lkml.org 
[lkml]   [2017]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] mtd: spi-nor: stm32-quadspi: avoid unintialized return code
From
Date


On 09/14/2017 05:24 PM, Geert Uytterhoeven wrote:
> Hi Ludovic,
>
> On Thu, Sep 14, 2017 at 5:13 PM, Ludovic BARRE <ludovic.barre@st.com> wrote:
>> On 09/14/2017 03:38 PM, Geert Uytterhoeven wrote:
>>> On Thu, Sep 14, 2017 at 1:06 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>>> If we send zero-length data to stm32_qspi_tx_poll() on older
>>>> compiler versions such as gcc-4.6, we get warned that the
>>>> return code is uninitialized:
>>>>
>>>> drivers/mtd/spi-nor/stm32-quadspi.c:248:2: error: ‘ret’ may be used
>>>> uninitialized in this function [-Werror=uninitialized]
>>>>
>>>> On newer compiler versions, the return code is always zero
>>>> in this case, as the local variable gets optimized away and
>>>> is assumed to be zero after the loop completes without error.
>>>>
>>>> This changes the function to instead return -EINVAL if it
>>>> ever gets called with a zero length buffer.
>>>>
>>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82203
>>>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>>>> ---
>>>> drivers/mtd/spi-nor/stm32-quadspi.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/mtd/spi-nor/stm32-quadspi.c
>>>> b/drivers/mtd/spi-nor/stm32-quadspi.c
>>>> index 86c0931543c5..711cfe7aa4bf 100644
>>>> --- a/drivers/mtd/spi-nor/stm32-quadspi.c
>>>> +++ b/drivers/mtd/spi-nor/stm32-quadspi.c
>>>> @@ -227,7 +227,7 @@ static int stm32_qspi_tx_poll(struct stm32_qspi
>>>> *qspi,
>>>> void (*tx_fifo)(u8 *, void __iomem *);
>>>> u32 len = cmd->len, sr;
>>>> u8 *buf = cmd->buf;
>>>> - int ret;
>>>> + int ret = -EINVAL;
>>>>
>>>> if (cmd->qspimode == CCR_FMODE_INDW)
>>>> tx_fifo = stm32_qspi_write_fifo;
>>>
>>>
>>> See also "[PATCH] mtd: spi-nor: stm32-quadspi: Fix uninitialized error
>>> return code"
>>> (https://patchwork.kernel.org/patch/9842173/)
>>
>> hi Arnd, Geert
>>
>> sorry, I was forgot this thread while my holidays
>>
>> Geert: what do you mean like "similar bugs in the future" in "If you
>> initialized ret at the beginning, you lose the ability to catch newly
>> introduced similar bugs in the future."
>
> If you pre-initialize ret at the top, you loose the ability of the compiler
> to detect at compile-time if ret is never written to later. It will just return
> -EINVAL at runtime.
>
> With my version, if the code is modified later and another "return ret" is
> added, the compiler will detect if there's a code path that forgets
> to assign a value to ret.
Ok, it's clear for me.
I favor geert's solution.
Arnd what do you think ?

>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
>

\
 
 \ /
  Last update: 2017-09-14 19:29    [W:0.065 / U:0.868 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site