emit license

Author: varun-r-mallya

examples/c-form/Makefile

@@ -3,13 +3,17 @@ CFLAGS := -O2 -emit-llvm -target bpf -c
 
 SRC := example.bpf.c
 OUT := example.bpf.ll
+OBJECT := example.bpf.o
 
 .PHONY: all clean
 
 all: $(OUT)
+	
+object: $(SRC)
+	$(BPF_CLANG) $(CFLAGS) $< -o $(OBJECT)
 
-$(OUT): $(SRC)
+$(OUT): $(SRC) object
 	$(BPF_CLANG) $(CFLAGS) -S $< -o $@
 
 clean:
-	rm -f $(OUT)
+	rm -f $(OUT) $(OBJECT)

examples/execve.py

@@ -1,8 +1,8 @@
-from pythonbpf.decorators import tracepoint, license
+from pythonbpf.decorators import tracepoint
 
 @tracepoint("syscalls:sys_enter_execve")
 def trace_execve(ctx) -> int:
     print("execve called\n")
     return 0
 
-license("GPL")
+LICENSE = "GPL"

pythonbpf/codegen.py

@@ -1,28 +1,20 @@
 import ast
 from llvmlite import ir
+from .license_pass import license_processing
 
-def parser(source_code, filename):
+def processor(source_code, filename, module):
     tree = ast.parse(source_code, filename)
-
-    for node in tree.body:
-        if isinstance(node, ast.FunctionDef):
-            print("Function:", node.name)
-            for dec in node.decorator_list:
-                print("  Decorator AST:", ast.dump(dec))
+    license_processing(tree, module)
 
 def compile_to_ir(filename: str, output: str):
     with open(filename) as f:
-        parser(f.read(), filename)
+        source = f.read()
+
     module = ir.Module(name=filename)
     module.data_layout = "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128"
     module.triple = "bpf"
 
-    func_ty = ir.FunctionType(ir.IntType(64), [], False)
-    func = ir.Function(module, func_ty, name="trace_execve")
-
-    block = func.append_basic_block(name="entry")
-    builder = ir.IRBuilder(block)
-    builder.ret(ir.IntType(64)(0))
+    processor(source, filename, module)
 
     with open(output, "w") as f:
         f.write(str(module))

pythonbpf/decorators.py

@@ -3,6 +3,3 @@ def wrapper(fn):
         fn._section = f"tracepoint/{name}"
         return fn
     return wrapper
-
-def license(license_type: str):
-    return license_type

pythonbpf/license_pass.py

@@ -0,0 +1,33 @@
+from llvmlite import ir
+import ast
+
+def emit_license(module: ir.Module, license_str: str):
+    license_bytes = license_str.encode("utf8") + b"\x00"
+    elems = [ir.Constant(ir.IntType(8), b) for b in license_bytes]
+    ty = ir.ArrayType(ir.IntType(8), len(elems))
+
+    gvar = ir.GlobalVariable(module, ty, name="LICENSE")
+
+    gvar.initializer = ir.Constant(ty, elems)  # type: ignore
+
+    gvar.align = 1                      # type: ignore
+    gvar.linkage = "dso_local"          # type: ignore
+    gvar.global_constant = False        # must be global, not constant
+    gvar.section = "license"            # type: ignore
+
+    return gvar
+
+def license_processing(tree, module):
+    count = 0
+    for node in tree.body:
+        if isinstance(node, ast.Assign):
+            for target in node.targets:
+                if isinstance(target, ast.Name) and target.id == "LICENSE":
+                    if count == 0:
+                        count += 1
+                        if isinstance(node.value, ast.Constant) and isinstance(node.value.value, str):
+                            emit_license(module, node.value.value)
+                        else:
+                            print("ERROR: LICENSE must be a string literal")
+                    else:
+                        print("ERROR: LICENSE already assigned")