add map update function support

Author: varun-r-mallya

examples/execve3.py

@@ -37,7 +37,7 @@ def hello_again(ctx: c_void_p) -> c_int64:
     if x:
         print("we did not prevail")
     ts = ktime()
-#    last().update(key, ts)
+    last().update(key, ts, 0)
     return c_int64(0)
 
 
@@ -46,5 +46,4 @@ def hello_again(ctx: c_void_p) -> c_int64:
 def LICENSE() -> str:
     return "GPL"
 
-
 compile()

pythonbpf/bpf_helper_handler.py

@@ -19,7 +19,6 @@ def bpf_map_lookup_elem_emitter(call, map_ptr, module, builder, local_sym_tab=No
     """
     Emit LLVM IR for bpf_map_lookup_elem helper function call.
     """
-
     if call.args and len(call.args) != 1:
         raise ValueError("Map lookup expects exactly one argument, got "
                          f"{len(call.args)}")
@@ -94,11 +93,105 @@ def bpf_printk_emitter(call, module, builder, func):
             builder.call(fn_ptr, [fmt_ptr, ir.Constant(
                 ir.IntType(32), len(fmt_str))], tail=True)
 
+def bpf_map_update_elem_emitter(call, map_ptr, module, builder, local_sym_tab=None):
+    """
+    Emit LLVM IR for bpf_map_update_elem helper function call.
+    Expected call signature: map.update(key, value, flags=0)
+    """
+    if not call.args or len(call.args) < 2 or len(call.args) > 3:
+        raise ValueError("Map update expects 2 or 3 arguments (key, value, flags), got "
+                         f"{len(call.args)}")
+    
+    key_arg = call.args[0]
+    value_arg = call.args[1]
+    flags_arg = call.args[2] if len(call.args) > 2 else None
+    
+    # Handle key
+    if isinstance(key_arg, ast.Name):
+        key_name = key_arg.id
+        if local_sym_tab and key_name in local_sym_tab:
+            key_ptr = local_sym_tab[key_name]
+        else:
+            raise ValueError(
+                f"Key variable {key_name} not found in local symbol table.")
+    elif isinstance(key_arg, ast.Constant) and isinstance(key_arg.value, int):
+        # Handle constant integer keys
+        key_val = key_arg.value
+        key_type = ir.IntType(64)
+        key_ptr = builder.alloca(key_type)
+        key_ptr.align = key_type.width // 8
+        builder.store(ir.Constant(key_type, key_val), key_ptr)
+    else:
+        raise NotImplementedError(
+            "Only simple variable names and integer constants are supported as keys in map update.")
+    
+    # Handle value
+    if isinstance(value_arg, ast.Name):
+        value_name = value_arg.id
+        if local_sym_tab and value_name in local_sym_tab:
+            value_ptr = local_sym_tab[value_name]
+        else:
+            raise ValueError(
+                f"Value variable {value_name} not found in local symbol table.")
+    elif isinstance(value_arg, ast.Constant) and isinstance(value_arg.value, int):
+        # Handle constant integers
+        value_val = value_arg.value
+        value_type = ir.IntType(64)
+        value_ptr = builder.alloca(value_type)
+        value_ptr.align = value_type.width // 8
+        builder.store(ir.Constant(value_type, value_val), value_ptr)
+    else:
+        raise NotImplementedError(
+            "Only simple variable names and integer constants are supported as values in map update.")
+    
+    # Handle flags argument (defaults to 0)
+    if flags_arg is not None:
+        if isinstance(flags_arg, ast.Constant) and isinstance(flags_arg.value, int):
+            flags_val = flags_arg.value
+        elif isinstance(flags_arg, ast.Name):
+            flags_name = flags_arg.id
+            if local_sym_tab and flags_name in local_sym_tab:
+                # Assume it's a stored integer value, load it
+                flags_ptr = local_sym_tab[flags_name]
+                flags_val = builder.load(flags_ptr)
+            else:
+                raise ValueError(
+                    f"Flags variable {flags_name} not found in local symbol table.")
+        else:
+            raise NotImplementedError(
+                "Only integer constants and simple variable names are supported as flags in map update.")
+    else:
+        flags_val = 0
+    
+    if key_ptr is None or value_ptr is None:
+        raise ValueError("Key pointer or value pointer is None.")
+
+    map_void_ptr = builder.bitcast(map_ptr, ir.PointerType())
+    fn_type = ir.FunctionType(
+        ir.IntType(64),
+        [ir.PointerType(), ir.PointerType(), ir.PointerType(), ir.IntType(64)],
+        var_arg=False
+    )
+    fn_ptr_type = ir.PointerType(fn_type)
+    
+    # helper id
+    fn_addr = ir.Constant(ir.IntType(64), 2)
+    fn_ptr = builder.inttoptr(fn_addr, fn_ptr_type)
+    
+    if isinstance(flags_val, int):
+        flags_const = ir.Constant(ir.IntType(64), flags_val)
+    else:
+        flags_const = flags_val
+
+    result = builder.call(fn_ptr, [map_void_ptr, key_ptr, value_ptr, flags_const], tail=False)
+    
+    return result
 
 helper_func_list = {
     "lookup": bpf_map_lookup_elem_emitter,
     "print": bpf_printk_emitter,
     "ktime": bpf_ktime_get_ns_emitter,
+    "update": bpf_map_update_elem_emitter,
 }
 
 

pythonbpf/functions_pass.py

@@ -106,6 +106,18 @@ def handle_expr(func, module, builder, expr, local_sym_tab, map_sym_tab):
                 handle_helper_call(
                     call, module, builder, func, local_sym_tab, map_sym_tab)
                 return
+        elif isinstance(call.func, ast.Attribute):
+            if isinstance(call.func.value, ast.Call) and isinstance(call.func.value.func, ast.Name):
+                method_name = call.func.attr
+                if method_name in helper_func_list:
+                    handle_helper_call(
+                        call, module, builder, func, local_sym_tab, map_sym_tab)
+                    return
+            # I VIBED THIS WITHOUT UNDERSTANDING THIS PART>>>> TODO: check this later
+            if call.func.id in helper_func_list:
+                handle_helper_call(
+                    call, module, builder, func, local_sym_tab, map_sym_tab)
+                return
     elif isinstance(call, ast.Name):
         if call.id in local_sym_tab:
             var = local_sym_tab[call.id]

pythonbpf/maps.py

@@ -16,8 +16,9 @@ def delete(self, key):
             del self.entries[key]
         else:
             raise KeyError(f"Key {key} not found in map")
-            
-    def update(self, key, value):
+    
+    # TODO: define the flags that can be added
+    def update(self, key, value, flags=None):
         if key in self.entries:
             self.entries[key] = value
         else: