basic ICD loader env var support for OCL_ICD_VENDORS

Author: bashbaug

CMakeLists.txt

@@ -33,6 +33,12 @@ find_package (Threads REQUIRED)
 # advance. Use it with discretion.
 option (BUILD_SHARED_LIBS "Build shared libs" ON)
 
+include(CheckFunctionExists)
+check_function_exists(secure_getenv HAVE_SECURE_GETENV)
+check_function_exists(__secure_getenv HAVE___SECURE_GETENV)
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/loader/icd_cmake_config.h.in
+    ${CMAKE_CURRENT_BINARY_DIR}/icd_cmake_config.h)
+
 set (OPENCL_ICD_LOADER_SOURCES
     loader/icd.c
     loader/icd_dispatch.c)
@@ -108,7 +114,7 @@ endif ()
 include_directories (${OPENCL_ICD_LOADER_HEADERS_DIR})
 add_definitions (-DCL_TARGET_OPENCL_VERSION=220)
 
-target_include_directories (OpenCL PRIVATE loader)
+target_include_directories (OpenCL PRIVATE ${CMAKE_CURRENT_BINARY_DIR} loader)
 target_link_libraries (OpenCL ${CMAKE_DL_LIBS})
 
 include (CTest)

loader/icd.h

@@ -19,6 +19,8 @@
 #ifndef _ICD_H_
 #define _ICD_H_
 
+#include "icd_cmake_config.h"
+
 #ifndef CL_USE_DEPRECATED_OPENCL_1_0_APIS
 #define CL_USE_DEPRECATED_OPENCL_1_0_APIS
 #endif

loader/icd_cmake_config.h.in

@@ -0,0 +1,2 @@
+#cmakedefine HAVE_SECURE_GETENV
+#cmakedefine HAVE___SECURE_GETENV

loader/icd_envvars.h

@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2016-2019 The Khronos Group Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * OpenCL is a trademark of Apple Inc. used under license by Khronos.
+ */
+
+#ifndef _ICD_ENVVARS_H_
+#define _ICD_ENVVARS_H_
+
+// Environment variables
+#if defined(__linux__) || defined(__APPLE__)
+
+static inline char *khrIcd_getenv(const char *name) {
+    // No allocation of memory necessary for Linux.
+    return getenv(name);
+}
+
+static inline char *khrIcd_secure_getenv(const char *name) {
+#if defined(__APPLE__)
+    // Apple does not appear to have a secure getenv implementation.
+    // The main difference between secure getenv and getenv is that secure getenv
+    // returns NULL if the process is being run with elevated privileges by a normal user.
+    // The idea is to prevent the reading of malicious environment variables by a process
+    // that can do damage.
+    // This algorithm is derived from glibc code that sets an internal
+    // variable (__libc_enable_secure) if the process is running under setuid or setgid.
+    return geteuid() != getuid() || getegid() != getgid() ? NULL : khrIcd_getenv(name);
+#else
+// Linux
+#ifdef HAVE_SECURE_GETENV
+    return secure_getenv(name);
+#elif defined(HAVE___SECURE_GETENV)
+    return __secure_getenv(name);
+#else
+#pragma message(                                                                       \
+    "Warning:  Falling back to non-secure getenv for environmental lookups!  Consider" \
+    " updating to a different libc.")
+    return khrIcd_getenv(name);
+#endif
+#endif
+}
+
+static inline void khrIcd_free_getenv(char *val) {
+    // No freeing of memory necessary for Linux, but we should at least touch
+    // val to get rid of compiler warnings.
+    (void)val;
+}
+
+#elif defined(WIN32)
+
+static inline char *khrIcd_getenv(const char *name) {
+    char *retVal;
+    DWORD valSize;
+
+    valSize = GetEnvironmentVariableA(name, NULL, 0);
+
+    // valSize DOES include the null terminator, so for any set variable
+    // will always be at least 1. If it's 0, the variable wasn't set.
+    if (valSize == 0) return NULL;
+
+    // Allocate the space necessary for the registry entry
+    retVal = (char *)malloc(valSize);
+
+    if (NULL != retVal) {
+        GetEnvironmentVariableA(name, retVal, valSize);
+    }
+
+    return retVal;
+}
+
+static inline char *khrIcd_secure_getenv(const char *name) {
+    // No secure version for Windows as far as I know
+    return khrIcd_getenv(name);
+}
+
+static inline void khrIcd_free_getenv(char *val) {
+    free((void *)val);
+}
+
+#else
+
+static inline char *khrIcd_getenv(const char *name) {
+    // stub func
+    (void)name;
+    return NULL;
+}
+static inline void khrIcd_free_getenv(char *val) {
+    // stub func
+    (void)val;
+}
+
+#endif
+
+#endif

loader/linux/icd_linux.c

@@ -16,7 +16,14 @@
  * OpenCL is a trademark of Apple Inc. used under license by Khronos.
  */
 
+// for secure_getenv():
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
 #include "icd.h"
+#include "icd_envvars.h"
+
 #include <dlfcn.h>
 #include <stdio.h>
 #include <string.h>
@@ -38,11 +45,15 @@ void khrIcdOsVendorsEnumerate(void)
 {
     DIR *dir = NULL;
     struct dirent *dirEntry = NULL;
+    char* vendorPath = khrIcd_secure_getenv("OCL_ICD_VENDORS");
+    if (vendorPath == NULL)
+    {
 #ifdef __ANDROID__
-    char *vendorPath = "/system/vendor/Khronos/OpenCL/vendors/";
+        vendorPath = "/system/vendor/Khronos/OpenCL/vendors/";
 #else
-    char *vendorPath = "/etc/OpenCL/vendors/";
+        vendorPath = "/etc/OpenCL/vendors/";
 #endif // ANDROID
+    }
 
     // open the directory
     dir = opendir(vendorPath);