[libcamera-devel] [PATCH 02/11] libcamera: utils: Add a function to retrieve the libcamera source tree

[Kieran Bingham]

Hi Laurent,

On 27/04/2020 04:17, Laurent Pinchart wrote:
> Similarly to libcameraBuildPath(), there's a need to locate resources
> within the source tree when running libcamera without installing it.
> Support this use case with a new utils::libcameraSourcePath() function.

Eeeep.


> The implementation currently leaks the path to the source tree in the
> installed binary. The data is put in a separate section named .zero
> which will need to be zeroed at installation time to fix this.

Indeed.

I guess we can't get any of this from the debug symbols can we? That
won't be reliable.


> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

This is always going to be painful... but I don't think we should block
this branch just because of leaking the source path - but we certainly
want to fix it soon after.

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>


> ---
>  meson.build                   |  2 ++
>  src/libcamera/include/utils.h |  1 +
>  src/libcamera/utils.cpp       | 37 ++++++++++++++++++++++++++++++++---
>  3 files changed, 37 insertions(+), 3 deletions(-)
> 
> diff --git a/meson.build b/meson.build
> index c6e6a934e54e..2058a6a77ceb 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -26,6 +26,8 @@ libcamera_version = libcamera_git_version.split('+')[0]
>  cc = meson.get_compiler('c')
>  config_h = configuration_data()
>  
> +config_h.set('LIBCAMERA_SOURCE_DIR', '"' + meson.current_source_dir() + '"')
> +
>  if cc.has_header_symbol('execinfo.h', 'backtrace')
>      config_h.set('HAVE_BACKTRACE', 1)
>  endif
> diff --git a/src/libcamera/include/utils.h b/src/libcamera/include/utils.h
> index 242eeded9d50..3334ff16613d 100644
> --- a/src/libcamera/include/utils.h
> +++ b/src/libcamera/include/utils.h
> @@ -188,6 +188,7 @@ private:
>  details::StringSplitter split(const std::string &str, const std::string &delim);
>  
>  std::string libcameraBuildPath();
> +std::string libcameraSourcePath();
>  
>  } /* namespace utils */
>  
> diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
> index 97f9b632e45b..056a67e93e0f 100644
> --- a/src/libcamera/utils.cpp
> +++ b/src/libcamera/utils.cpp
> @@ -360,9 +360,10 @@ bool isLibcameraInstalled()
>   *
>   * During development, it is useful to run libcamera binaries directly from the
>   * build directory without installing them. This function helps components that
> - * need to locate resources, such as IPA modules or IPA proxy workers, by
> - * providing them with the path to the root of the build directory. Callers can
> - * then use it to complement or override searches in system-wide directories.
> + * need to locate resources in the build tree, such as IPA modules or IPA proxy
> + * workers, by providing them with the path to the root of the build directory.
> + * Callers can then use it to complement or override searches in system-wide
> + * directories.
>   *
>   * If libcamera has been installed, the build directory path is not available
>   * and this function returns an empty string.
> @@ -385,6 +386,36 @@ std::string libcameraBuildPath()
>  	return dirname(info.dli_fname) + "/../../";
>  }
>  
> +namespace {
> +/* \todo Figure out a way to zero this section at install time */
> +__attribute__((section(".zero")))
> +const char sourceDirectory[] = LIBCAMERA_SOURCE_DIR;

Even if we can zero this out - it won't give us reproducible builds, as
the section size will be dependant upon the size of the
LIBCAMERA_SOURCE_DIR string.

Now I think about it - I can't recall if we hit the same issue on the
buildPath too.

If this 'works for now' we can defer though.

> +} /* namespace */
> +
> +/**
> + * \brief Retrieve the path to the source directory
> + *
> + * During development, it is useful to run libcamera binaries directly from the
> + * build directory without installing them. This function helps components that
> + * need to locate resources in the source tree, such as IPA configuration
> + * files, by providing them with the path to the root of the source directory.
> + * Callers can then use it to complement or override searches in system-wide
> + * directories.
> + *
> + * If libcamera has been installed, the source directory path is not available
> + * and this function returns an empty string.
> + *
> + * \return The path to the source directory if running from a build, or an empty
> + * string otherwise
> + */
> +std::string libcameraSourcePath()
> +{
> +	if (isLibcameraInstalled())
> +		return std::string();
> +
> +	return std::string(sourceDirectory) + "/";
> +}
> +
>  } /* namespace utils */
>  
>  } /* namespace libcamera */
> 

-- 
Regards
--
Kieran