Implement BPF_PROBE_READ helper

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 @@ __all__ = [
     "deref",
     "comm",
     "probe_read_str",
+    "random",
     "XDP_DROP",
     "XDP_PASS",
 ]

pythonbpf/helper/bpf_helper_handler.py

@@ -10,6 +10,7 @@ from .helper_utils import (
     get_buffer_ptr_and_size,
     get_char_array_ptr_and_size,
     get_ptr_from_arg,
+    get_int_value_from_arg,
 )
 from .printk_formatter import simple_string_print, handle_fstring_print
 
@@ -23,8 +24,10 @@ class BPFHelperID(Enum):
     BPF_MAP_LOOKUP_ELEM = 1
     BPF_MAP_UPDATE_ELEM = 2
     BPF_MAP_DELETE_ELEM = 3
+    BPF_PROBE_READ = 4
     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 +436,86 @@ 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)
+
+
+@HelperHandlerRegistry.register("probe_read")
+def bpf_probe_read_emitter(
+    call,
+    map_ptr,
+    module,
+    builder,
+    func,
+    local_sym_tab=None,
+    struct_sym_tab=None,
+    map_sym_tab=None,
+):
+    """
+    Emit LLVM IR for bpf_probe_read helper function
+    """
+
+    if len(call.args) != 3:
+        logger.warn("Expected 3 args for probe_read helper")
+        return
+    dst_ptr, _ = get_ptr_from_arg(
+        call.args[0], func, module, builder, local_sym_tab, map_sym_tab, struct_sym_tab
+    )
+    size_val = (
+        get_int_value_from_arg(
+            call.args[1],
+            func,
+            module,
+            builder,
+            local_sym_tab,
+            map_sym_tab,
+            struct_sym_tab,
+        )
+        & 0xFFFFFFFF
+    )
+    src_ptr, _ = get_ptr_from_arg(
+        call.args[2], func, module, builder, local_sym_tab, map_sym_tab, struct_sym_tab
+    )
+    fn_type = ir.FunctionType(
+        ir.IntType(64),
+        [ir.PointerType(), ir.IntType(32), ir.PointerType()],
+        var_arg=False,
+    )
+    fn_ptr = builder.inttoptr(
+        ir.Constant(ir.IntType(64), BPFHelperID.BPF_PROBE_READ.value),
+        ir.PointerType(fn_type),
+    )
+    result = builder.call(
+        fn_ptr,
+        [
+            builder.bitcast(dst_ptr, ir.PointerType()),
+            ir.Constant(ir.IntType(32), size_val),
+            builder.bitcast(src_ptr, ir.PointerType()),
+        ],
+        tail=False,
+    )
+    logger.info(f"Emitted bpf_probe_read (size={size_val})")
+    return result, ir.IntType(64)
+
+
 def handle_helper_call(
     call,
     module,

pythonbpf/helper/helper_utils.py

@@ -274,3 +274,23 @@ def get_ptr_from_arg(
         raise ValueError(f"Expected pointer type, got {val_type}")
 
     return val, val_type
+
+
+def get_int_value_from_arg(
+    arg, func, module, builder, local_sym_tab, map_sym_tab, struct_sym_tab
+):
+    """Evaluate argument and return integer value"""
+
+    result = eval_expr(
+        func, module, builder, arg, local_sym_tab, map_sym_tab, struct_sym_tab
+    )
+
+    if not result:
+        raise ValueError("Failed to evaluate argument")
+
+    val, val_type = result
+
+    if not isinstance(val_type, ir.IntType):
+        raise ValueError(f"Expected integer type, got {val_type}")
+
+    return val

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)

tests/passing_tests/helpers/prandom.py

@@ -0,0 +1,25 @@
+from pythonbpf import bpf, bpfglobal, section, BPF, trace_pipe
+from ctypes import c_void_p, c_int64
+from pythonbpf.helper import random
+
+
+@bpf
+@section("tracepoint/syscalls/sys_enter_clone")
+def hello_world(ctx: c_void_p) -> c_int64:
+    r = random()
+    print(f"Hello, World!, {r}")
+    return 0  # type: ignore [return-value]
+
+
+@bpf
+@bpfglobal
+def LICENSE() -> str:
+    return "GPL"
+
+
+# Compile and load
+b = BPF()
+b.load()
+b.attach_all()
+
+trace_pipe()