Improve initialization warnings.

lib/cl/api.jl

@@ -71,15 +71,85 @@ end
 
 include("libopencl.jl")
 
+@static if Sys.iswindows()
+    # Windows type aliases
+    const BOOL = Int32
+    const DWORD = UInt32
+    const PDWORD = Ptr{DWORD}
+    const HANDLE = Ptr{Cvoid}
+    const PHANDLE = Ptr{HANDLE}
+    const BYTE = UInt8
+    const PBYTE = Ptr{BYTE}
+    const PVOID = Ptr{Cvoid}
+    const PSID = PVOID
+    const PSID_AND_ATTRIBUTES = PVOID
+    struct SID_AND_ATTRIBUTES
+        Sid::PSID
+        Attributes::DWORD
+    end
+    struct TOKEN_MANDATORY_LABEL
+        Label::SID_AND_ATTRIBUTES
+    end
+
+    # Windows constants
+    const TOKEN_QUERY = DWORD(0x0008)
+    const TOKEN_QUERY_SOURCE = DWORD(0x0010)
+    const SECURITY_MAX_SID_SIZE = 68
+    const SECURITY_MANDATORY_MEDIUM_RID = DWORD(0x2000)
+    const TokenIntegrityLevel = 25  # TOKEN_INFORMATION_CLASS enum value
+
+    const kernel32 = "kernel32.dll"
+    GetCurrentProcess() = @ccall kernel32.GetCurrentProcess()::HANDLE
+    CloseHandle(hObject) = @ccall kernel32.CloseHandle(hObject::HANDLE)::BOOL
+
+    const advapi32 = "advapi32.dll"
+    OpenProcessToken(ProcessHandle, DesiredAccess, TokenHandle) =
+        @ccall advapi32.OpenProcessToken(ProcessHandle::HANDLE, DesiredAccess::DWORD, TokenHandle::PHANDLE)::BOOL
+    GetTokenInformation(TokenHandle, TokenInformationClass, TokenInformation, TokenInformationLength, ReturnLength) =
+        @ccall advapi32.GetTokenInformation(TokenHandle::HANDLE, TokenInformationClass::Int32, TokenInformation::PBYTE, TokenInformationLength::DWORD, ReturnLength::PDWORD)::BOOL
+    GetSidSubAuthorityCount(pSid) =
+        @ccall advapi32.GetSidSubAuthorityCount(pSid::PSID)::PBYTE
+    GetSidSubAuthority(pSid, nSubAuthority) =
+        @ccall advapi32.GetSidSubAuthority(pSid::PSID, nSubAuthority::DWORD)::PDWORD
+
+    # mimics `khrIcd_IsHighIntegrityLevel`, which determines if we can specify
+    # drivers through environment variables
+    function is_high_integrity_level()::Bool
+        is_high_integrity = false
+
+        h_token = Ref{HANDLE}()
+        if OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY | TOKEN_QUERY_SOURCE, h_token) != 0
+            try
+                # Maximum possible size of SID_AND_ATTRIBUTES is maximum size of a SID + size of attributes DWORD.
+                mandatory_label_buffer = zeros(BYTE, SECURITY_MAX_SID_SIZE + sizeof(DWORD))
+                buffer_size = Ref{DWORD}()
+                if GetTokenInformation(h_token[], TokenIntegrityLevel, mandatory_label_buffer, length(mandatory_label_buffer), buffer_size) != 0
+                    mandatory_label = unsafe_load(Ptr{TOKEN_MANDATORY_LABEL}(pointer(mandatory_label_buffer)))
+                    sub_auth_count = unsafe_load(GetSidSubAuthorityCount(mandatory_label.Label.Sid))
+                    integrity_level = unsafe_load(GetSidSubAuthority(mandatory_label.Label.Sid, sub_auth_count - 1))
+
+                    return integrity_level > SECURITY_MANDATORY_MEDIUM_RID
+                end
+            finally
+                CloseHandle(h_token[])
+            end
+        end
+
+        return is_high_integrity
+    end
+end
+
 # lazy initialization
 const initialized = Ref{Bool}(false)
 @noinline function initialize()
     initialized[] = true
 
-    if isempty(OpenCL_jll.drivers)
-        @warn """No OpenCL driver JLLs were detected at the time of the first call into OpenCL.jl.
-                 Only system drivers will be available."""
-        return
+    @static if Sys.iswindows()
+        if is_high_integrity_level()
+            @warn """Running at high integrity level, preventing OpenCL.jl from loading drivers from JLLs.
+
+                     Only system drivers will be available. To enable JLL drivers, do not run Julia as an administrator."""
+        end
     end
 
     ocd_filenames = join(OpenCL_jll.drivers, ':')
@@ -92,6 +162,13 @@ const initialized = Ref{Bool}(false)
         @ccall libopencl.clGetPlatformIDs(
             0::cl_uint, C_NULL::Ptr{cl_platform_id},
             num_platforms::Ptr{cl_uint})::cl_int
+
+        if num_platforms[] == 0 && isempty(OpenCL_jll.drivers)
+            @error """No OpenCL drivers available, either system-wide or provided by a JLL.
+
+                      Please install a system-wide OpenCL driver, or load one together with OpenCL.jl,
+                      e.g., by doing `using OpenCL, pocl_jll`."""
+        end
     end
 end