Add CodeQL query to detect redundant assignments

Signed-off-by: Richard Yao <[email protected]>

.github/codeql-cpp.yml

@@ -0,0 +1,5 @@
+name: "Custom CodeQL Analysis"
+
+queries:
+  - uses: ./.github/codeql/custom-queries/cpp/deprecatedFunctionUsage.ql
+#  - uses: ./.github/codeql/openzfs-code-scanning.qls

.github/codeql-python.yml

@@ -0,0 +1,4 @@
+name: "Custom CodeQL Analysis"
+
+paths-ignore:
+  - tests

.github/codeql/custom-queries/cpp/deprecatedFunctionUsage.ql

@@ -0,0 +1,50 @@
+/**
+ * @name Deprecated function usage detection
+ * @description Detects functions whose usage is banned from the OpenZFS
+ *              codebase due to QA concerns.
+ * @kind problem
+ * @severity error
+ * @id cpp/deprecated-function-usage
+*/
+
+import cpp
+
+predicate isDeprecatedFunction(Function f) {
+  f.getName() = "strtok" or
+  f.getName() = "__xpg_basename" or
+  f.getName() = "basename" or
+  f.getName() = "dirname" or
+  f.getName() = "bcopy" or
+  f.getName() = "bcmp" or
+  f.getName() = "bzero" or
+  f.getName() = "asctime" or
+  f.getName() = "asctime_r"
+}
+
+string getReplacementMessage(Function f) {
+  if f.getName() = "strtok" then
+    result = "strtok_r(3)"
+  else if f.getName() = "__xpg_basename" then
+    result = "zfs_basename()"
+  else if f.getName() = "basename" then
+    result = "zfs_basename()"
+  else if f.getName() = "dirname" then
+    result = "zfs_dirnamelen()"
+  else if f.getName() = "bcopy" then
+    result = "memcpy(3)/memmove(3)"
+  else if f.getName() = "bcmp" then
+    result = "memcmp(3)"
+  else if f.getName() = "bzero" then
+    result = "memset(3)"
+  else if f.getName() = "asctime" then
+    result = "strftime(3)"
+  else
+    result = "strftime(3)"
+}
+
+from FunctionCall fc, Function f
+where
+  fc.getTarget() = f and
+  isDeprecatedFunction(f)
+select fc, "Usage of '" + f.getName() + "' is deprecated, consider using '" +
+  getReplacementMessage(f) + "' instead."

.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

.github/codeql/openzfs-code-scanning.qls

@@ -0,0 +1,3 @@
+# Reusing existing QL Pack
+- import: codeql-suites/cpp-code-scanning.qls
+  from: codeql-cpp

.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