| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20240918193914.GB6917@vamoiridPC>
Date: Wed, 18 Sep 2024 21:39:14 +0200
From: Vasileios Amoiridis <vassilisamir@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Vasileios Amoiridis <vassilisamir@...il.com>, dan.carpenter@...aro.org,
linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: iio: pressure: bmp280: Use char instead of s32 for data buffer
On Sat, Sep 14, 2024 at 12:36:11PM +0100, Jonathan Cameron wrote:
> On Fri, 23 Aug 2024 19:20:17 +0200
> Vasileios Amoiridis <vassilisamir@...il.com> wrote:
>
> > As it was reported and discussed here [1], storing the sensor data in an
> > endian aware s32 buffer is not optimal. Advertising the timestamp as an
> > addition of 2 s32 variables which is also implied is again not the best
> > practice. For that reason, change the s32 sensor_data buffer to a char
> > buffer with an extra value for the timestamp (as it is common practice).
> >
> > [1]: https://lore.kernel.org/linux-iio/73d13cc0-afb9-4306-b498-5d821728c3ba@stanley.mountain/
> >
> > Signed-off-by: Vasileios Amoiridis <vassilisamir@...il.com>
> Hi.
> Thanks for poking. Looks like I'd accidentally marked this one handled
> without actually doing so :(
>
Hi Jonathan,
No problem at all!!!
> > ---
> > drivers/iio/pressure/bmp280-core.c | 43 +++++++++++++++++-------------
> > drivers/iio/pressure/bmp280.h | 5 +++-
> > 2 files changed, 28 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
> > index 3deaa57bb3f5..71e481c2f30d 100644
> > --- a/drivers/iio/pressure/bmp280-core.c
> > +++ b/drivers/iio/pressure/bmp280-core.c
> > @@ -1035,7 +1035,8 @@ static irqreturn_t bmp280_trigger_handler(int irq, void *p)
> > goto out;
> > }
> >
> > - data->sensor_data[1] = bmp280_compensate_temp(data, adc_temp);
> > + ret = bmp280_compensate_temp(data, adc_temp);
> > + memcpy(&data->buffer.buf[4], &ret, 4);
>
> The 4's in here are magic indexes. Probably use sizeof(s32) in both cases.
> Maybe for the first one make the fact it's after an s32 explicit with
> &data->buffer.buf[1 * sizeof(s32)]
>
> Of carry an offset through the code that you update when you fill in part of
> the buffer. That is probably cleaner.
>
> int offset = 0;
> stuff
> offset += sizeof(s32);
> mempcy(&data->bufer.buf[offset], &ret, 4);
>
> if offset is used for a later entry then add the new element.
>
>
Looks nice. I could also move both memcpy() after the if's so in case
there is an error I save myself from memcpy() once for no reason.
> >
> > /* Pressure calculations */
> > adc_press = FIELD_GET(BMP280_MEAS_TRIM_MASK, get_unaligned_be24(&data->buf[0]));
> > @@ -1045,10 +1046,10 @@ static irqreturn_t bmp280_trigger_handler(int irq, void *p)
> > }
> >
> > t_fine = bmp280_calc_t_fine(data, adc_temp);
> > + ret = bmp280_compensate_press(data, adc_press, t_fine);
> > + memcpy(&data->buffer.buf[0], &ret, 4);
> >
> > - data->sensor_data[0] = bmp280_compensate_press(data, adc_press, t_fine);
> > -
> > - iio_push_to_buffers_with_timestamp(indio_dev, &data->sensor_data,
> > + iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
> > iio_get_time_ns(indio_dev));
> >
> > out:
> > @@ -1148,7 +1149,8 @@ static irqreturn_t bme280_trigger_handler(int irq, void *p)
> > goto out;
> > }
> >
> > - data->sensor_data[1] = bmp280_compensate_temp(data, adc_temp);
> > + ret = bmp280_compensate_temp(data, adc_temp);
> > + memcpy(&data->buffer.buf[4], &ret, 4);
> >
> > /* Pressure calculations */
> > adc_press = FIELD_GET(BMP280_MEAS_TRIM_MASK, get_unaligned_be24(&data->buf[0]));
> > @@ -1158,8 +1160,8 @@ static irqreturn_t bme280_trigger_handler(int irq, void *p)
> > }
> >
> > t_fine = bmp280_calc_t_fine(data, adc_temp);
> > -
> > - data->sensor_data[0] = bmp280_compensate_press(data, adc_press, t_fine);
> > + ret = bmp280_compensate_press(data, adc_press, t_fine);
> > + memcpy(&data->buffer.buf[0], &ret, 4);
> >
> > /* Humidity calculations */
> > adc_humidity = get_unaligned_be16(&data->buf[6]);
> > @@ -1168,9 +1170,11 @@ static irqreturn_t bme280_trigger_handler(int irq, void *p)
> > dev_err(data->dev, "reading humidity skipped\n");
> > goto out;
> > }
> > - data->sensor_data[2] = bme280_compensate_humidity(data, adc_humidity, t_fine);
> >
> > - iio_push_to_buffers_with_timestamp(indio_dev, &data->sensor_data,
> > + ret = bme280_compensate_humidity(data, adc_humidity, t_fine);
> > + memcpy(&data->buffer.buf[8], &ret, 4);
> as above, but here it is I guess after 2 other elements, so
>
> 2 * sizeof(s32)
>
> > +
> > + iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
> > iio_get_time_ns(indio_dev));
> >
> > out:
> > @@ -1628,7 +1632,8 @@ static irqreturn_t bmp380_trigger_handler(int irq, void *p)
> > goto out;
> > }
> >
> > - data->sensor_data[1] = bmp380_compensate_temp(data, adc_temp);
> > + ret = bmp380_compensate_temp(data, adc_temp);
> > + memcpy(&data->buffer.buf[4], &ret, 4);
> >
> > /* Pressure calculations */
> > adc_press = get_unaligned_le24(&data->buf[0]);
> > @@ -1638,10 +1643,10 @@ static irqreturn_t bmp380_trigger_handler(int irq, void *p)
> > }
> >
> > t_fine = bmp380_calc_t_fine(data, adc_temp);
> > + ret = bmp380_compensate_press(data, adc_press, t_fine);
> > + memcpy(&data->buffer.buf[0], &ret, 4);
> >
> > - data->sensor_data[0] = bmp380_compensate_press(data, adc_press, t_fine);
> > -
> > - iio_push_to_buffers_with_timestamp(indio_dev, &data->sensor_data,
> > + iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
> > iio_get_time_ns(indio_dev));
> >
> > out:
> > @@ -2203,12 +2208,12 @@ static irqreturn_t bmp580_trigger_handler(int irq, void *p)
> > }
> >
> > /* Temperature calculations */
> > - memcpy(&data->sensor_data[1], &data->buf[0], 3);
> > + memcpy(&data->buffer.buf[4], &data->buf[0], 3);
> >
> > /* Pressure calculations */
> > - memcpy(&data->sensor_data[0], &data->buf[3], 3);
> > + memcpy(&data->buffer.buf[0], &data->buf[3], 3);
>
> > - iio_push_to_buffers_with_timestamp(indio_dev, &data->sensor_data,
> > + iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
> > iio_get_time_ns(indio_dev));
> >
> > out:
> > @@ -2522,15 +2527,15 @@ static irqreturn_t bmp180_trigger_handler(int irq, void *p)
> > if (ret)
> > goto out;
> >
> > - data->sensor_data[1] = chan_value;
> > + memcpy(&data->buffer.buf[4], &chan_value, 4);
> >
> > ret = bmp180_read_press(data, &chan_value);
> > if (ret)
> > goto out;
> >
> > - data->sensor_data[0] = chan_value;
> > + memcpy(&data->buffer.buf[0], &chan_value, 4);
> >
> > - iio_push_to_buffers_with_timestamp(indio_dev, &data->sensor_data,
> > + iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
> > iio_get_time_ns(indio_dev));
> >
> > out:
> > diff --git a/drivers/iio/pressure/bmp280.h b/drivers/iio/pressure/bmp280.h
> > index ccacc67c1473..a853b6d5bdfa 100644
> > --- a/drivers/iio/pressure/bmp280.h
> > +++ b/drivers/iio/pressure/bmp280.h
> > @@ -411,7 +411,10 @@ struct bmp280_data {
> > * Data to push to userspace triggered buffer. Up to 3 channels and
> > * s64 timestamp, aligned.
> > */
> > - s32 sensor_data[6] __aligned(8);
> > + struct {
> > + u8 buf[12];
> > + s64 ts __aligned(8);
>
> We have a new aligned_s64 that is cleaner for these cases. It's only
> in my togreg branch currently though so you'll need to base on that
> to use it.
>
> Jonathan
>
>
Looks nice, I will try it.
Cheers,
Vasilis
> > + } buffer;
> >
> > /*
> > * DMA (thus cache coherency maintenance) may require the
>
Powered by blists - more mailing lists