From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Eric W. Biederman" Date: Wed, 04 May 2022 22:39:33 +0000 Subject: [PATCH v3 0/11] ptrace: cleaning up ptrace_stop Message-Id: <87k0b0apne.fsf_-_@email.froward.int.ebiederm.org> List-Id: References: <20220421150248.667412396@infradead.org> <20220421150654.817117821@infradead.org> <87czhap9dy.fsf@email.froward.int.ebiederm.org> <878rrrh32q.fsf_-_@email.froward.int.ebiederm.org> <87k0b7v9yk.fsf_-_@email.froward.int.ebiederm.org> In-Reply-To: <87k0b7v9yk.fsf_-_@email.froward.int.ebiederm.org> (Eric W. Biederman's message of "Fri, 29 Apr 2022 16:46:59 -0500") MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-kernel@vger.kernel.org Cc: rjw@rjwysocki.net, oleg@redhat.com, mingo@kernel.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, mgorman@suse.de, bigeasy@linutronix.de, Will Deacon , tj@kernel.org, linux-pm@vger.kernel.org, Peter Zijlstra , Richard Weinberger , Anton Ivanov , Johannes Berg , linux-um@lists.infradead.org, Chris Zankel , Max Filippov , linux-xtensa@linux-xtensa.org, Jann Horn , Kees Cook , linux-ia64@vger.kernel.org The states TASK_STOPPED and TASK_TRACE are special in they can not handle spurious wake-ups. This plus actively depending upon and changing the value of tsk->__state causes problems for PREEMPT_RT and Peter's freezer rewrite. There are a lot of details we have to get right to sort out the technical challenges and this is my parred back version of the changes that contains just those problems I see good solutions to that I believe are ready. A couple of issues have been pointed but I think this parred back set of changes is still on the right track. The biggest change in v3 is that instead of trying to prevent sending a spurious SIGTRAP when the tracer dies with the tracee in ptrace_report_syscall, I have modified the code to just stop trying. While I still have taken TASK_WAKEKILL out of TASK_TRACED I have implemented simpler logic in signal_wake_up. Further I have followed Oleg's advice and exit early from ptrace_stop if a fatal signal is pending. This set of changes should support Peter's freezer rewrite, and with the addition of changing wait_task_inactive(TASK_TRACED) to be wait_task_inactive(0) in ptrace_check_attach I don't think there are any races or issues to be concerned about from the ptrace side. More work is needed to support PREEMPT_RT, but these changes get things closer. I believe this set of changes will provide a firm foundation for solving the PREEMPT_RT and freezer challenges. With fewer lines added and more lines removed this set of changes looks like it is moving in a good direction. Eric W. Biederman (10): signal: Rename send_signal send_signal_locked signal: Replace __group_send_sig_info with send_signal_locked ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP ptrace/xtensa: Replace PT_SINGLESTEP with TIF_SINGLESTEP ptrace: Remove arch_ptrace_attach signal: Use lockdep_assert_held instead of assert_spin_locked ptrace: Reimplement PTRACE_KILL by always sending SIGKILL ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs ptrace: Don't change __state ptrace: Always take siglock in ptrace_resume Peter Zijlstra (1): sched,signal,ptrace: Rework TASK_TRACED, TASK_STOPPED state arch/ia64/include/asm/ptrace.h | 4 -- arch/ia64/kernel/ptrace.c | 57 ---------------- arch/um/include/asm/thread_info.h | 2 + arch/um/kernel/exec.c | 2 +- arch/um/kernel/process.c | 2 +- arch/um/kernel/ptrace.c | 8 +-- arch/um/kernel/signal.c | 4 +- arch/x86/kernel/step.c | 3 +- arch/xtensa/kernel/ptrace.c | 4 +- arch/xtensa/kernel/signal.c | 4 +- drivers/tty/tty_jobctrl.c | 4 +- include/linux/ptrace.h | 7 -- include/linux/sched.h | 10 ++- include/linux/sched/jobctl.h | 8 +++ include/linux/sched/signal.h | 20 ++++-- include/linux/signal.h | 3 +- kernel/ptrace.c | 87 ++++++++---------------- kernel/sched/core.c | 5 +- kernel/signal.c | 135 +++++++++++++++++--------------------- kernel/time/posix-cpu-timers.c | 6 +- 20 files changed, 138 insertions(+), 237 deletions(-) Eric