From 15545d95dc1ea55240f4be08c65f4ec64c46f49f Mon Sep 17 00:00:00 2001
From: Franck Cuny <franck@fcuny.net>
Date: Tue, 25 Oct 2022 19:33:09 -0700
Subject: ref(tools/perf-flamegraph): move to a proper shell script

I don't want to inline shell scripts inside nix configuration, as it
prevents me to use `shellcheck` to validate them for example.

The script is now moved into the tool directory, and is a tiny bit more
flexible, so that I can run it as my own user.
---
 modules/system/packages/default.nix              | 18 +++---------------
 tools/default.nix                                |  1 +
 tools/perf-flamegraph-pid/default.nix            | 24 ++++++++++++++++++++++++
 tools/perf-flamegraph-pid/perf-flamegraph-pid.sh | 20 ++++++++++++++++++++
 4 files changed, 48 insertions(+), 15 deletions(-)
 create mode 100644 tools/perf-flamegraph-pid/default.nix
 create mode 100755 tools/perf-flamegraph-pid/perf-flamegraph-pid.sh

diff --git a/modules/system/packages/default.nix b/modules/system/packages/default.nix
index 52ed7ca..78ab52f 100644
--- a/modules/system/packages/default.nix
+++ b/modules/system/packages/default.nix
@@ -3,20 +3,6 @@
 with lib;
 let
   linuxpkgs = config.boot.kernelPackages;
-  perf-flamegraph-process =
-    pkgs.writeShellScriptBin "perf-flamegraph-process" ''
-      set -euo pipefail
-
-      OUT_DIR="''${HOME}/workspace/tmp/flamegraph"
-      OUT_SVG="''${OUT_DIR}/$(date +%y%m%d-%H%M%S).svg"
-
-      mkdir -p ''${OUT_DIR}
-
-      ${pkgs.linuxPackages.perf}/bin/perf record -g --call-graph dwarf -F max "$@"
-      ${pkgs.linuxPackages.perf}/bin/perf script \
-        | ${pkgs.flamegraph}/bin/stackcollapse-perf.pl \
-        | ${pkgs.flamegraph}/bin/flamegraph.pl > "''${OUT_SVG}"
-    '';
 in
 {
 
@@ -48,7 +34,6 @@ in
     openssl.dev
     parted
     pciutils
-    perf-flamegraph-process
     perf-tools
     pkg-config
     powertop
@@ -63,6 +48,9 @@ in
     vim
     wget
     wireguard-tools
+
+    # my custom tools
+    tools.perf-flamegraph-pid
   ];
 
   programs.bcc.enable = true;
diff --git a/tools/default.nix b/tools/default.nix
index 543882f..7003b8a 100644
--- a/tools/default.nix
+++ b/tools/default.nix
@@ -8,4 +8,5 @@ pkgs.lib.makeScope pkgs.newScope (pkgs: {
   git-blame-stats = pkgs.callPackage ./git-blame-stats { };
   git-broom = pkgs.callPackage ./git-broom { };
   sendsms = pkgs.callPackage ./sendsms { };
+  perf-flamegraph-pid = pkgs.callPackage ./perf-flamegraph-pid { };
 })
diff --git a/tools/perf-flamegraph-pid/default.nix b/tools/perf-flamegraph-pid/default.nix
new file mode 100644
index 0000000..d3b3e1e
--- /dev/null
+++ b/tools/perf-flamegraph-pid/default.nix
@@ -0,0 +1,24 @@
+{ lib, stdenvNoCC, pkgs, config }:
+
+stdenvNoCC.mkDerivation rec {
+  pname = "perf-flamegraph-pid";
+  src = ./perf-flamegraph-pid.sh;
+  version = "0.1.0";
+
+  nativeBuildInputs = with pkgs; [ flamegraph linuxPackages_latest.perf ];
+
+  dontUnpack = true;
+  dontBuild = true;
+
+  installPhase = ''
+    mkdir -p $out/bin
+    cp $src $out/bin/${pname}
+  '';
+
+  meta = with lib; {
+    description = "Generate a process' flame graph.";
+    license = with licenses; [ mit ];
+    platforms = platforms.unix;
+    maintainers = with maintainers; [ fcuny ];
+  };
+}
diff --git a/tools/perf-flamegraph-pid/perf-flamegraph-pid.sh b/tools/perf-flamegraph-pid/perf-flamegraph-pid.sh
new file mode 100755
index 0000000..141ceec
--- /dev/null
+++ b/tools/perf-flamegraph-pid/perf-flamegraph-pid.sh
@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+OUT_DIR="${HOME}/workspace/debug/flamegraph"
+OUT_DATA="${OUT_DIR}/$(date +%y%m%d-%H%M%S).data"
+OUT_SVG="${OUT_DIR}/$(date +%y%m%d-%H%M%S).svg"
+
+mkdir -p "${OUT_DIR}"
+
+# record the data with perf. We need to run this with sudo to get all
+# the privileges we need.
+sudo perf record -g --call-graph dwarf --freq max --output "${OUT_DATA}" "$@"
+
+# give me ownership of the file
+sudo chown "${USER}" "${OUT_DATA}"
+
+perf script --input "${OUT_DATA}" | \
+     stackcollapse-perf.pl | \
+     flamegraph.pl > "${OUT_SVG}"
-- 
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