[libcamera-devel] [PATCH v5 1/4] libcamera: v4l2_device, v4l2_videodevice: call open system call directly

[Paul Elder]

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>

---
No change in v5

Changes in v4:
- one cosmetic change

Changes in v3:
- change SYS_open to SYS_openat

No change in v2
---
 src/libcamera/v4l2_device.cpp      | 3 ++-
 src/libcamera/v4l2_videodevice.cpp | 4 +++-
 2 files changed, 5 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..033f7cc0 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 +1427,8 @@ 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);
 	if (fd < 0) {
 		ret = -errno;
 		LOG(V4L2, Error)
-- 
2.24.1