varun-r-mallya/python-bpf
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separate out bpf_printk IR generator

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varun-r-mallya
2025-09-07 20:22:29 +05:30
parent 1118e4fcd6
commit d52b9ceb69
2 changed files with 36 additions and 29 deletions
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33
pythonbpf/bpf_helper_handler.py Normal file
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@ -0,0 +1,33 @@
import ast
from llvmlite import ir
def bpf_printk_emitter(call, module, builder, func):
# Handle print statement
for arg in call.args:
if isinstance(arg, ast.Constant) and isinstance(arg.value, str):
fmt_str = arg.value + "\n" + "\0"
# Create a global variable for the format string
fmt_gvar = ir.GlobalVariable(
module, ir.ArrayType(ir.IntType(8), len(fmt_str)), name=f"{func.name}____fmt")
fmt_gvar.global_constant = True
fmt_gvar.initializer = ir.Constant( # type: ignore
ir.ArrayType(ir.IntType(8), len(fmt_str)),
bytearray(fmt_str.encode("utf8"))
)
fmt_gvar.linkage = "internal"
fmt_gvar.align = 1 # type: ignore
# Cast the global variable to i8*
fmt_ptr = builder.bitcast(
fmt_gvar, ir.PointerType())
# Call bpf_trace_printk (assumed to be at address 6)
fn_type = ir.FunctionType(ir.IntType(
64), [ir.PointerType(), ir.IntType(32)], var_arg=True)
fn_ptr_type = ir.PointerType(fn_type)
fn_addr = ir.Constant(ir.IntType(64), 6)
fn_ptr = builder.inttoptr(fn_addr, fn_ptr_type)
# Call the function
builder.call(fn_ptr, [fmt_ptr, ir.Constant(
ir.IntType(32), len(fmt_str))], tail=True)

32
pythonbpf/functions_pass.py
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@ -1,5 +1,7 @@
from llvmlite import ir
import ast
from .bpf_helper_handler import bpf_printk_emitter
from .type_deducer import ctypes_to_ir
def get_probe_string(func_node):
@ -26,35 +28,7 @@ def process_func_body(module, builder, func_node, func, ret_type):
if isinstance(stmt, ast.Expr) and isinstance(stmt.value, ast.Call):
call = stmt.value
if isinstance(call.func, ast.Name) and call.func.id == "print":
# Handle print statement
for arg in call.args:
if isinstance(arg, ast.Constant) and isinstance(arg.value, str):
fmt_str = arg.value + "\n" + "\0"
# Create a global variable for the format string
fmt_gvar = ir.GlobalVariable(
module, ir.ArrayType(ir.IntType(8), len(fmt_str)), name=f"{func.name}____fmt")
fmt_gvar.global_constant = True
fmt_gvar.initializer = ir.Constant( # type: ignore
ir.ArrayType(ir.IntType(8), len(fmt_str)),
bytearray(fmt_str.encode("utf8"))
)
fmt_gvar.linkage = "internal"
fmt_gvar.align = 1 # type: ignore
# Cast the global variable to i8*
fmt_ptr = builder.bitcast(
fmt_gvar, ir.PointerType())
# Call bpf_trace_printk (assumed to be at address 6)
fn_type = ir.FunctionType(ir.IntType(
64), [ir.PointerType(), ir.IntType(32)], var_arg=True)
fn_ptr_type = ir.PointerType(fn_type)
fn_addr = ir.Constant(ir.IntType(64), 6)
fn_ptr = builder.inttoptr(fn_addr, fn_ptr_type)
# Call the function
builder.call(fn_ptr, [fmt_ptr, ir.Constant(
ir.IntType(32), len(fmt_str))], tail=True)
bpf_printk_emitter(call, module, builder, func)
elif isinstance(stmt, ast.Return):
if stmt.value is None:
builder.ret(ir.Constant(ir.IntType(32), 0))