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Extend RemoteUnwinder to capture precise bytecode locations

Browse source 
Introduces LocationInfo struct sequence with end_lineno, col_offset, and
end_col_offset fields. Adds opcodes parameter to RemoteUnwinder that
extracts the currently executing opcode alongside its source span.

Refactors linetable parsing to correctly accumulate line numbers
separately from output values, fixing edge cases in computed_line.
This commit is contained in:
Pablo Galindo Salgado 2025-12-03 03:43:00 +00:00
parent 8801c6dec7
commit dd27e5e679
5 changed files with 146 additions and 46 deletions
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99
Modules/_remote_debugging/code_objects.c
View file

@ -155,48 +155,45 @@ parse_linetable(const uintptr_t addrq, const char* linetable, int firstlineno, L
{
const uint8_t* ptr = (const uint8_t*)(linetable);
uintptr_t addr = 0;
info->lineno = firstlineno;
int computed_line = firstlineno; // Running accumulator, separate from output
while (*ptr != '\0') {
// See InternalDocs/code_objects.md for where these magic numbers are from
// and for the decoding algorithm.
uint8_t first_byte = *(ptr++);
uint8_t code = (first_byte >> 3) & 15;
size_t length = (first_byte & 7) + 1;
uintptr_t end_addr = addr + length;
switch (code) {
case PY_CODE_LOCATION_INFO_NONE: {
case PY_CODE_LOCATION_INFO_NONE:
info->lineno = info->end_lineno = -1;
info->column = info->end_column = -1;
break;
}
case PY_CODE_LOCATION_INFO_LONG: {
int line_delta = scan_signed_varint(&ptr);
info->lineno += line_delta;
info->end_lineno = info->lineno + scan_varint(&ptr);
case PY_CODE_LOCATION_INFO_LONG:
computed_line += scan_signed_varint(&ptr);
info->lineno = computed_line;
info->end_lineno = computed_line + scan_varint(&ptr);
info->column = scan_varint(&ptr) - 1;
info->end_column = scan_varint(&ptr) - 1;
break;
}
case PY_CODE_LOCATION_INFO_NO_COLUMNS: {
int line_delta = scan_signed_varint(&ptr);
info->lineno += line_delta;
case PY_CODE_LOCATION_INFO_NO_COLUMNS:
computed_line += scan_signed_varint(&ptr);
info->lineno = info->end_lineno = computed_line;
info->column = info->end_column = -1;
break;
}
case PY_CODE_LOCATION_INFO_ONE_LINE0:
case PY_CODE_LOCATION_INFO_ONE_LINE1:
case PY_CODE_LOCATION_INFO_ONE_LINE2: {
int line_delta = code - 10;
info->lineno += line_delta;
info->end_lineno = info->lineno;
case PY_CODE_LOCATION_INFO_ONE_LINE2:
computed_line += code - 10;
info->lineno = info->end_lineno = computed_line;
info->column = *(ptr++);
info->end_column = *(ptr++);
break;
}
default: {
uint8_t second_byte = *(ptr++);
if ((second_byte & 128) != 0) {
return false;
}
info->lineno = info->end_lineno = computed_line;
info->column = code << 3 | (second_byte >> 4);
info->end_column = info->column + (second_byte & 15);
break;
@ -215,8 +212,25 @@ parse_linetable(const uintptr_t addrq, const char* linetable, int firstlineno, L
* ============================================================================ */
PyObject *
make_frame_info(RemoteUnwinderObject *unwinder, PyObject *file, PyObject *line,
PyObject *func)
make_location_info(RemoteUnwinderObject *unwinder, int lineno, int end_lineno,
int col_offset, int end_col_offset)
{
RemoteDebuggingState *state = RemoteDebugging_GetStateFromObject((PyObject*)unwinder);
PyObject *info = PyStructSequence_New(state->LocationInfo_Type);
if (info == NULL) {
set_exception_cause(unwinder, PyExc_MemoryError, "Failed to create LocationInfo");
return NULL;
}
PyStructSequence_SetItem(info, 0, PyLong_FromLong(lineno));
PyStructSequence_SetItem(info, 1, PyLong_FromLong(end_lineno));
PyStructSequence_SetItem(info, 2, PyLong_FromLong(col_offset));
PyStructSequence_SetItem(info, 3, PyLong_FromLong(end_col_offset));
return info;
}
PyObject *
make_frame_info(RemoteUnwinderObject *unwinder, PyObject *file, PyObject *location,
PyObject *func, PyObject *opcode)
{
RemoteDebuggingState *state = RemoteDebugging_GetStateFromObject((PyObject*)unwinder);
PyObject *info = PyStructSequence_New(state->FrameInfo_Type);
@ -225,11 +239,13 @@ make_frame_info(RemoteUnwinderObject *unwinder, PyObject *file, PyObject *line,
return NULL;
}
Py_INCREF(file);
Py_INCREF(line);
Py_INCREF(location);
Py_INCREF(func);
Py_INCREF(opcode);
PyStructSequence_SetItem(info, 0, file);
PyStructSequence_SetItem(info, 1, line);
PyStructSequence_SetItem(info, 1, location);
PyStructSequence_SetItem(info, 2, func);
PyStructSequence_SetItem(info, 3, opcode);
return info;
}
@ -365,16 +381,43 @@ parse_code_object(RemoteUnwinderObject *unwinder,
meta->first_lineno, &info);
if (!ok) {
info.lineno = -1;
info.end_lineno = -1;
info.column = -1;
info.end_column = -1;
}
PyObject *lineno = PyLong_FromLong(info.lineno);
if (!lineno) {
set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to create line number object");
// Create the LocationInfo structseq: (lineno, end_lineno, col_offset, end_col_offset)
PyObject *location = make_location_info(unwinder,
info.lineno,
info.end_lineno,
info.column,
info.end_column);
if (!location) {
goto error;
}
PyObject *tuple = make_frame_info(unwinder, meta->file_name, lineno, meta->func_name);
Py_DECREF(lineno);
// Read the instruction opcode from target process if opcodes flag is set
PyObject *opcode_obj = NULL;
if (unwinder->opcodes) {
uint16_t instruction_word = 0;
if (_Py_RemoteDebug_PagedReadRemoteMemory(&unwinder->handle, ip,
sizeof(uint16_t), &instruction_word) == 0) {
opcode_obj = PyLong_FromLong(instruction_word & 0xFF);
if (!opcode_obj) {
Py_DECREF(location);
set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to create opcode object");
goto error;
}
} else {
// Opcode read failed - clear the exception since opcode is optional
PyErr_Clear();
}
}
PyObject *tuple = make_frame_info(unwinder, meta->file_name, location,
meta->func_name, opcode_obj ? opcode_obj : Py_None);
Py_DECREF(location);
Py_XDECREF(opcode_obj);
if (!tuple) {
goto error;
}