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Complete struct field assignment

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This commit is contained in:
Pragyansh Chaturvedi
2025-09-21 05:22:00 +05:30
parent 36c2c0b695
commit 0f9a4078ee
3 changed files with 72 additions and 11 deletions
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4
examples/c-form/ex6.bpf.c
View File

@ -9,7 +9,7 @@
struct data_t {
__u32 pid;
__u64 ts;
char comm[TASK_COMM_LEN];
// char comm[TASK_COMM_LEN];
};
// Define a perf event output map
@ -31,7 +31,7 @@ int hello(struct pt_regs *ctx)
data.ts = bpf_ktime_get_ns();
// Get current process name
bpf_get_current_comm(&data.comm, sizeof(data.comm));
// bpf_get_current_comm(&data.comm, sizeof(data.comm));
// Submit data to userspace via perf event
bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU,

4
examples/execve5.py
View File

@ -11,17 +11,21 @@ class data_t:
pid: c_uint64
ts: c_uint64
@bpf
@map
def events() -> PerfEventArray:
return PerfEventArray(key_size=c_int32, value_size=c_int32)
@bpf
@section("tracepoint/syscalls/sys_enter_clone")
def hello(ctx: c_void_p) -> c_int32:
dataobj = data_t()
ts = ktime()
process_id = pid()
dataobj.pid = process_id
dataobj.ts = ts
print(f"clone called at {ts} by pid {process_id}")
return c_int32(0)

75
pythonbpf/functions_pass.py
View File

@ -27,7 +27,7 @@ def get_probe_string(func_node):
return "helper"
def handle_assign(func, module, builder, stmt, map_sym_tab, local_sym_tab):
def handle_assign(func, module, builder, stmt, map_sym_tab, local_sym_tab, structs_sym_tab):
"""Handle assignment statements in the function body."""
if len(stmt.targets) != 1:
print("Unsupported multiassignment")
@ -36,12 +36,35 @@ def handle_assign(func, module, builder, stmt, map_sym_tab, local_sym_tab):
num_types = ("c_int32", "c_int64", "c_uint32", "c_uint64")
target = stmt.targets[0]
if not isinstance(target, ast.Name):
print(f"Handling assignment to {ast.dump(target)}")
if not isinstance(target, ast.Name) and not isinstance(target, ast.Attribute):
print("Unsupported assignment target")
return
var_name = target.id
var_name = target.id if isinstance(target, ast.Name) else target.value.id
rval = stmt.value
if isinstance(rval, ast.Constant):
if isinstance(target, ast.Attribute):
# struct field assignment
field_name = target.attr
if var_name in local_sym_tab and var_name in local_var_metadata:
struct_type = local_var_metadata[var_name]
struct_info = structs_sym_tab[struct_type]
if field_name in struct_info["fields"]:
field_idx = struct_info["fields"][field_name]
struct_ptr = local_sym_tab[var_name]
field_ptr = builder.gep(
struct_ptr, [ir.Constant(ir.IntType(32), 0),
ir.Constant(ir.IntType(32), field_idx)],
inbounds=True)
val = eval_expr(func, module, builder, rval,
local_sym_tab, map_sym_tab)
if val is None:
print("Failed to evaluate struct field assignment")
return
builder.store(val, field_ptr)
print(f"Assigned to struct field {var_name}.{field_name}")
return
elif isinstance(rval, ast.Constant):
if isinstance(rval.value, bool):
if rval.value:
builder.store(ir.Constant(ir.IntType(1), 1),
@ -92,10 +115,46 @@ def handle_assign(func, module, builder, stmt, map_sym_tab, local_sym_tab):
builder.store(val, local_sym_tab[var_name])
# local_sym_tab[var_name] = var
print(f"Dereferenced and assigned to {var_name}")
elif call_type in structs_sym_tab and len(rval.args) == 0:
struct_info = structs_sym_tab[call_type]
ir_type = struct_info["type"]
# var = builder.alloca(ir_type, name=var_name)
# Null init
builder.store(ir.Constant(ir_type, None),
local_sym_tab[var_name])
local_var_metadata[var_name] = call_type
print(f"Assigned struct {call_type} to {var_name}")
# local_sym_tab[var_name] = var
else:
print(f"Unsupported assignment call type: {call_type}")
elif isinstance(rval.func, ast.Attribute):
if isinstance(rval.func.value, ast.Call) and isinstance(rval.func.value.func, ast.Name):
print(f"Assignment call attribute: {ast.dump(rval.func)}")
if isinstance(rval.func.value, ast.Name):
# probably a struct access
var_name = rval.func.value.id
field_name = rval.func.attr
print(f"Handling struct field assignment"
f"{var_name}.{field_name}")
if var_name in local_sym_tab and var_name in local_var_metadata:
struct_type = local_var_metadata[var_name]
struct_info = structs_sym_tab[struct_type]
if field_name in struct_info["fields"]:
field_idx = struct_info["fields"][field_name]
struct_ptr = local_sym_tab[var_name]
field_ptr = builder.gep(
struct_ptr, [ir.Constant(ir.IntType(32), 0),
ir.Constant(ir.IntType(32), field_idx)],
inbounds=True)
val = eval_expr(func, module, builder, rval,
local_sym_tab, map_sym_tab)
if val is None:
print("Failed to evaluate struct field assignment")
return
builder.store(val, field_ptr)
elif isinstance(rval.func.value, ast.Call) and isinstance(rval.func.value.func, ast.Name):
map_name = rval.func.value.func.id
method_name = rval.func.attr
if map_name in map_sym_tab:
@ -226,7 +285,8 @@ def process_stmt(func, module, builder, stmt, local_sym_tab, map_sym_tab, struct
if isinstance(stmt, ast.Expr):
handle_expr(func, module, builder, stmt, local_sym_tab, map_sym_tab)
elif isinstance(stmt, ast.Assign):
handle_assign(func, module, builder, stmt, map_sym_tab, local_sym_tab)
handle_assign(func, module, builder, stmt, map_sym_tab,
local_sym_tab, structs_sym_tab)
elif isinstance(stmt, ast.AugAssign):
raise SyntaxError("Augmented assignment not supported")
elif isinstance(stmt, ast.If):
@ -304,9 +364,6 @@ def allocate_mem(module, builder, body, func, ret_type, map_sym_tab, local_sym_t
struct_info = structs_sym_tab[call_type]
ir_type = struct_info["type"]
var = builder.alloca(ir_type, name=var_name)
# Null init
builder.store(ir.Constant(ir_type, None), var)
local_var_metadata[var_name] = call_type
print(
f"Pre-allocated variable {var_name} for struct {call_type}")