Add bpf_get_prandom_u32 helper

Author: r41k0u

pythonbpf/helper/__init__.py

@@ -1,7 +1,7 @@
 from .helper_registry import HelperHandlerRegistry
 from .helper_utils import reset_scratch_pool
 from .bpf_helper_handler import handle_helper_call, emit_probe_read_kernel_str_call
-from .helpers import ktime, pid, deref, comm, probe_read_str, XDP_DROP, XDP_PASS
+from .helpers import ktime, pid, deref, comm, probe_read_str, random, XDP_DROP, XDP_PASS
 
 
 # Register the helper handler with expr module
@@ -65,6 +65,7 @@ def helper_call_handler(
     "deref",
     "comm",
     "probe_read_str",
+    "random",
     "XDP_DROP",
     "XDP_PASS",
 ]

pythonbpf/helper/bpf_helper_handler.py

@@ -25,6 +25,7 @@ class BPFHelperID(Enum):
     BPF_MAP_DELETE_ELEM = 3
     BPF_KTIME_GET_NS = 5
     BPF_PRINTK = 6
+    BPF_GET_PRANDOM_U32 = 7
     BPF_GET_CURRENT_PID_TGID = 14
     BPF_GET_CURRENT_COMM = 16
     BPF_PERF_EVENT_OUTPUT = 25
@@ -433,6 +434,28 @@ def bpf_probe_read_kernel_str_emitter(
     return result, ir.IntType(64)
 
 
+@HelperHandlerRegistry.register("random")
+def bpf_get_prandom_u32_emitter(
+    call,
+    map_ptr,
+    module,
+    builder,
+    func,
+    local_sym_tab=None,
+    struct_sym_tab=None,
+    map_sym_tab=None,
+):
+    """
+    Emit LLVM IR for bpf_get_prandom_u32 helper function call.
+    """
+    helper_id = ir.Constant(ir.IntType(64), BPFHelperID.BPF_GET_PRANDOM_U32.value)
+    fn_type = ir.FunctionType(ir.IntType(32), [], var_arg=False)
+    fn_ptr_type = ir.PointerType(fn_type)
+    fn_ptr = builder.inttoptr(helper_id, fn_ptr_type)
+    result = builder.call(fn_ptr, [], tail=False)
+    return result, ir.IntType(32)
+
+
 def handle_helper_call(
     call,
     module,

pythonbpf/helper/helpers.py

@@ -27,6 +27,11 @@ def probe_read_str(dst, src):
     return ctypes.c_int64(0)
 
 
+def random():
+    """get a pseudorandom u32 number"""
+    return ctypes.c_int32(0)
+
+
 XDP_ABORTED = ctypes.c_int64(0)
 XDP_DROP = ctypes.c_int64(1)
 XDP_PASS = ctypes.c_int64(2)