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Isolate the faulthandler Module Between Interpreters #101509

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Isolate the faulthandler Module Between Interpreters#101509

Labels

3.12only security fixesinterpreter-core(Objects, Python, Grammar, and Parser dirs)topic-subinterpreterstype-featureA feature request or enhancement

Description

ericsnowcurrently

opened

on Feb 1, 2023

(Seegh-100227.)

Currently the faulthandler module has some state in_PyRuntimeState, including objects, which is shared by all interpreters. Interpreters should be isolated from each other, for a variety of reasons (including the possibility of a per-interpreter GIL). Isolating the module will involve moving some of the state toPyInterpreterState (and, under per-interpreter GIL, guarding other state with a global lock).

Code Analysis:

(expand)

Signals

The module installs handlers for various signals.

(expand)

fatal:

SIGBUS - bus error
SIGILL - illegal instruction
SIGFPE - floating point exception
SIGABRT - abort
SIGSEGV - segfault

"user":

the 5 fatal signals
others (up toPy_NSIG)

handlers:

faulthandler_fatal_error(signum)
faulthandler_exc_handler() (on Windows)
faulthandler_user()

State

Fields

https://github.com/python/cpython/blob/main/Include/internal/pycore_faulthandler.h#L49-L86
https://github.com/python/cpython/blob/main/Include/internal/pycore_runtime.h#L146

raw

cpython/Include/internal/pycore_faulthandler.h

Lines 49 to 86 in62251c3

	struct_faulthandler_runtime_state {
	struct {
	intenabled;
	PyObject*file;
	intfd;
	intall_threads;
	PyInterpreterState*interp;
	#ifdefMS_WINDOWS
	void*exc_handler;
	#endif
	}fatal_error;

	struct {
	PyObject*file;
	intfd;
	PY_TIMEOUT_Ttimeout_us;/* timeout in microseconds */
	intrepeat;
	PyInterpreterState*interp;
	intexit;
	char*header;
	size_theader_len;
	/* The main thread always holds this lock. It is only released when
	faulthandler_thread() is interrupted before this thread exits, or at
	Python exit. */
	PyThread_type_lockcancel_event;
	/* released by child thread when joined */
	PyThread_type_lockrunning;
	}thread;

	#ifdefFAULTHANDLER_USER
	structfaulthandler_user_signal*user_signals;
	#endif

	#ifdefFAULTHANDLER_USE_ALT_STACK
	stack_tstack;
	stack_told_stack;
	#endif
	};

cpython/Include/internal/pycore_faulthandler.h

Lines 36 to 46 in62251c3

	#ifdefFAULTHANDLER_USER
	structfaulthandler_user_signal {
	intenabled;
	PyObject*file;
	intfd;
	intall_threads;
	intchain;
	_Py_sighandler_tprevious;
	PyInterpreterState*interp;
	};
	#endif/* FAULTHANDLER_USER */

tables:

name	type	#ifdef	notes
`fatal_error`
.`enabled`	`bool`		"is faulthandler enabled?"
.`file`	*`PyObject `**		only for keeping`.fd` alive
.`fd`	`int`
.`all_threads`	`bool`
.`interp`	*`PyInterpreterState `**		show only its threads the one that enabled faulthandler
.`exc_handler`	`void *`	`MS_WINDOWS`

name	type	#ifdef	notes
`thread`	---
.`file`	`PyObject `*		only for keeping`.fd` alive
.`fd`	`int`		defaults to`sys.stderr`
.`timeout_us`	`PY_TIMEOUT_T`
.`repeat`	`bool`
.`interp`	*`PyInterpreterState `**		show only its threads the one that requested the info
.`exit`	`bool`
.`header`	`char *`
.`header_len`	`size_t`
.`cancel_event`	`PyThread_type_lock`
.`running`	`PyThread_type_lock`
name	type	#ifdef	notes
`user_signals`	*`struct faulthandler_user_signal `**	`FAULTHANDLER_USER`	a dynamically allocated array (`Py_NSIG`)
`user_signals[signum]`	---
.`enabled`	`bool`
.`file`	`PyObject *`
.`fd`	`int`
.`all_threads`	`bool`
.`chain`	`bool`
.`previous`	`_Py_sighandler_t`
.`interp`	*`PyInterpreterState `**		show only its threads the one that added the handler
name	type	#ifdef	notes
`old_stack`	`stack_t`	`FAULTHANDLER_USE_ALT_STACK`
`stack`	`stack_t`	`FAULTHANDLER_USE_ALT_STACK`

Usage

simple:

name	context	get	set
`fatal_error`
.`enabled`	module	`faulthandler_is_enabled()`	`faulthandler_disable_py()`
	signal	`faulthandler_fatal_error()`
	internal	`faulthandler_enable()` `faulthandler_disable()`	`faulthandler_enable()` `faulthandler_disable()`
.`file`	module	`faulthandler_traverse()`	`faulthandler_py_enable()` `faulthandler_traverse()`
	internal	`faulthandler_disable()`	`faulthandler_disable()`
.`fd`		module
	signal	`faulthandler_fatal_error()` `faulthandler_exc_handler()`
.`all_threads`	module		`faulthandler_py_enable()`
	signal	`faulthandler_fatal_error()` `faulthandler_exc_handler()`
.`interp`	module		`faulthandler_py_enable()`
	internal	`faulthandler_fatal_error()` `faulthandler_exc_handler()`
.`exc_handler`	internal	`faulthandler_enable()` `faulthandler_disable()`	`faulthandler_enable()` `faulthandler_disable()`

name	context	get	set
`thread`
.`file`	module	`faulthandler_dump_traceback_later()` `faulthandler_traverse()`	`faulthandler_dump_traceback_later()` `faulthandler_traverse()`
	internal	`cancel_dump_traceback_later()`	`cancel_dump_traceback_later()`
.`fd`
module		`faulthandler_dump_traceback_later()`
	thread	`faulthandler_thread()`
.`timeout_us`	module		`faulthandler_dump_traceback_later()`
	thread	`faulthandler_thread()`
.`repeat`	module		`faulthandler_dump_traceback_later()`
	thread	`faulthandler_thread()`
.`interp`	module		`faulthandler_dump_traceback_later()`
	thread	`faulthandler_thread()`
.`exit`	module		`faulthandler_dump_traceback_later()`
	thread	`faulthandler_thread()`
.`header`	module		`faulthandler_dump_traceback_later()`
	thread	`faulthandler_thread()`
	internal	`cancel_dump_traceback_later()`	`cancel_dump_traceback_later()`
.`header_len`	module		`faulthandler_dump_traceback_later()`
	thread	`faulthandler_thread()`
.`cancel_event`	module	`faulthandler_dump_traceback_later()`	`faulthandler_dump_traceback_later()`
	thread	`faulthandler_thread()`
	internal	`cancel_dump_traceback_later()`
.`running`	module	`faulthandler_dump_traceback_later()`	`faulthandler_dump_traceback_later()`
	thread	`faulthandler_thread()`
	internal	`cancel_dump_traceback_later()`
name	context	get	set
`user_signals`	module	`faulthandler_register_py()` `faulthandler_unregister_py()`	`faulthandler_register_py()` `faulthandler_traverse()`
	C-API	`_PyFaulthandler_Fini()`	`_PyFaulthandler_Fini()`
	signal	`faulthandler_user()`
`user_signals[signum]`
.`enabled`	module	`faulthandler_register_py()`	`faulthandler_register_py()`
	signal	`faulthandler_user()`
	internal	`faulthandler_unregister()`	`faulthandler_unregister()`
.`file`	module	`faulthandler_register_py()` `faulthandler_traverse()`	`faulthandler_register_py()` `faulthandler_traverse()`
	internal	`faulthandler_unregister()`	`faulthandler_unregister()`
.`fd`	module		`faulthandler_register_py()`
	signal	`faulthandler_user()`
	internal		`faulthandler_unregister()`
.`all_threads`	module		`faulthandler_register_py()`
	signal	`faulthandler_user()`
.`chain`	module		`faulthandler_register_py()`
	signal	`faulthandler_user()`
.`previous`	module		`faulthandler_register_py()`
	signal	`faulthandler_user()`
	internal	`faulthandler_unregister()`
.`interp`	module		`faulthandler_register_py()`
	signal	`faulthandler_user()`
name	context	get	set
`stack`	C-API	`_PyFaulthandler_Init()` `_PyFaulthandler_Fini()`
	internal	`faulthandler_enable()` `faulthandler_register()` `faulthandler_allocate_stack()`
`old_stack`	C-API	`_PyFaulthandler_Fini()`

modify data in complex fields:

name	context	calls
`fatal_error .fd`	signal	`faulthandler_fatal_error()` ->`faulthandler_dump_traceback()` `faulthandler_fatal_error()` ->`_Py_DumpExtensionModules()` `faulthandler_exc_handler()` `faulthandler_exc_handler()` ->`_Py_DumpHexadecimal()` `faulthandler_exc_handler()` ->`faulthandler_dump_traceback()`
`thread.fd`	thread	`faulthandler_thread()` ->`_Py_write_noraise()` `faulthandler_thread()` ->`_Py_DumpTracebackThreads()`
`thread .cancel_event`	module	`faulthandler_dump_traceback_later()`
	C-API	`_PyFaulthandler_Fini()`
	thread	`faulthandler_thread()`
	internal	`cancel_dump_traceback_later()`
`thread .running`	module	`faulthandler_dump_traceback_later()`
	thread	`faulthandler_thread()`
	internal	`cancel_dump_traceback_later()`
`user_signals[signum] .fd`	signal	`faulthandler_user()` ->`faulthandler_dump_traceback()`
`stack`	C-API	`_PyFaulthandler_Init()` `_PyFaulthandler_Fini()`
	internal	`faulthandler_allocate_stack()`
`old_stack`	internal	`faulthandler_allocate_stack()` ->`sigaltstack()`

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Isolate the faulthandler Module Between Interpreters #101509

Description

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