Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752379AbcDRPBT (ORCPT ); Mon, 18 Apr 2016 11:01:19 -0400 Received: from mx2.suse.de ([195.135.220.15]:38230 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751649AbcDRPBQ (ORCPT ); Mon, 18 Apr 2016 11:01:16 -0400 From: Miroslav Benes To: jpoimboe@redhat.com Cc: jikos@kernel.org, jeyu@redhat.com, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, vojtech@suse.com, jslaby@suse.cz, pmladek@suse.cz, Miroslav Benes Subject: [RFC PATCH 2/2] s390/klp: update task universe when exiting kernel Date: Mon, 18 Apr 2016 17:01:10 +0200 Message-Id: <1460991670-32187-3-git-send-email-mbenes@suse.cz> X-Mailer: git-send-email 2.8.1 In-Reply-To: <1460991670-32187-1-git-send-email-mbenes@suse.cz> References: <20160414133951.eydmvevb65jzse5e@treble> <1460991670-32187-1-git-send-email-mbenes@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4122 Lines: 115 Update a tasks's universe when returning from a system call or user space interrupt, or after handling a signal. This greatly increases the chances of a patch operation succeeding. If a task is I/O bound, it can switch universes when returning from a system call. If a task is CPU bound, it can switch universes when returning from an interrupt. If a task is sleeping on a to-be-patched function, the user can send SIGSTOP and SIGCONT to force it to switch. Since there are two ways how the syscall can be restarted on return from a signal handling process, it is important to clear the flag before do_signal() is called. Otherwise we could miss the migration if we used SIGSTOP/SIGCONT procedure or fake signal to migrate patching blocking tasks. If we place our hook to sysc_work label in entry before TIF_SIGPENDING is evaluated we kill two birds with one stone. The task is correctly migrated in all return paths from a syscall. Signed-off-by: Miroslav Benes --- arch/s390/include/asm/thread_info.h | 2 ++ arch/s390/kernel/entry.S | 31 ++++++++++++++++++++++++++++++- 2 files changed, 32 insertions(+), 1 deletion(-) diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h index 8642c1dab382..451dd2ddc3be 100644 --- a/arch/s390/include/asm/thread_info.h +++ b/arch/s390/include/asm/thread_info.h @@ -75,6 +75,7 @@ void arch_release_task_struct(struct task_struct *tsk); #define TIF_SIGPENDING 1 /* signal pending */ #define TIF_NEED_RESCHED 2 /* rescheduling necessary */ #define TIF_UPROBE 3 /* breakpointed or single-stepping */ +#define TIF_KLP_NEED_UPDATE 4 /* pending live patching update */ #define TIF_31BIT 16 /* 32bit process */ #define TIF_MEMDIE 17 /* is terminating due to OOM killer */ @@ -93,6 +94,7 @@ void arch_release_task_struct(struct task_struct *tsk); #define _TIF_SIGPENDING _BITUL(TIF_SIGPENDING) #define _TIF_NEED_RESCHED _BITUL(TIF_NEED_RESCHED) #define _TIF_UPROBE _BITUL(TIF_UPROBE) +#define _TIF_KLP_NEED_UPDATE _BITUL(TIF_KLP_NEED_UPDATE) #define _TIF_31BIT _BITUL(TIF_31BIT) #define _TIF_SINGLE_STEP _BITUL(TIF_SINGLE_STEP) diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index 2d47f9cfcb36..cbc3a3b4aa6e 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -46,7 +46,7 @@ STACK_SIZE = 1 << STACK_SHIFT STACK_INIT = STACK_SIZE - STACK_FRAME_OVERHEAD - __PT_SIZE _TIF_WORK = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \ - _TIF_UPROBE) + _TIF_UPROBE | _TIF_KLP_NEED_UPDATE ) _TIF_TRACE = (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \ _TIF_SYSCALL_TRACEPOINT) _CIF_WORK = (_CIF_MCCK_PENDING | _CIF_ASCE | _CIF_FPU) @@ -329,6 +329,11 @@ ENTRY(system_call) #endif TSTMSK __PT_FLAGS(%r11),_PIF_PER_TRAP jo .Lsysc_singlestep +#ifdef CONFIG_LIVEPATCH + TSTMSK __TI_flags(%r12),_TIF_KLP_NEED_UPDATE + jo .Lsysc_update_klp # handle KLP just before signals and + # possible syscall restart +#endif TSTMSK __TI_flags(%r12),_TIF_SIGPENDING jo .Lsysc_sigpending TSTMSK __TI_flags(%r12),_TIF_NOTIFY_RESUME @@ -404,6 +409,16 @@ ENTRY(system_call) #endif # +# _TIF_KLP_NEED_UPDATE is set, call klp_update_task_universe +# +#ifdef CONFIG_LIVEPATCH +.Lsysc_update_klp: + lg %r2,__TI_task(%r12) + larl %r14,.Lsysc_return + jg klp_update_task_universe +#endif + +# # _PIF_PER_TRAP is set, call do_per_trap # .Lsysc_singlestep: @@ -652,6 +667,10 @@ ENTRY(io_int_handler) jo .Lio_mcck_pending TSTMSK __TI_flags(%r12),_TIF_NEED_RESCHED jo .Lio_reschedule +#ifdef CONFIG_LIVEPATCH + TSTMSK __TI_flags(%r12),_TIF_KLP_NEED_UPDATE + jo .Lio_update_klp +#endif TSTMSK __TI_flags(%r12),_TIF_SIGPENDING jo .Lio_sigpending TSTMSK __TI_flags(%r12),_TIF_NOTIFY_RESUME @@ -698,6 +717,16 @@ ENTRY(io_int_handler) j .Lio_return # +# _TIF_KLP_NEED_UPDATE is set, call klp_update_task_universe +# +#ifdef CONFIG_LIVEPATCH +.Lio_update_klp: + lg %r2,__TI_task(%r12) + larl %r14,.Lio_return + jg klp_update_task_universe +#endif + +# # _TIF_SIGPENDING or is set, call do_signal # .Lio_sigpending: -- 2.8.1