diff options
Diffstat (limited to 'debian/patches-rt/0064-signal-x86-Delay-calling-signals-in-atomic.patch')
| -rw-r--r-- | debian/patches-rt/0064-signal-x86-Delay-calling-signals-in-atomic.patch | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/debian/patches-rt/0064-signal-x86-Delay-calling-signals-in-atomic.patch b/debian/patches-rt/0064-signal-x86-Delay-calling-signals-in-atomic.patch new file mode 100644 index 000000000..8acb6a058 --- /dev/null +++ b/debian/patches-rt/0064-signal-x86-Delay-calling-signals-in-atomic.patch @@ -0,0 +1,154 @@ +From 47c69a6b85d4820b49840b1bd914a970e7eb6851 Mon Sep 17 00:00:00 2001 +From: Oleg Nesterov <oleg@redhat.com> +Date: Tue, 14 Jul 2015 14:26:34 +0200 +Subject: [PATCH 064/347] signal/x86: Delay calling signals in atomic +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +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_FULL 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_FULL 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> +--- + arch/x86/entry/common.c | 7 +++++++ + arch/x86/include/asm/signal.h | 13 ++++++++++++ + include/linux/sched.h | 4 ++++ + kernel/signal.c | 37 +++++++++++++++++++++++++++++++++-- + 4 files changed, 59 insertions(+), 2 deletions(-) + +diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c +index 8353348ddeaf..91676b0d2d4c 100644 +--- a/arch/x86/entry/common.c ++++ b/arch/x86/entry/common.c +@@ -152,6 +152,13 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags) + if (cached_flags & _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.si_signo, &t->forced_info, t); ++ t->forced_info.si_signo = 0; ++ } ++#endif + if (cached_flags & _TIF_UPROBE) + uprobe_notify_resume(regs); + +diff --git a/arch/x86/include/asm/signal.h b/arch/x86/include/asm/signal.h +index 33d3c88a7225..fb0438d06ca7 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_FULL 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_FULL) && defined(CONFIG_X86_64) ++#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 52069b9ddce8..56047f57ebc7 100644 +--- a/include/linux/sched.h ++++ b/include/linux/sched.h +@@ -881,6 +881,10 @@ struct task_struct { + /* Restored if set_restore_sigmask() was used: */ + sigset_t saved_sigmask; + struct sigpending pending; ++#ifdef CONFIG_PREEMPT_RT_FULL ++ /* TODO: move me into ->restart_block ? */ ++ struct siginfo forced_info; ++#endif + unsigned long sas_ss_sp; + size_t sas_ss_size; + unsigned int sas_ss_flags; +diff --git a/kernel/signal.c b/kernel/signal.c +index 23764988b5d1..58bd3b3dd499 100644 +--- a/kernel/signal.c ++++ b/kernel/signal.c +@@ -1283,8 +1283,8 @@ int do_send_sig_info(int sig, struct siginfo *info, struct task_struct *p, + * We don't want to have recursive SIGSEGV's etc, for example, + * that is why we also clear SIGNAL_UNKILLABLE. + */ +-int +-force_sig_info(int sig, struct siginfo *info, struct task_struct *t) ++static int ++do_force_sig_info(int sig, struct siginfo *info, struct task_struct *t) + { + unsigned long int flags; + int ret, blocked, ignored; +@@ -1313,6 +1313,39 @@ force_sig_info(int sig, struct siginfo *info, struct task_struct *t) + return ret; + } + ++int force_sig_info(int sig, struct siginfo *info, struct task_struct *t) ++{ ++/* ++ * 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()) { ++ if (WARN_ON_ONCE(t != current)) ++ return 0; ++ 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 = sig; ++ 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 ++ return do_force_sig_info(sig, info, t); ++} ++ + /* + * Nuke all other threads in the group. + */ +-- +2.36.1 + |