Update flake (#34)

* Improve kernel tests execution with nix

Rather than the hack of hardcoding nix store hashes which worked by
sheer luck, leverage nix (the build system) to pull in the right
dependencies and produce the appropriate artifacts.

Test Plan
=========

CI + run it locally with `nix run .#vmtest`

* Update nix flakes

And add file type suffix to cargo config.

Test Plan
=========

CI

.github/workflows/vmtests.yml

@@ -24,11 +24,5 @@ jobs:
         export DEBIAN_FRONTEND=noninteractive
         sudo apt-get -y install --no-install-recommends qemu-system-x86 qemu-guest-agent
 
-    - name: Set up nix dev env
-      run: nix develop --command echo 0
-
-    - name: Build `lightswitch`
-      run: nix develop --ignore-environment --command bash -c 'cargo build'
-
     - name: Run kernel tests
-      run: nix develop --command 'vmtest'
+      run: nix run .#vmtest

flake.nix

@@ -40,7 +40,7 @@
           nativeBuildInputs = with pkgs; [
             pkg-config
           ];
-          craneLib = crane.lib.${system};
+          craneLib = (crane.mkLib nixpkgs.legacyPackages.${system});
           lightswitch = craneLib.buildPackage {
             src = ./.;
             doCheck = false;
@@ -64,6 +64,7 @@
                 ];
               };
             };
+            vmtest = (import ./vm.nix { inherit pkgs; }).run-vmtest lightswitch;
           };
           devShells.default = mkShell {
             nativeBuildInputs = nativeBuildInputs;
@@ -79,13 +80,6 @@
               # snapshot testing plugin binary
               cargo-insta
               # ocamlPackages.magic-trace
-              (import ./vm.nix { inherit pkgs; }).vmtest
-              (import ./vm.nix { inherit pkgs; }).kernel_5_15
-              (import ./vm.nix { inherit pkgs; }).kernel_6_0
-              (import ./vm.nix { inherit pkgs; }).kernel_6_2
-              (import ./vm.nix { inherit pkgs; }).kernel_6_6
-              (import ./vm.nix { inherit pkgs; }).kernel_6_8_7
-              (import ./vm.nix { inherit pkgs; }).kernel_6_9_rc5
             ];
 
             LIBCLANG_PATH = lib.makeLibraryPath [ llvmPackages_16.libclang ];

src/main.rs

@@ -83,6 +83,14 @@ enum LoggingLevel {
     Error,
 }
 
+#[derive(clap::ValueEnum, Debug, Clone, Default)]
+enum ProfileFormat {
+    #[default]
+    FlameGraph,
+    /// Do not produce a profile. Used for kernel tests.
+    None,
+}
+
 #[derive(Parser, Debug)]
 struct Cli {
     /// Specific PIDs to profile
@@ -93,13 +101,13 @@ struct Cli {
     tids: Vec<i32>,
     /// Show unwind info for given binary
     #[arg(long, value_name = "PATH_TO_BINARY",
-        conflicts_with_all = ["pids", "tids", "show_info", "duration", "sample_freq", "flamegraph_file"]
+        conflicts_with_all = ["pids", "tids", "show_info", "duration", "sample_freq", "profile_name"]
     )]
     show_unwind_info: Option<String>,
     /// Show build ID for given binary
     #[arg(long, value_name = "PATH_TO_BINARY",
         conflicts_with_all = ["pids", "tids", "duration",
-            "sample_freq", "flamegraph_file"]
+            "sample_freq", "profile_name"]
     )]
     show_info: Option<String>,
     /// How long this agent will run in seconds
@@ -123,8 +131,12 @@ struct Cli {
     )]
     sample_freq: u16,
     /// Output file for Flame Graph in SVG format
+    #[arg(long, default_value_t, value_enum)]
+    profile_format: ProfileFormat,
+    /// Name for the generated profile.
+    // TODO: change suffix depending on the format.
     #[arg(long, default_value = "flame.svg")]
-    flamegraph_file: PathBuf,
+    profile_name: PathBuf,
 }
 
 /// Exit the main thread if any thread panics. We prefer this behaviour because pretty much every
@@ -297,16 +309,22 @@ fn main() -> Result<(), Box<dyn Error>> {
         }
     }
 
-    let mut options: flamegraph::Options<'_> = flamegraph::Options::default();
-    let data = folded.as_bytes();
-    let flame_path = args.flamegraph_file;
-    let f = File::create(flame_path).unwrap();
-    match flamegraph::from_reader(&mut options, data, f) {
-        Ok(_) => {
-            eprintln!("Profile successfully written to disk");
+    match args.profile_format {
+        ProfileFormat::FlameGraph => {
+            let mut options: flamegraph::Options<'_> = flamegraph::Options::default();
+            let data = folded.as_bytes();
+            let f = File::create(args.profile_name).unwrap();
+            match flamegraph::from_reader(&mut options, data, f) {
+                Ok(_) => {
+                    eprintln!("Profile successfully written to disk");
+                }
+                Err(e) => {
+                    error!("Failed generate profile: {:?}", e);
+                }
+            }
         }
-        Err(e) => {
-            error!("Failed generate profile: {:?}", e);
+        ProfileFormat::None => {
+            // Do nothing
         }
     }
 
@@ -335,7 +353,7 @@ mod tests {
         let actual = String::from_utf8(cmd.unwrap().stdout).unwrap();
         insta::assert_yaml_snapshot!(actual, @r###"
         ---
-        "Usage: lightswitch [OPTIONS]\n\nOptions:\n      --pids <PIDS>\n          Specific PIDs to profile\n      --tids <TIDS>\n          Specific TIDs to profile (these can be outside the PIDs selected above)\n      --show-unwind-info <PATH_TO_BINARY>\n          Show unwind info for given binary\n      --show-info <PATH_TO_BINARY>\n          Show build ID for given binary\n  -D, --duration <DURATION>\n          How long this agent will run in seconds [default: 18446744073709551615]\n      --libbpf-logs\n          Enable libbpf logs. This includes the BPF verifier output\n      --bpf-logging\n          Enable BPF programs logging\n      --logging <LOGGING>\n          Set lightswitch's logging level [default: info] [possible values: trace, debug, info, warn, error]\n      --sample-freq <SAMPLE_FREQ_IN_HZ>\n          Per-CPU Sampling Frequency in Hz [default: 19]\n      --flamegraph-file <FLAMEGRAPH_FILE>\n          Output file for Flame Graph in SVG format [default: flame.svg]\n  -h, --help\n          Print help\n"
+        "Usage: lightswitch [OPTIONS]\n\nOptions:\n      --pids <PIDS>\n          Specific PIDs to profile\n\n      --tids <TIDS>\n          Specific TIDs to profile (these can be outside the PIDs selected above)\n\n      --show-unwind-info <PATH_TO_BINARY>\n          Show unwind info for given binary\n\n      --show-info <PATH_TO_BINARY>\n          Show build ID for given binary\n\n  -D, --duration <DURATION>\n          How long this agent will run in seconds\n          \n          [default: 18446744073709551615]\n\n      --libbpf-logs\n          Enable libbpf logs. This includes the BPF verifier output\n\n      --bpf-logging\n          Enable BPF programs logging\n\n      --logging <LOGGING>\n          Set lightswitch's logging level\n          \n          [default: info]\n          [possible values: trace, debug, info, warn, error]\n\n      --sample-freq <SAMPLE_FREQ_IN_HZ>\n          Per-CPU Sampling Frequency in Hz\n          \n          [default: 19]\n\n      --profile-format <PROFILE_FORMAT>\n          Output file for Flame Graph in SVG format\n          \n          [default: flame-graph]\n\n          Possible values:\n          - flame-graph\n          - none:        Do not produce a profile. Used for kernel tests\n\n      --profile-name <PROFILE_NAME>\n          Name for the generated profile\n          \n          [default: flame.svg]\n\n  -h, --help\n          Print help (see a summary with '-h')\n"
         "###);
     }
 

vm.nix

@@ -1,5 +1,6 @@
 { pkgs }:
-{
+let
+
   kernel_5_15 = pkgs.stdenv.mkDerivation {
     name = "download-kernel-5.15";
     src = pkgs.fetchurl {
@@ -78,6 +79,48 @@
     '';
   };
 
+  vmtest-create-config = lightswitch: pkgs.stdenv.mkDerivation {
+    name = "vmtest-dump-config";
+    dontUnpack = true;
+
+    src = pkgs.writeText "vmtest.toml" ''
+      [[target]]
+      name = "Fedora 5.15"
+      kernel = "${kernel_5_15}/bzImage"
+      command = "${lightswitch}/bin/lightswitch --duration 0 --profile-format=none"
+
+      [[target]]
+      name = "Fedora 6.0"
+      kernel = "${kernel_6_0}/bzImage"
+      command = "${lightswitch}/bin/lightswitch --duration 0 --profile-format=none"
+
+      [[target]]
+      name = "Fedora 6.2"
+      kernel = "${kernel_6_2}/bzImage"
+      command = "${lightswitch}/bin/lightswitch --duration 0 --profile-format=none"
+
+      [[target]]
+      name = "Fedora 6.6"
+      kernel = "${kernel_6_6}/bzImage"
+      command = "${lightswitch}/bin/lightswitch --duration 0 --profile-format=none"
+
+      [[target]]
+      name = "Upstream 6.8.7"
+      kernel = "${kernel_6_8_7}/bzImage"
+      command = "${lightswitch}/bin/lightswitch --duration 0 --profile-format=none"
+
+      [[target]]
+      name = "Upstream v6.9-rc5"
+      kernel = "${kernel_6_9_rc5}/bzImage"
+      command = "${lightswitch}/bin/lightswitch --duration 0 --profile-format=none"
+    '';
+    nativeBuildInputs = [ ];
+    installPhase = ''
+      mkdir -p $out
+      cp -r $src $out/vmtest.toml
+    '';
+  };
+
   vmtest = pkgs.rustPlatform.buildRustPackage {
     name = "vmtest";
     src = pkgs.fetchFromGitHub {
@@ -101,4 +144,10 @@
       platforms = platforms.linux;
     };
   };
+in
+{
+  run-vmtest = lightswitch:
+    pkgs.writeShellScriptBin "run-vmtests" ''
+      ${vmtest}/bin/vmtest --config ${vmtest-create-config lightswitch}/vmtest.toml
+    '';
 }