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Use pointer arithmetic to resolve vmlinux struct fields

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This commit is contained in:
Pragyansh Chaturvedi
2025-10-25 05:40:45 +05:30
parent 96216d4411
commit 1ea44dd8e1
1 changed files with 15 additions and 9 deletions
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24
pythonbpf/vmlinux_parser/vmlinux_exports_handler.py
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@ -97,18 +97,24 @@ class VmlinuxHandler:
globvar_ir, field_data = self.get_field_type( globvar_ir, field_data = self.get_field_type(
python_type.__name__, field_name python_type.__name__, field_name
) )
# field_index = self.get_field_index(python_type.__name__, field_name)
# Load the offset value
offset = builder.load(globvar_ir) offset = builder.load(globvar_ir)
# Convert pointer to integer
i64_type = ir.IntType(64)
ptr_as_int = builder.ptrtoint(var_info.var, i64_type)
# Add the offset
field_addr = builder.add(ptr_as_int, offset)
# Convert back to pointer
i8_ptr_type = ir.IntType(8).as_pointer() i8_ptr_type = ir.IntType(8).as_pointer()
byte_ptr = builder.bitcast(var_info.var, i8_ptr_type) field_ptr_i8 = builder.inttoptr(field_addr, i8_ptr_type)
print(byte_ptr) logger.info(f"field_ptr_i8: {field_ptr_i8}")
# Step 3: GEP with the offset to get field pointer
field_ptr_i8 = builder.gep(
byte_ptr, [ir.Constant(ir.IntType(32), 0), offset], inbounds=False
)
print(field_ptr_i8)
# Return pointer to field and field type # Return pointer to field and field type
return None return field_ptr_i8, field_data
else: else:
raise RuntimeError("Variable accessed not found in symbol table") raise RuntimeError("Variable accessed not found in symbol table")