Add kernel tests

.github/workflows/vmtests.yml

@@ -0,0 +1,34 @@
+name: vmtests
+on:
+    pull_request:
+    push:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  vmtests:
+    runs-on: ubuntu-22.04
+    permissions:
+        id-token: write
+        contents: read
+
+    steps:
+    - uses: actions/checkout@main
+    - uses: DeterminateSystems/nix-installer-action@main
+    - uses: DeterminateSystems/magic-nix-cache-action@main
+
+    - name: Install system dependencies
+      run: |
+        export DEBIAN_FRONTEND=noninteractive
+        sudo apt-get update && 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'

.gitignore

@@ -1,3 +1,4 @@
 /target
 flame.svg
 src/bpf/*_skel.rs
+.vmtest.log

flake.nix

@@ -53,6 +53,11 @@
               # 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
             ];
 
             LIBCLANG_PATH = lib.makeLibraryPath [ llvmPackages_16.libclang ];

src/profiler.rs

@@ -588,6 +588,8 @@ impl Profiler<'_> {
         }
     }
 
+    // Adds a mapping key to the LPM trie. This could either be an executable mapping
+    // or just a pid with a mapping set to zero and the appropriate prefix.
     fn add_bpf_mapping(
         &mut self,
         key: &exec_mappings_key,
@@ -910,17 +912,11 @@ impl Profiler<'_> {
         if have_unwind_info {
             self.native_unwind_state.dirty = true;
 
-            // Add entry just with the pid to signal processes that we already know about.
-            let key = exec_mappings_key::new(
-                pid.try_into().unwrap(),
-                0x0,
-                32, // pid bits
-            );
-            self.add_bpf_mapping(&key, &mapping_t::default()).unwrap();
-
             // Add process info
             for mapping in mappings {
-                for address_range in summarize_address_range(mapping.begin, mapping.end - 1) {
+                let lpm_range = summarize_address_range(mapping.begin, mapping.end - 1);
+                debug!("Adding {} entries to the LPM trie", lpm_range.len());
+                for address_range in lpm_range {
                     let key = exec_mappings_key::new(
                         pid.try_into().unwrap(),
                         address_range.addr,
@@ -930,6 +926,15 @@ impl Profiler<'_> {
                     self.add_bpf_mapping(&key, &mapping).unwrap();
                 }
             }
+
+            // Once all the executable mappings are updated, add entry just with the pid
+            // to signal that is a known process.
+            let key = exec_mappings_key::new(
+                pid.try_into().unwrap(),
+                0x0,
+                32, // number of bits for pids
+            );
+            self.add_bpf_mapping(&key, &mapping_t::default()).unwrap();
         }
     }
 

vm.nix

@@ -0,0 +1,78 @@
+{ pkgs }:
+{
+  kernel_5_15 = pkgs.stdenv.mkDerivation {
+    name = "download-kernel-5.15";
+    src = pkgs.fetchurl {
+      url = "https://github.com/danobi/vmtest/releases/download/test_assets/bzImage-v5.15-fedora38";
+      hash = "sha256-nq8W72vuNKCgO1OS6aJtAfg7AjHavRZ7WAkP7X6V610=";
+    };
+    dontUnpack = true;
+    installPhase = ''
+      mkdir -p $out
+      cp -r $src $out/bzImage
+    '';
+  };
+
+  kernel_6_0 = pkgs.stdenv.mkDerivation {
+    name = "download-kernel-6.0";
+    src = pkgs.fetchurl {
+      url = "https://github.com/danobi/vmtest/releases/download/test_assets/bzImage-v6.0-fedora38";
+      hash = "sha256-ZBBQ0yVUn+Isd2b+a32oMEbNo8T1v46P3rEtZ+1j9Ic=";
+    };
+    dontUnpack = true;
+    installPhase = ''
+      mkdir -p $out
+      cp -r $src $out/bzImage
+    '';
+  };
+
+  kernel_6_2 = pkgs.stdenv.mkDerivation {
+    name = "download-kernel-6.2";
+    src = pkgs.fetchurl {
+      url = "https://github.com/danobi/vmtest/releases/download/test_assets/bzImage-v6.2-fedora38";
+      hash = "sha256-YO2HEIWTuEEJts9JrW3V7UVR7t4J3+8On+tjdELa2m8=";
+    };
+    dontUnpack = true;
+    installPhase = ''
+      mkdir -p $out
+      cp -r $src $out/bzImage
+    '';
+  };
+
+  kernel_6_6 = pkgs.stdenv.mkDerivation {
+    name = "download-kernel-6.6";
+    src = pkgs.fetchurl {
+      url = "https://github.com/danobi/vmtest/releases/download/test_assets/bzImage-v6.6-fedora38";
+      hash = "sha256-6Fu16SPBITP0sI3lapkckZna6GKBn2hID038itt82jA=";
+    };
+    dontUnpack = true;
+    installPhase = ''
+      mkdir -p $out
+      cp -r $src $out/bzImage
+    '';
+  };
+
+  vmtest = pkgs.rustPlatform.buildRustPackage {
+    name = "vmtest";
+    src = pkgs.fetchFromGitHub {
+      owner = "danobi";
+      repo = "vmtest";
+      rev = "51f11bf301fea054342996802a16ed21fb5054f4";
+      sha256 = "sha256-qtTq0dnDHi1ITfQzKrXz+1dRMymAFBivWpjXntD09+A=";
+    };
+    cargoHash = "sha256-SHjjCWz4FVVk1cczkMltRVEB3GK8jz2tVABNSlSZiUc=";
+    # nativeCheckInputs = [ pkgs.qemu ];
+
+    # There are some errors trying to access `/build/source/tests/*`.
+    doCheck = false;
+
+    meta = with pkgs.lib; {
+      description = "Helps run tests in virtual machines";
+      homepage = "https://github.com/danobi/vmtest/";
+      license = licenses.asl20;
+      mainProgram = "";
+      maintainers = with maintainers; [ ];
+      platforms = platforms.linux;
+    };
+  };
+}

vmtest.toml

@@ -0,0 +1,19 @@
+[[target]]
+name = "Fedora 5.15"
+kernel = "/nix/store/cg9wq48zz2dbvayh7sigr5smaf4dwcxp-download-kernel-5.15/bzImage"
+command = "/mnt/vmtest/target/debug/lightswitch --duration 0"
+
+[[target]]
+name = "Fedora 6.0"
+kernel = "/nix/store/p8xc9gqdkpfjpmcb9ja2gx6g6bd9cby7-download-kernel-6.0/bzImage"
+command = "/mnt/vmtest/target/debug/lightswitch --duration 0"
+
+[[target]]
+name = "Fedora 6.2"
+kernel = "/nix/store/79wzcqy12fncdf6pk1fj627ggh7v0nc7-download-kernel-6.2/bzImage"
+command = "/mnt/vmtest/target/debug/lightswitch --duration 0"
+
+[[target]]
+name = "Fedora 6.6"
+kernel = "/nix/store/77ixckavs2qidx1pglmlxsj6bfvjqijb-download-kernel-6.6/bzImage"
+command = "/mnt/vmtest/target/debug/lightswitch --duration 0"