Detect noexec and report a better error

This will bubble up a much more informative error message if noexec
is preventing us from running the subprocess

llm/server.go

@@ -307,6 +307,11 @@ func NewLlamaServer(gpus gpu.GpuInfoList, model string, ggml *GGML, adapters, pr
 		slog.Debug("subprocess", "environment", s.cmd.Env)
 
 		if err = s.cmd.Start(); err != nil {
+			// Detect permission denied and augment them essage about noexec
+			if errors.Is(err, os.ErrPermission) {
+				finalErr = fmt.Errorf("unable to start server %w.  %s may have noexec set.  Set OLLAMA_TMPDIR for server to a writable executable directory", err, dir)
+				continue
+			}
 			msg := ""
 			if s.status != nil && s.status.LastErrMsg != "" {
 				msg = s.status.LastErrMsg
@@ -382,6 +387,10 @@ func (s *llmServer) getServerStatus(ctx context.Context) (ServerStatus, error) {
 		if s.status != nil && s.status.LastErrMsg != "" {
 			msg = s.status.LastErrMsg
 		}
+		if s.cmd.ProcessState.ExitCode() == -1 {
+			// Most likely a signal killed it, log some more details to try to help troubleshoot
+			slog.Warn("llama runner process no longer running", "sys", s.cmd.ProcessState.Sys(), "string", s.cmd.ProcessState.String())
+		}
 		return ServerStatusError, fmt.Errorf("llama runner process no longer running: %d %s", s.cmd.ProcessState.ExitCode(), msg)
 	}