[libcamera-devel] [PATCH v3 1/6] libcamera: v4l2_device, v4l2_videodevice: call open system call directly

[Laurent Pinchart]

Hi Paul,

Thank you for the patch.

On Mon, Dec 23, 2019 at 01:26:15AM -0600, Paul Elder wrote:
> We are preparing to integrate the V4L2 adaptation layer, which will
> intercept open() calls (among others) via LD_PRELOAD. To prevent
> libcamera's own open() calls from being intercepted, replace them with a
> direct syscall.
> 
> Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> ---
> Changes in v3:
> - change SYS_open to SYS_openat
> 
> No change in v2
> ---
>  src/libcamera/v4l2_device.cpp      | 3 ++-
>  src/libcamera/v4l2_videodevice.cpp | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> index 0452f801..c13eddc8 100644
> --- a/src/libcamera/v4l2_device.cpp
> +++ b/src/libcamera/v4l2_device.cpp
> @@ -11,6 +11,7 @@
>  #include <iomanip>
>  #include <string.h>
>  #include <sys/ioctl.h>
> +#include <sys/syscall.h>
>  #include <unistd.h>
>  
>  #include "log.h"
> @@ -75,7 +76,7 @@ int V4L2Device::open(unsigned int flags)
>  		return -EBUSY;
>  	}
>  
> -	int ret = ::open(deviceNode_.c_str(), flags);
> +	int ret = syscall(SYS_openat, AT_FDCWD, deviceNode_.c_str(), flags);
>  	if (ret < 0) {
>  		ret = -errno;
>  		LOG(V4L2, Error) << "Failed to open V4L2 device: "
> diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> index 13e02323..50e3bc11 100644
> --- a/src/libcamera/v4l2_videodevice.cpp
> +++ b/src/libcamera/v4l2_videodevice.cpp
> @@ -13,6 +13,7 @@
>  #include <string.h>
>  #include <sys/ioctl.h>
>  #include <sys/mman.h>
> +#include <sys/syscall.h>
>  #include <sys/time.h>
>  #include <unistd.h>
>  #include <vector>
> @@ -1426,7 +1427,7 @@ int V4L2M2MDevice::open()
>  	 * as the V4L2VideoDevice::open() retains a handle by duplicating the
>  	 * fd passed in.
>  	 */
> -	fd = ::open(deviceNode_.c_str(), O_RDWR | O_NONBLOCK);
> +	fd = syscall(SYS_openat, AT_FDCWD, deviceNode_.c_str(), O_RDWR | O_NONBLOCK);

Nitpicking, you can wrap this line.

>  	if (fd < 0) {
>  		ret = -errno;
>  		LOG(V4L2, Error)

-- 
Regards,

Laurent Pinchart