREG00" is at port_status[0x0f], its offset > > would be 0x80 (not 0x90). The code uses port_status[0x10], so is that > > not using "USB_EHCI_INSNREG00"? > > I suspect the 0x90 value in the comment is a typo for 0x80. That'd be my conclusion too. I've updated this for v2. > > > Perhaps port_status[0x10] is USB_EHCI_INSNREG01 and port_status[0x12] > > is USB_EHCI_INSNREG03? If so, the union could be adjusted to better > > represent the layout. > > > > Cc: Greg Kroah-Hartman > > Cc: Al Cooper > > Cc: Alan Stern > > Cc: linux-usb@vger.kernel.org > > Cc: bcm-kernel-feedback-list@broadcom.com > > Suggested-by: Arnd Bergmann > > Fixes: 9df231511bd6 ("usb: ehci: Add new EHCI driver for Broadcom STB SoC's") > > Signed-off-by: Kees Cook > > --- > > drivers/usb/host/ehci-brcm.c | 11 +++++------ > > include/linux/usb/ehci_def.h | 16 ++++++++++++++-- > > 2 files changed, 19 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/usb/host/ehci-brcm.c b/drivers/usb/host/ehci-brcm.c > > index 3e0ebe8cc649..5d232d3701f9 100644 > > --- a/drivers/usb/host/ehci-brcm.c > > +++ b/drivers/usb/host/ehci-brcm.c > > @@ -110,8 +110,8 @@ static int ehci_brcm_reset(struct usb_hcd *hcd) > > * bus usage > > * port_status[0x0f] = Broadcom-proprietary USB_EHCI_INSNREG00 @ 0x90 > > This last comment line is no longer necessary, thanks to the revised > port definitions. And since it is actively misleading, with the 0x90 > instead of 0x80, I think it should be removed entirely. Done. > > > */ > > - ehci_writel(ehci, 0x00800040, &ehci->regs->port_status[0x10]); > > - ehci_writel(ehci, 0x00000001, &ehci->regs->port_status[0x12]); > > + ehci_writel(ehci, 0x00800040, &ehci->regs->brcm_insnreg[0]); > > + ehci_writel(ehci, 0x00000001, &ehci->regs->brcm_insnreg[2]); > > > > return ehci_setup(hcd); > > } > > @@ -223,11 +223,10 @@ static int __maybe_unused ehci_brcm_resume(struct device *dev) > > /* > > * SWLINUX-1705: Avoid OUT packet underflows during high memory > > * bus usage > > - * port_status[0x0f] = Broadcom-proprietary USB_EHCI_INSNREG00 > > - * @ 0x90 > > + * port_status[0x0f] = Broadcom-proprietary USB_EHCI_INSNREG00 @ 0x90 > > Same here. > > > */ > > - ehci_writel(ehci, 0x00800040, &ehci->regs->port_status[0x10]); > > - ehci_writel(ehci, 0x00000001, &ehci->regs->port_status[0x12]); > > + ehci_writel(ehci, 0x00800040, &ehci->regs->brcm_insnreg[0]); > > + ehci_writel(ehci, 0x00000001, &ehci->regs->brcm_insnreg[2]); > > > > ehci_resume(hcd, false); > > > > diff --git a/include/linux/usb/ehci_def.h b/include/linux/usb/ehci_def.h > > index 5398f571113b..86f0909cab99 100644 > > --- a/include/linux/usb/ehci_def.h > > +++ b/include/linux/usb/ehci_def.h > > @@ -182,11 +182,23 @@ struct ehci_regs { > > * its EHCI controller has both TT and LPM support. HOSTPCx are extensions to > > * PORTSCx > > */ > > - /* HOSTPC: offset 0x84 */ > > - u32 hostpc[HCS_N_PORTS_MAX]; > > + union { > > + /* HOSTPC: offset 0x84 */ > > + u32 hostpc[HCS_N_PORTS_MAX]; > > #define HOSTPC_PHCD (1<<22) /* Phy clock disable */ > > #define HOSTPC_PSPD (3<<25) /* Port speed detection */ > > > > + /* > > + * This was originally documented as: > > + * "port_status[0x0f] = Broadcom-proprietary USB_EHCI_INSNREG00 @ 0x90" > > + * but this doesn't make sense: the code was using > > + * port_status[0x10]. port_status[0x0f] would be reserved4. > > + * Also, none of these are near 0x90. port_status[0x10] is > > + * offset 0x84, and port_status[0x0f] would be 0x80. > > + */ > > This comment is entirely inappropriate. It's the sort of thing that > belongs in the git history, not in the code. I wanted it to be easily discoverable, but since we've got a preferred result now, I'm dropping this and orienting against 0x80. > > > + u32 brcm_insnreg[3]; > > Given the notation in the original comments, perhaps it would be better > to define this as: > > struct { /* Broadcom proprietary registers */ > u32 brcm_insnreg01; /* offset 0x84 */ > u32 brcm_insnreg02; > u32 brcm_insnreg03; > }; Following the other register arrays, I'm going to keep an array for this, but adjust the numbering to start at 0 @ 0x80 so the code will poke offset 1 and 3. > I don't know. It would be nice to hear from somebody at Broadcom. Agreed. :) Thanks for the review! -- Kees Cook