From 49969e952291bcaedf836d88d80618f9f8b75429 Mon Sep 17 00:00:00 2001
From: Richard Yao <richard.yao@alumni.stonybrook.edu>
Date: Sun, 21 Jan 2024 12:26:22 -0500
Subject: [PATCH] Add CodeQL query to detect redundant assignments

Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
---
 .github/codeql-cpp.yml                        |  5 ++++
 .github/codeql-python.yml                     |  4 +++
 .github/codeql/custom-queries/cpp/qlpack.yml  |  4 +++
 .../custom-queries/cpp/redundantAssignment.c  |  8 ++++++
 .../custom-queries/cpp/redundantAssignment.ql | 26 +++++++++++++++++++
 .github/codeql/openzfs-code-scanning.qls      |  3 +++
 .github/workflows/codeql.yml                  |  1 +
 7 files changed, 51 insertions(+)
 create mode 100644 .github/codeql-cpp.yml
 create mode 100644 .github/codeql-python.yml
 create mode 100644 .github/codeql/custom-queries/cpp/qlpack.yml
 create mode 100644 .github/codeql/custom-queries/cpp/redundantAssignment.c
 create mode 100644 .github/codeql/custom-queries/cpp/redundantAssignment.ql
 create mode 100644 .github/codeql/openzfs-code-scanning.qls

diff --git a/.github/codeql-cpp.yml b/.github/codeql-cpp.yml
new file mode 100644
index 000000000000..48e86cdc28a1
--- /dev/null
+++ b/.github/codeql-cpp.yml
@@ -0,0 +1,5 @@
+name: "Custom CodeQL Analysis"
+
+queries:
+  - uses: ./.github/codeql/custom-queries/cpp/redundantAssignment.ql
+  - uses: ./.github/codeql/openzfs-code-scanning.qls
diff --git a/.github/codeql-python.yml b/.github/codeql-python.yml
new file mode 100644
index 000000000000..93cb4a435ed9
--- /dev/null
+++ b/.github/codeql-python.yml
@@ -0,0 +1,4 @@
+name: "Custom CodeQL Analysis"
+
+paths-ignore:
+  - tests
diff --git a/.github/codeql/custom-queries/cpp/qlpack.yml b/.github/codeql/custom-queries/cpp/qlpack.yml
new file mode 100644
index 000000000000..cbe0f1cbe3c4
--- /dev/null
+++ b/.github/codeql/custom-queries/cpp/qlpack.yml
@@ -0,0 +1,4 @@
+name: openzfs-cpp-queries
+version: 0.0.0
+libraryPathDependencies: codeql-cpp
+suites: openzfs-cpp-suite
diff --git a/.github/codeql/custom-queries/cpp/redundantAssignment.c b/.github/codeql/custom-queries/cpp/redundantAssignment.c
new file mode 100644
index 000000000000..f5c908a95090
--- /dev/null
+++ b/.github/codeql/custom-queries/cpp/redundantAssignment.c
@@ -0,0 +1,8 @@
+int
+main(void) {
+	int a = 0;
+	int b = a;
+	int c = 1;
+	a = b;
+	return (a*b*c);
+}
diff --git a/.github/codeql/custom-queries/cpp/redundantAssignment.ql b/.github/codeql/custom-queries/cpp/redundantAssignment.ql
new file mode 100644
index 000000000000..15a2cbc6877e
--- /dev/null
+++ b/.github/codeql/custom-queries/cpp/redundantAssignment.ql
@@ -0,0 +1,26 @@
+/**
+ * @name Redundant assignment detection
+ * @description Detects redundant assignments like 'a = b;' followed by 'b = a;' without any modification in between.
+ * @kind problem
+ * @id cpp/redundant-assignment
+ */
+
+import cpp
+
+from Assignment firstAssign, Assignment secondAssign
+where
+  // The first assignment is from 'a' to 'b'
+  firstAssign.getLValue().(VariableAccess).getTarget() = secondAssign.getRValue().(VariableAccess).getTarget() and
+  firstAssign.getRValue().(VariableAccess).getTarget() = secondAssign.getLValue().(VariableAccess).getTarget() and
+  // Ensure 'a' and 'b' are not modified in between these assignments
+  not exists(Assignment anyAssign |
+    anyAssign.getEnclosingFunction() = firstAssign.getEnclosingFunction() and
+    anyAssign.getLocation().getFile() = firstAssign.getLocation().getFile() and
+    anyAssign.getLocation().getStartLine() > firstAssign.getLocation().getStartLine() and
+    anyAssign.getLocation().getStartLine() < secondAssign.getLocation().getStartLine() and
+    (
+      anyAssign.getLValue().(VariableAccess).getTarget() = firstAssign.getLValue().(VariableAccess).getTarget() or
+      anyAssign.getLValue().(VariableAccess).getTarget() = firstAssign.getRValue().(VariableAccess).getTarget()
+    )
+  )
+select secondAssign, "This assignment is redundant."
diff --git a/.github/codeql/openzfs-code-scanning.qls b/.github/codeql/openzfs-code-scanning.qls
new file mode 100644
index 000000000000..c371ed848cf8
--- /dev/null
+++ b/.github/codeql/openzfs-code-scanning.qls
@@ -0,0 +1,3 @@
+# Reusing existing QL Pack
+- import: codeql-suites/cpp-code-scanning.qls
+  from: codeql-cpp
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 037f8aca0eaa..7ccfc1492564 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -29,6 +29,7 @@ jobs:
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v2
       with:
+        config-file: .github/codeql-${{ matrix.language }}.yml
         languages: ${{ matrix.language }}
 
     - name: Autobuild