[libcamera-devel] [PATCH v2] v4l2: v4l2_compat: Intercept open64, openat64, and mmap64
Niklas Söderlund
niklas.soderlund at ragnatech.se
Wed Jun 17 13:58:57 CEST 2020
Hi Paul,
Thanks for your work.
On 2020-06-17 18:05:18 +0900, Paul Elder wrote:
> Some applications (eg. Firefox, Google Chrome, Skype) use open64,
> openat64, and mmap64 instead of their non-64 versions that we currently
> intercept. Intercept these calls as well. _LARGEFILE64_SOURCE needs to
> be set so that the 64-bit symbols are available and not synonymous to
> the non-64-bit versions on 64-bit systems.
>
> Also, since we set _FILE_OFFSET_BITS to 32 to force the various open and
> mmap symbols that we export to not be the 64-bit versions, our dlsym to
> get the original open and mmap calls will not automatically be converted
> to their 64-bit versions. Since we intercept both 32-bit and 64-bit
> versions of open and mmap, we should be using the 64-bit version to
> service both. Fetch the 64-bit versions of openat and mmap directly.
>
> musl defines the 64-bit symbols as macros that are equivalent to the
> non-64-bit symbols, so we put compile guards that check if the 64-bit
> symbols are defined.
>
> Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
I feel I lack the skill to judge the musl special case, but for the rest
I think it looks good.
Reviewed-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>
>
> ---
> Changes in v2:
> - squash intercept 64-bit calls and use 64-bit calls into
> this one patch
> - use off64_t instead of __off64_t
> - add compile guard to get musl to play nicely with the 64-bit calls
> coexisting with the non-64-bit calls
> ---
> src/v4l2/meson.build | 1 +
> src/v4l2/v4l2_camera_proxy.cpp | 2 +-
> src/v4l2/v4l2_camera_proxy.h | 3 ++-
> src/v4l2/v4l2_compat.cpp | 33 ++++++++++++++++++++++++++++++++
> src/v4l2/v4l2_compat_manager.cpp | 6 +++---
> src/v4l2/v4l2_compat_manager.h | 5 +++--
> 6 files changed, 43 insertions(+), 7 deletions(-)
>
> diff --git a/src/v4l2/meson.build b/src/v4l2/meson.build
> index 0fb941e..f2e4aaf 100644
> --- a/src/v4l2/meson.build
> +++ b/src/v4l2/meson.build
> @@ -15,6 +15,7 @@ v4l2_compat_cpp_args = [
> # file operations, disable transparent large file support.
> '-U_FILE_OFFSET_BITS',
> '-D_FILE_OFFSET_BITS=32',
> + '-D_LARGEFILE64_SOURCE',
> '-fvisibility=hidden',
> ]
>
> diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> index d7f14e6..7425029 100644
> --- a/src/v4l2/v4l2_camera_proxy.cpp
> +++ b/src/v4l2/v4l2_camera_proxy.cpp
> @@ -75,7 +75,7 @@ void V4L2CameraProxy::close()
> }
>
> void *V4L2CameraProxy::mmap(void *addr, size_t length, int prot, int flags,
> - off_t offset)
> + off64_t offset)
> {
> LOG(V4L2Compat, Debug) << "Servicing mmap";
>
> diff --git a/src/v4l2/v4l2_camera_proxy.h b/src/v4l2/v4l2_camera_proxy.h
> index 7c65c88..27d3e50 100644
> --- a/src/v4l2/v4l2_camera_proxy.h
> +++ b/src/v4l2/v4l2_camera_proxy.h
> @@ -11,6 +11,7 @@
> #include <linux/videodev2.h>
> #include <map>
> #include <memory>
> +#include <sys/mman.h>
> #include <sys/types.h>
> #include <vector>
>
> @@ -28,7 +29,7 @@ public:
> int open(bool nonBlocking);
> void dup();
> void close();
> - void *mmap(void *addr, size_t length, int prot, int flags, off_t offset);
> + void *mmap(void *addr, size_t length, int prot, int flags, off64_t offset);
> int munmap(void *addr, size_t length);
>
> int ioctl(unsigned long request, void *arg);
> diff --git a/src/v4l2/v4l2_compat.cpp b/src/v4l2/v4l2_compat.cpp
> index 2a9a176..7d45ffe 100644
> --- a/src/v4l2/v4l2_compat.cpp
> +++ b/src/v4l2/v4l2_compat.cpp
> @@ -38,6 +38,18 @@ LIBCAMERA_PUBLIC int open(const char *path, int oflag, ...)
> oflag, mode);
> }
>
> +#ifndef open64
> +LIBCAMERA_PUBLIC int open64(const char *path, int oflag, ...)
> +{
> + mode_t mode = 0;
> + if (oflag & O_CREAT || oflag & O_TMPFILE)
> + extract_va_arg(mode_t, mode, oflag);
> +
> + return V4L2CompatManager::instance()->openat(AT_FDCWD, path,
> + oflag | O_LARGEFILE, mode);
> +}
> +#endif
> +
> /* _FORTIFY_SOURCE redirects open to __open_2 */
> LIBCAMERA_PUBLIC int __open_2(const char *path, int oflag)
> {
> @@ -53,6 +65,18 @@ LIBCAMERA_PUBLIC int openat(int dirfd, const char *path, int oflag, ...)
> return V4L2CompatManager::instance()->openat(dirfd, path, oflag, mode);
> }
>
> +#ifndef openat64
> +LIBCAMERA_PUBLIC int openat64(int dirfd, const char *path, int oflag, ...)
> +{
> + mode_t mode = 0;
> + if (oflag & O_CREAT || oflag & O_TMPFILE)
> + extract_va_arg(mode_t, mode, oflag);
> +
> + return V4L2CompatManager::instance()->openat(dirfd, path,
> + oflag | O_LARGEFILE, mode);
> +}
> +#endif
> +
> LIBCAMERA_PUBLIC int __openat_2(int dirfd, const char *path, int oflag)
> {
> return openat(dirfd, path, oflag);
> @@ -75,6 +99,15 @@ LIBCAMERA_PUBLIC void *mmap(void *addr, size_t length, int prot, int flags,
> fd, offset);
> }
>
> +#ifndef mmap64
> +LIBCAMERA_PUBLIC void *mmap64(void *addr, size_t length, int prot, int flags,
> + int fd, off64_t offset)
> +{
> + return V4L2CompatManager::instance()->mmap(addr, length, prot, flags,
> + fd, offset);
> +}
> +#endif
> +
> LIBCAMERA_PUBLIC int munmap(void *addr, size_t length)
> {
> return V4L2CompatManager::instance()->munmap(addr, length);
> diff --git a/src/v4l2/v4l2_compat_manager.cpp b/src/v4l2/v4l2_compat_manager.cpp
> index 56533c4..8da3316 100644
> --- a/src/v4l2/v4l2_compat_manager.cpp
> +++ b/src/v4l2/v4l2_compat_manager.cpp
> @@ -39,11 +39,11 @@ void get_symbol(T &func, const char *name)
> V4L2CompatManager::V4L2CompatManager()
> : cm_(nullptr)
> {
> - get_symbol(fops_.openat, "openat");
> + get_symbol(fops_.openat, "openat64");
> get_symbol(fops_.dup, "dup");
> get_symbol(fops_.close, "close");
> get_symbol(fops_.ioctl, "ioctl");
> - get_symbol(fops_.mmap, "mmap");
> + get_symbol(fops_.mmap, "mmap64");
> get_symbol(fops_.munmap, "munmap");
> }
>
> @@ -200,7 +200,7 @@ int V4L2CompatManager::close(int fd)
> }
>
> void *V4L2CompatManager::mmap(void *addr, size_t length, int prot, int flags,
> - int fd, off_t offset)
> + int fd, off64_t offset)
> {
> V4L2CameraProxy *proxy = getProxy(fd);
> if (!proxy)
> diff --git a/src/v4l2/v4l2_compat_manager.h b/src/v4l2/v4l2_compat_manager.h
> index 14338a5..3d4e512 100644
> --- a/src/v4l2/v4l2_compat_manager.h
> +++ b/src/v4l2/v4l2_compat_manager.h
> @@ -11,6 +11,7 @@
> #include <fcntl.h>
> #include <map>
> #include <memory>
> +#include <sys/mman.h>
> #include <sys/types.h>
> #include <vector>
>
> @@ -30,7 +31,7 @@ public:
> using close_func_t = int (*)(int fd);
> using ioctl_func_t = int (*)(int fd, unsigned long request, ...);
> using mmap_func_t = void *(*)(void *addr, size_t length, int prot,
> - int flags, int fd, off_t offset);
> + int flags, int fd, off64_t offset);
> using munmap_func_t = int (*)(void *addr, size_t length);
>
> openat_func_t openat;
> @@ -51,7 +52,7 @@ public:
> int dup(int oldfd);
> int close(int fd);
> void *mmap(void *addr, size_t length, int prot, int flags,
> - int fd, off_t offset);
> + int fd, off64_t offset);
> int munmap(void *addr, size_t length);
> int ioctl(int fd, unsigned long request, void *arg);
>
> --
> 2.27.0
>
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--
Regards,
Niklas Söderlund
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