add i32 support special case and find ctx repetition in multiple functions error.

Author: varun-r-mallya

pythonbpf/allocation_pass.py

@@ -81,7 +81,7 @@ def _allocate_for_call(builder, var_name, rval, local_sym_tab, structs_sym_tab):
         call_type = rval.func.id
 
         # C type constructors
-        if call_type in ("c_int32", "c_int64", "c_uint32", "c_uint64"):
+        if call_type in ("c_int32", "c_int64", "c_uint32", "c_uint64", "c_void_p"):
             ir_type = ctypes_to_ir(call_type)
             var = builder.alloca(ir_type, name=var_name)
             var.align = ir_type.width // 8
@@ -259,7 +259,16 @@ def _allocate_for_attribute(builder, var_name, rval, local_sym_tab, structs_sym_
                     field_size_bits = field_size_bytes * 8
 
                     if field_size_bits in [8, 16, 32, 64]:
-                        actual_ir_type = ir.IntType(field_size_bits)
+                        # Special case: struct_xdp_md i32 fields should allocate as i64
+                        # because load_ctx_field will zero-extend them to i64
+                        if vmlinux_struct_name == "struct_xdp_md" and field_size_bits == 32:
+                            actual_ir_type = ir.IntType(64)
+                            logger.info(
+                                f"Allocating {var_name} as i64 for i32 field from struct_xdp_md.{field_name} "
+                                "(will be zero-extended during load)"
+                            )
+                        else:
+                            actual_ir_type = ir.IntType(field_size_bits)
                     else:
                         logger.warning(
                             f"Unusual field size {field_size_bits} bits for {field_name}"

pythonbpf/assign_pass.py

@@ -152,15 +152,26 @@ def handle_variable_assignment(
     if val_type != var_type:
         if isinstance(val_type, Field):
             logger.info("Handling assignment to struct field")
+            # Special handling for struct_xdp_md i32 fields that are zero-extended to i64
+            # The load_ctx_field already extended them, so val is i64 but val_type.type shows c_uint
+            if (hasattr(val_type, 'type') and
+                val_type.type.__name__ == "c_uint" and
+                isinstance(var_type, ir.IntType) and
+                var_type.width == 64):
+                # This is the struct_xdp_md case - value is already i64
+                builder.store(val, var_ptr)
+                logger.info(f"Assigned zero-extended struct_xdp_md i32 field to {var_name} (i64)")
+                return True
             # TODO: handling only ctype struct fields for now. Handle other stuff too later.
-            if var_type == ctypes_to_ir(val_type.type.__name__):
+            elif var_type == ctypes_to_ir(val_type.type.__name__):
                 builder.store(val, var_ptr)
                 logger.info(f"Assigned ctype struct field to {var_name}")
                 return True
-            logger.error(
-                f"Failed to assign ctype struct field to {var_name}: {val_type} != {var_type}"
-            )
-            return False
+            else:
+                logger.error(
+                    f"Failed to assign ctype struct field to {var_name}: {val_type} != {var_type}"
+                )
+                return False
         elif isinstance(val_type, ir.IntType) and isinstance(var_type, ir.IntType):
             # Allow implicit int widening
             if val_type.width < var_type.width:

pythonbpf/vmlinux_parser/vmlinux_exports_handler.py

@@ -94,20 +94,21 @@ def handle_vmlinux_struct_field(
                 f"Attempting to access field {field_name} of possible vmlinux struct {struct_var_name}"
             )
             python_type: type = var_info.metadata
+            struct_name = python_type.__name__
             globvar_ir, field_data = self.get_field_type(
-                python_type.__name__, field_name
+                struct_name, field_name
             )
             builder.function.args[0].type = ir.PointerType(ir.IntType(8))
             field_ptr = self.load_ctx_field(
-                builder, builder.function.args[0], globvar_ir, field_data
+                builder, builder.function.args[0], globvar_ir, field_data, struct_name
             )
             # Return pointer to field and field type
             return field_ptr, field_data
         else:
             raise RuntimeError("Variable accessed not found in symbol table")
 
     @staticmethod
-    def load_ctx_field(builder, ctx_arg, offset_global, field_data):
+    def load_ctx_field(builder, ctx_arg, offset_global, field_data, struct_name=None):
         """
         Generate LLVM IR to load a field from BPF context using offset.
 
@@ -116,8 +117,9 @@ def load_ctx_field(builder, ctx_arg, offset_global, field_data):
             ctx_arg: The context pointer argument (ptr/i8*)
             offset_global: Global variable containing the field offset (i64)
             field_data: contains data about the field
+            struct_name: Name of the struct being accessed (optional)
         Returns:
-            The loaded value (i64 register)
+            The loaded value (i64 register or appropriately sized)
         """
 
         # Load the offset value
@@ -164,6 +166,7 @@ def load_ctx_field(builder, ctx_arg, offset_global, field_data):
 
         # Determine the appropriate IR type based on field information
         int_width = 64  # Default to 64-bit
+        needs_zext = False  # Track if we need zero-extension for xdp_md
 
         if field_data is not None:
             # Try to determine the size from field metadata
@@ -175,6 +178,12 @@ def load_ctx_field(builder, ctx_arg, offset_global, field_data):
                     if field_size_bits in [8, 16, 32, 64]:
                         int_width = field_size_bits
                         logger.info(f"Determined field size: {int_width} bits")
+
+                        # Special handling for struct_xdp_md i32 fields
+                        # Load as i32 but extend to i64 before storing
+                        if struct_name == "struct_xdp_md" and int_width == 32:
+                            needs_zext = True
+                            logger.info(f"struct_xdp_md i32 field detected, will zero-extend to i64")
                     else:
                         logger.warning(
                             f"Unusual field size {field_size_bits} bits, using default 64"
@@ -203,6 +212,11 @@ def load_ctx_field(builder, ctx_arg, offset_global, field_data):
         # Load and return the value
         value = builder.load(typed_ptr)
 
+        # Zero-extend i32 to i64 for struct_xdp_md fields
+        if needs_zext:
+            value = builder.zext(value, ir.IntType(64))
+            logger.info("Zero-extended i32 value to i64 for struct_xdp_md field")
+
         return value
 
     def has_field(self, struct_name, field_name):

tests/c-form/Makefile

@@ -1,19 +1,23 @@
 BPF_CLANG := clang
-CFLAGS := -O0 -emit-llvm -target bpf -c
+CFLAGS := -emit-llvm -target bpf -c
 
 SRC := $(wildcard *.bpf.c)
 LL := $(SRC:.bpf.c=.bpf.ll)
+LL2 := $(SRC:.bpf.c=.bpf.o2.ll)
 OBJ := $(SRC:.bpf.c=.bpf.o)
 
 .PHONY: all clean
 
-all: $(LL) $(OBJ)
+all: $(LL) $(OBJ) $(LL2)
 
 %.bpf.o: %.bpf.c
 	$(BPF_CLANG) -O2 -g -target bpf -c $< -o $@
 
 %.bpf.ll: %.bpf.c
-	$(BPF_CLANG) $(CFLAGS) -g -S $< -o $@
+	$(BPF_CLANG) -O0 $(CFLAGS) -g -S $< -o $@
+
+%.bpf.o2.ll: %.bpf.c
+	$(BPF_CLANG) -O2 $(CFLAGS) -g -S $< -o $@
 
 clean:
-	rm -f $(LL) $(OBJ)
+	rm -f $(LL) $(OBJ) $(LL2)

tests/c-form/i32test.bpf.c

@@ -5,9 +5,9 @@ SEC("xdp")
 int print_xdp_data(struct xdp_md *ctx)
 {
     // 'data' is a pointer to the start of packet data
-    void *data = (void *)(long)ctx->data;
+    long data = (long)ctx->data;
 
-    bpf_printk("ctx->data = %p\n", data);
+    bpf_printk("ctx->data = %lld\n", data);
 
     return XDP_PASS;
 }

tests/failing_tests/vmlinux/i32_test.py

@@ -1,4 +1,4 @@
-from ctypes import c_int64, c_int32
+from ctypes import c_int64, c_int32, c_void_p
 from pythonbpf import bpf, section, bpfglobal, compile_to_ir, compile
 from vmlinux import struct_xdp_md
 from vmlinux import XDP_PASS
@@ -8,10 +8,16 @@
 @section("xdp")
 def print_xdp_data(ctx: struct_xdp_md) -> c_int64:
     data = ctx.data  # 32-bit field: packet start pointer
-    something = c_int32(2 + data)
+    something = c_void_p(data)
     print(f"ctx->data = {something}")
     return c_int64(XDP_PASS)
 
+@bpf
+@section("xdp")
+def print_xdp_dat2a(ct2x: struct_xdp_md) -> c_int64:
+    data = ct2x.data  # 32-bit field: packet start pointer
+    print(f"ct2x->data = {data}")
+    return c_int64(XDP_PASS)
 
 @bpf
 @bpfglobal