add global support with broken generation function

Author: varun-r-mallya

pythonbpf/codegen.py

@@ -4,7 +4,7 @@
 from .functions_pass import func_proc
 from .maps import maps_proc
 from .structs import structs_proc
-from .globals_pass import globals_processing
+from .globals_pass import globals_list_creation, globals_processing
 from .debuginfo import DW_LANG_C11, DwarfBehaviorEnum, DebugInfoGenerator
 import os
 import subprocess
@@ -46,6 +46,7 @@ def processor(source_code, filename, module):
 
     license_processing(tree, module)
     globals_processing(tree, module)
+    globals_list_creation(tree, module)
 
 
 def compile_to_ir(filename: str, output: str, loglevel=logging.WARNING):

pythonbpf/globals_pass.py

@@ -1,8 +1,71 @@
 from llvmlite import ir
 import ast
 
+from llvmlite import ir
+import ast
+from logging import Logger
+import logging
+from .type_deducer import ctypes_to_ir
+
+logger: Logger = logging.getLogger(__name__)
+
+
+def emit_global(module: ir.Module, node, name):
+    print("global", node.returns.id)
+    ty = ctypes_to_ir(node.returns.id)
+
+    gvar = ir.GlobalVariable(module, ty, name=name)
+    gvar.initializer = ir.Constant(ty, initial_value)
+    gvar.align = 8
+    gvar.linkage = "dso_local"
+    gvar.global_constant = False
+    return gvar
 
-def emit_globals(module: ir.Module, names: list[str]):
+
+def globals_processing(tree, module):
+    """Process stuff decorated with @bpf and @bpfglobal except license and return the section name"""
+    global_sym_tab = []
+
+    for node in tree.body:
+        # Skip non-assignment and non-function nodes
+        if not (isinstance(node, (ast.FunctionDef, ast.AnnAssign, ast.Assign))):
+            continue
+
+        # Get the name based on node type
+        if isinstance(node, ast.FunctionDef):
+            name = node.name
+        else:
+            continue
+
+        # Check for duplicate names
+        if name in global_sym_tab:
+            raise SyntaxError(f"ERROR: Global name '{name}' previously defined")
+        else:
+            global_sym_tab.append(name)
+
+        # Process decorated functions
+        if isinstance(node, ast.FunctionDef) and node.name != "LICENSE":
+            # Check decorators
+            decorators = [
+                dec.id for dec in node.decorator_list if isinstance(dec, ast.Name)
+            ]
+
+            if "bpf" in decorators and "bpfglobal" in decorators:
+                if (
+                        len(node.body) == 1
+                        and isinstance(node.body[0], ast.Return)
+                        and node.body[0].value is not None
+                        and isinstance(node.body[0].value, (ast.Constant, ast.Name))
+                ):
+                    emit_global(module, node, name)
+                    return node.name
+                else:
+                    logger.info(f"Invalid global expression for '{node.name}'")
+                    return None
+
+    return None
+
+def emit_llvm_compiler_used(module: ir.Module, names: list[str]):
     """
     Emit the @llvm.compiler.used global given a list of function/global names.
     """
@@ -24,26 +87,27 @@ def emit_globals(module: ir.Module, names: list[str]):
     gv.section = "llvm.metadata"
 
 
-def globals_processing(tree, module: ir.Module):
+def globals_list_creation(tree, module: ir.Module):
     collected = ["LICENSE"]
 
     for node in tree.body:
         if isinstance(node, ast.FunctionDef):
             for dec in node.decorator_list:
                 if (
-                    isinstance(dec, ast.Call)
-                    and isinstance(dec.func, ast.Name)
-                    and dec.func.id == "section"
-                    and len(dec.args) == 1
-                    and isinstance(dec.args[0], ast.Constant)
-                    and isinstance(dec.args[0].value, str)
+                        isinstance(dec, ast.Call)
+                        and isinstance(dec.func, ast.Name)
+                        and dec.func.id == "section"
+                        and len(dec.args) == 1
+                        and isinstance(dec.args[0], ast.Constant)
+                        and isinstance(dec.args[0].value, str)
                 ):
                     collected.append(node.name)
 
-                elif isinstance(dec, ast.Name) and dec.id == "bpfglobal":
-                    collected.append(node.name)
+                # NOTE: all globals other than
+                # elif isinstance(dec, ast.Name) and dec.id == "bpfglobal":
+                #     collected.append(node.name)
 
                 elif isinstance(dec, ast.Name) and dec.id == "map":
                     collected.append(node.name)
 
-    emit_globals(module, collected)
+    emit_llvm_compiler_used(module, collected)

tests/c-form/globals.bpf.c

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <linux/types.h>
+
+struct test_struct {
+    __u64 a;
+    __u64 b;
+};
+
+struct test_struct w = {};
+volatile __u64 prev_time = 0;
+
+SEC("tracepoint/syscalls/sys_enter_execve")
+int trace_execve(void *ctx)
+{
+    bpf_printk("previous %ul now %ul", w.b, w.a);
+    __u64 ts = bpf_ktime_get_ns();
+    bpf_printk("prev %ul now %ul", prev_time, ts);
+    w.a = ts;
+    w.b = prev_time;
+    prev_time = ts;
+    return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";

tests/failing_tests/globals.py

@@ -0,0 +1,23 @@
+import logging
+
+from pythonbpf import compile, bpf, section, bpfglobal, compile_to_ir
+from ctypes import c_void_p, c_int64
+
+@bpf
+@bpfglobal
+def somevalue() -> c_int64:
+    return c_int64(0)
+
+@bpf
+@section("sometag1")
+def sometag(ctx: c_void_p) -> c_int64:
+    return c_int64(0)
+
+@bpf
+@bpfglobal
+def LICENSE() -> str:
+    return "GPL"
+
+
+compile_to_ir("globals.py", "globals.ll", loglevel=logging.INFO)
+compile()