diff options
Diffstat (limited to 'features/rt/signal-x86-Delay-calling-signals-in-atomic.patch')
| -rw-r--r-- | features/rt/signal-x86-Delay-calling-signals-in-atomic.patch | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/features/rt/signal-x86-Delay-calling-signals-in-atomic.patch b/features/rt/signal-x86-Delay-calling-signals-in-atomic.patch new file mode 100644 index 00000000..6e4be111 --- /dev/null +++ b/features/rt/signal-x86-Delay-calling-signals-in-atomic.patch @@ -0,0 +1,139 @@ +From 3cbbc9627110b6a4140d688a54c57711d3ba8560 Mon Sep 17 00:00:00 2001 +From: Oleg Nesterov <oleg@redhat.com> +Date: Tue, 14 Jul 2015 14:26:34 +0200 +Subject: [PATCH 100/191] signal/x86: Delay calling signals in atomic + +On x86_64 we must disable preemption before we enable interrupts +for stack faults, int3 and debugging, because the current task is using +a per CPU debug stack defined by the IST. If we schedule out, another task +can come in and use the same stack and cause the stack to be corrupted +and crash the kernel on return. + +When CONFIG_PREEMPT_RT is enabled, spin_locks become mutexes, and +one of these is the spin lock used in signal handling. + +Some of the debug code (int3) causes do_trap() to send a signal. +This function calls a spin lock that has been converted to a mutex +and has the possibility to sleep. If this happens, the above issues with +the corrupted stack is possible. + +Instead of calling the signal right away, for PREEMPT_RT and x86_64, +the signal information is stored on the stacks task_struct and +TIF_NOTIFY_RESUME is set. Then on exit of the trap, the signal resume +code will send the signal when preemption is enabled. + +[ rostedt: Switched from #ifdef CONFIG_PREEMPT_RT to + ARCH_RT_DELAYS_SIGNAL_SEND and added comments to the code. ] + +Signed-off-by: Oleg Nesterov <oleg@redhat.com> +Signed-off-by: Steven Rostedt <rostedt@goodmis.org> +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +[bigeasy: also needed on 32bit as per Yang Shi <yang.shi@linaro.org>] +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + arch/x86/include/asm/signal.h | 13 +++++++++++++ + include/linux/sched.h | 4 ++++ + kernel/entry/common.c | 8 ++++++++ + kernel/signal.c | 28 ++++++++++++++++++++++++++++ + 4 files changed, 53 insertions(+) + +diff --git a/arch/x86/include/asm/signal.h b/arch/x86/include/asm/signal.h +index 6fd8410a3910..f3bf2f515edb 100644 +--- a/arch/x86/include/asm/signal.h ++++ b/arch/x86/include/asm/signal.h +@@ -28,6 +28,19 @@ typedef struct { + #define SA_IA32_ABI 0x02000000u + #define SA_X32_ABI 0x01000000u + ++/* ++ * Because some traps use the IST stack, we must keep preemption ++ * disabled while calling do_trap(), but do_trap() may call ++ * force_sig_info() which will grab the signal spin_locks for the ++ * task, which in PREEMPT_RT are mutexes. By defining ++ * ARCH_RT_DELAYS_SIGNAL_SEND the force_sig_info() will set ++ * TIF_NOTIFY_RESUME and set up the signal to be sent on exit of the ++ * trap. ++ */ ++#if defined(CONFIG_PREEMPT_RT) ++#define ARCH_RT_DELAYS_SIGNAL_SEND ++#endif ++ + #ifndef CONFIG_COMPAT + typedef sigset_t compat_sigset_t; + #endif +diff --git a/include/linux/sched.h b/include/linux/sched.h +index fb5350358bc8..1d85cfa28fe6 100644 +--- a/include/linux/sched.h ++++ b/include/linux/sched.h +@@ -997,6 +997,10 @@ struct task_struct { + /* Restored if set_restore_sigmask() was used: */ + sigset_t saved_sigmask; + struct sigpending pending; ++#ifdef CONFIG_PREEMPT_RT ++ /* TODO: move me into ->restart_block ? */ ++ struct kernel_siginfo forced_info; ++#endif + unsigned long sas_ss_sp; + size_t sas_ss_size; + unsigned int sas_ss_flags; +diff --git a/kernel/entry/common.c b/kernel/entry/common.c +index 8442e5c9cfa2..2a7bcc744033 100644 +--- a/kernel/entry/common.c ++++ b/kernel/entry/common.c +@@ -161,6 +161,14 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, + if (ti_work & _TIF_NEED_RESCHED) + schedule(); + ++#ifdef ARCH_RT_DELAYS_SIGNAL_SEND ++ if (unlikely(current->forced_info.si_signo)) { ++ struct task_struct *t = current; ++ force_sig_info(&t->forced_info); ++ t->forced_info.si_signo = 0; ++ } ++#endif ++ + if (ti_work & _TIF_UPROBE) + uprobe_notify_resume(regs); + +diff --git a/kernel/signal.c b/kernel/signal.c +index 98c48e1ea82e..a5d16084f54c 100644 +--- a/kernel/signal.c ++++ b/kernel/signal.c +@@ -1314,6 +1314,34 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t) + struct k_sigaction *action; + int sig = info->si_signo; + ++ /* ++ * On some archs, PREEMPT_RT has to delay sending a signal from a trap ++ * since it can not enable preemption, and the signal code's spin_locks ++ * turn into mutexes. Instead, it must set TIF_NOTIFY_RESUME which will ++ * send the signal on exit of the trap. ++ */ ++#ifdef ARCH_RT_DELAYS_SIGNAL_SEND ++ if (in_atomic()) { ++ struct task_struct *t = current; ++ ++ if (WARN_ON_ONCE(t->forced_info.si_signo)) ++ return 0; ++ ++ if (is_si_special(info)) { ++ WARN_ON_ONCE(info != SEND_SIG_PRIV); ++ t->forced_info.si_signo = info->si_signo; ++ t->forced_info.si_errno = 0; ++ t->forced_info.si_code = SI_KERNEL; ++ t->forced_info.si_pid = 0; ++ t->forced_info.si_uid = 0; ++ } else { ++ t->forced_info = *info; ++ } ++ ++ set_tsk_thread_flag(t, TIF_NOTIFY_RESUME); ++ return 0; ++ } ++#endif + spin_lock_irqsave(&t->sighand->siglock, flags); + action = &t->sighand->action[sig-1]; + ignored = action->sa.sa_handler == SIG_IGN; +-- +2.19.1 + |