generate IR partly

pythonbpf/allocation_pass.py

@@ -245,13 +245,17 @@ def _allocate_for_attribute(builder, var_name, rval, local_sym_tab, structs_sym_
 
             # loaded_value = builder.load(field_ir, align=8)
             # #TODO: fatal flaw that this always assumes first argument of function to be the context of what this gets.
-            # base_ptr = builder.function.args[0]
+            base_ptr = builder.function.args[0]
+            local_sym_tab[
+                struct_var
+            ].var = base_ptr  # This is repurposing of var to store the pointer of the base type
+            local_sym_tab[struct_var].ir_type = field_ir
             # gep_result = builder.gep(
             #     base_ptr,
             #     [loaded_value],
             #     inbounds=False,  # Not using inbounds GEP
             # )
-            # print("DEBB", loaded_value, base_ptr, gep_result)
+            # print("DEBUG", loaded_value, base_ptr, gep_result)
             # Use i64 for allocation since that's what the global variable contains
 
             actual_ir_type = ir.IntType(64)

pythonbpf/vmlinux_parser/vmlinux_exports_handler.py

@@ -97,7 +97,16 @@ class VmlinuxHandler:
             globvar_ir, field_data = self.get_field_type(
                 python_type.__name__, field_name
             )
-
+            # field_index = self.get_field_index(python_type.__name__, field_name)
+            offset = builder.load(globvar_ir)
+            i8_ptr_type = ir.IntType(8).as_pointer()
+            byte_ptr = builder.bitcast(var_info.var, i8_ptr_type)
+            print(byte_ptr)
+            # Step 3: GEP with the offset to get field pointer
+            field_ptr_i8 = builder.gep(
+                byte_ptr, [ir.Constant(ir.IntType(32), 0), offset], inbounds=False
+            )
+            print(field_ptr_i8)
             # Return pointer to field and field type
             return None
         else:
@@ -122,3 +131,18 @@ class VmlinuxHandler:
                 )
         else:
             raise ValueError(f"{vmlinux_struct_name} is not a vmlinux struct")
+
+    def get_field_index(self, vmlinux_struct_name, field_name):
+        """Get the type of a field in a vmlinux struct"""
+        if self.is_vmlinux_struct(vmlinux_struct_name):
+            python_type = self.vmlinux_symtab[vmlinux_struct_name]["python_type"]
+            if hasattr(python_type, field_name):
+                return list(
+                    self.vmlinux_symtab[vmlinux_struct_name]["members"].keys()
+                ).index(field_name)
+            else:
+                raise ValueError(
+                    f"Field {field_name} not found in vmlinux struct {vmlinux_struct_name}"
+                )
+        else:
+            raise ValueError(f"{vmlinux_struct_name} is not a vmlinux struct")

tests/c-form/struct_field_tests.bpf.c

@@ -21,7 +21,21 @@ int handle_setuid_entry(struct trace_event_raw_sys_enter *ctx) {
   // Access each argument separately with clear variable assignments
   long int arg0 = ctx->id;
   bpf_printk("args[0]: %d", arg0);
-
+  /*
+   * the IR to aim for is
+   * %2 = alloca ptr, align 8
+   * store ptr %0, ptr %2, align 8
+   * Above, %0 is the arg pointer
+   * %5 = load ptr, ptr %2, align 8
+   * %6 = getelementptr inbounds %struct.trace_event_raw_sys_enter, ptr %5, i32 0, i32 2
+   * %7 = load i64, ptr @"llvm.trace_event_raw_sys_enter:0:16$0:2:0", align 8
+   * %8 = bitcast ptr %5 to ptr
+   * %9 = getelementptr i8, ptr %8, i64 %7
+   * %10 = bitcast ptr %9 to ptr
+   * %11 = call ptr @llvm.bpf.passthrough.p0.p0(i32 0, ptr %10)
+   * %12 = load i64, ptr %11, align 8, !dbg !101
+   *
+   */
   return 0;
 }