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implement bpf map lookup emission

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This commit is contained in:
Pragyansh Chaturvedi
2025-09-09 01:04:17 +05:30
parent 414db121b3
commit ff7663803d
2 changed files with 33 additions and 4 deletions
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26
pythonbpf/bpf_helper_handler.py
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@ -6,6 +6,32 @@ def bpf_ktime_get_ns_emitter(call, module, builder, func):
pass
def bpf_map_lookup_elem_emitter(map_ptr, key_ptr, module, builder):
"""
Emit LLVM IR for bpf_map_lookup_elem helper function call.
"""
# Cast pointers to void*
map_void_ptr = builder.bitcast(map_ptr, ir.PointerType())
# Define function type for bpf_map_lookup_elem
# The function takes two void* arguments and returns void*
fn_type = ir.FunctionType(
ir.PointerType(), # Return type: void*
[ir.PointerType(), ir.PointerType()], # Args: (void*, void*)
var_arg=False
)
fn_ptr_type = ir.PointerType(fn_type)
# Helper ID 1 is bpf_map_lookup_elem
fn_addr = ir.Constant(ir.IntType(64), 1)
fn_ptr = builder.inttoptr(fn_addr, fn_ptr_type)
# Call the helper function
result = builder.call(fn_ptr, [map_void_ptr, key_ptr], tail=False)
return result
def bpf_printk_emitter(call, module, builder, func):
if not hasattr(func, "_fmt_counter"):
func._fmt_counter = 0

11
pythonbpf/functions_pass.py
View File

@ -1,7 +1,7 @@
from llvmlite import ir
import ast
from .bpf_helper_handler import bpf_printk_emitter, bpf_ktime_get_ns_emitter
from .bpf_helper_handler import bpf_printk_emitter, bpf_ktime_get_ns_emitter, bpf_map_lookup_elem_emitter
from .type_deducer import ctypes_to_ir
@ -79,28 +79,31 @@ def handle_assign(module, builder, stmt, map_sym_tab, local_sym_tab):
key_type = ir.IntType(64)
print(f"Key type: {key_type}")
print(f"Key val: {key_val}")
key_var = builder.alloca(key_type)
key_var.align = key_type // 8
builder.store(ir.Constant(
key_type, key_val), key_var)
elif isinstance(key_arg, ast.Name):
# Check in local symtab first
if key_arg.id in local_sym_tab:
key_var = local_sym_tab[key_arg.id]
key_type = key_var.type.pointee
key_val = builder.load(key_var)
elif key_arg.id in map_sym_tab:
key_var = map_sym_tab[key_arg.id]
key_type = key_var.type.pointee
key_val = builder.load(key_var)
else:
print("Key variable "
f"{key_arg.id} not found in symtabs")
return
print(f"Found key variable {key_arg.id} in symtab")
print(f"Key type: {key_type}")
print(f"Key val: {key_val}")
else:
print("Unsupported lookup key arg")
return
# TODO: generate call to bpf_map_lookup_elem
result_ptr = bpf_map_lookup_elem_emitter(
map_global, key_var, module, builder)
else:
print(f"Map {map_name} not found in symbol table")