[libcamera-devel] [PATCH LIBCAMERA 3/4] libcamera: ipa_proxy: search for proxy in build tree

[Kaaira Gupta]

When libcamera is build and tested before installing, it will
be unable to locate the path to proxy files,or previously
installed files in the system path may be incorrect to load.

Hence, when libcamera is not installed and running from a build
tree, identify the location of that tree by finding the path of
active libcamera.so, and from that point add the relative path to
the proxy file.

Signed-off-by: Kaaira Gupta <kgupta at es.iitr.ac.in>
---
 src/libcamera/ipa_proxy.cpp | 54 +++++++++++++++++++++++++++++++++----
 1 file changed, 49 insertions(+), 5 deletions(-)

diff --git a/src/libcamera/ipa_proxy.cpp b/src/libcamera/ipa_proxy.cpp
index 363d034..d7c32a1 100644
--- a/src/libcamera/ipa_proxy.cpp
+++ b/src/libcamera/ipa_proxy.cpp
@@ -9,7 +9,9 @@
 
 #include <string.h>
 #include <unistd.h>
-
+#include <dlfcn.h>
+#include <elf.h>
+#include <link.h>
 #include "log.h"
 #include "utils.h"
 
@@ -20,6 +22,35 @@
  * \brief IPA Proxy
  */
 
+static bool isLibcameraInstalled()
+{
+	/* musl doesn't declare _DYNAMIC in link.h, declare it manually. */
+	extern ElfW(Dyn) _DYNAMIC[];
+
+	/*
+	 * DT_RUNPATH (DT_RPATH when the linker uses old dtags) is removed on
+	 * install.
+	 */
+	for (const ElfW(Dyn) *dyn = _DYNAMIC; dyn->d_tag != DT_NULL; ++dyn) {
+		if (dyn->d_tag == DT_RUNPATH || dyn->d_tag == DT_RPATH)
+			return false;
+	}
+
+	return true;
+}
+
+static std::string libcameraPath()
+{
+	Dl_info info;
+
+	/* Look up our own symbol. */
+	int ret = dladdr(reinterpret_cast<void *>(libcameraPath), &info);
+	if (ret == 0)
+		return nullptr;
+
+	return info.dli_fname;
+}
+
 namespace libcamera {
 
 LOG_DEFINE_CATEGORY(IPAProxy)
@@ -89,10 +120,23 @@ std::string IPAProxy::resolvePath(const std::string &file) const
 		}
 	}
 
-	/*Try finding the exec target from the install directory.*/
-        std::string proxyPath = std::string(IPA_PROXY_DIR) + proxyFile;
-        if (!access(proxyPath.c_str(), X_OK))
-                return proxyPath;
+	/*
+	 *When libcamera is used before it is installed, load proxies from the
+	 *same build directory as the libcamera directory itself. This requires
+	 *identifying the path of the libcamera.so, and referencing a relative
+	 *path for the proxies from that point.
+	 */
+	if (!isLibcameraInstalled()){
+		std::string ipaProxyDir = utils::dirname(libcameraPath()) + "/../../proxy";
+
+		LOG(IPAProxy, Info)
+			<< "libcamera is not installed. Adding '"
+			<< ipaProxyDir << "' to the Proxy search path";
+
+		std::string proxyPath = ipaProxyDir + proxyFile;
+		if (!access(proxyPath.c_str(), X_OK))
+			return proxyPath;
+	}
 
 	return std::string();
 }
-- 
2.17.1