Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 30 Jul 2019 11:47:46 +0100
From:   Russell King - ARM Linux admin <linux@armlinux.org.uk>
To:     Luis Araneda <luaraneda@gmail.com>
Cc:     michal.simek@xilinx.com, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] ARM: zynq: Use memcpy_toio instead of memcpy on smp
 bring-up
Message-ID: <20190730104746.GA1330@shell.armlinux.org.uk>
References: <20190730044326.1805-1-luaraneda@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190730044326.1805-1-luaraneda@gmail.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Jul 30, 2019 at 12:43:26AM -0400, Luis Araneda wrote:
> This fixes a kernel panic (read overflow) on memcpy when
> FORTIFY_SOURCE is enabled.
> 
> The computed size of memcpy args are:
> - p_size (dst): 4294967295 = (size_t) -1
> - q_size (src): 1
> - size (len): 8
> 
> Additionally, the memory is marked as __iomem, so one of
> the memcpy_* functions should be used for read/write
> 
> Signed-off-by: Luis Araneda <luaraneda@gmail.com>
> ---
> 
> For anyone trying to reproduce / debug this, it panics
> before the console has any output.
> I used JTAG to find the panic, but I had to comment-out
> the call to "zynq_slcr_cpu_stop" as it stops the JTAG
> interface and the connection is dropped, at least with OpenOCD.
> 
> I run-tested this on a Digilent Zybo Z7 board
> ---
>  arch/arm/mach-zynq/platsmp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-zynq/platsmp.c b/arch/arm/mach-zynq/platsmp.c
> index a7cfe07156f4..407abade7336 100644
> --- a/arch/arm/mach-zynq/platsmp.c
> +++ b/arch/arm/mach-zynq/platsmp.c
> @@ -57,7 +57,7 @@ int zynq_cpun_start(u32 address, int cpu)
>  			* 0x4: Jump by mov instruction
>  			* 0x8: Jumping address
>  			*/
> -			memcpy((__force void *)zero, &zynq_secondary_trampoline,
> +			memcpy_toio(zero, &zynq_secondary_trampoline,
>  							trampoline_size);
>  			writel(address, zero + trampoline_size);

I'm not convinced that this is correct.  It looks like
zynq_secondary_trampoline could be either ARM or Thumb code - there is
no .arm directive before it.  If it's ARM code, then this is fine.  If
Thumb code, then zynq_secondary_trampoline will be offset by one, and
we will miss copying the first byte of code.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up