pm24.git/kernel/panic.c, branch v5.2-rc1

panic: add an option to replay all the printk message in buffer

2019-05-18T22:52:26Z

Currently on panic, kernel will lower the loglevel and print out pending printk msg only with console_flush_on_panic(). Add an option for users to configure the "panic_print" to replay all dmesg in buffer, some of which they may have never seen due to the loglevel setting, which will help panic debugging . [feng.tang@intel.com: keep the original console_flush_on_panic() inside panic()] Link: http://lkml.kernel.org/r/1556199137-14163-1-git-send-email-feng.tang@intel.com [feng.tang@intel.com: use logbuf lock to protect the console log index] Link: http://lkml.kernel.org/r/1556269868-22654-1-git-send-email-feng.tang@intel.com Link: http://lkml.kernel.org/r/1556095872-36838-1-git-send-email-feng.tang@intel.com Signed-off-by: Feng Tang Reviewed-by: Petr Mladek Cc: Aaro Koskinen Cc: Petr Mladek Cc: Steven Rostedt Cc: Sergey Senozhatsky Cc: Kees Cook Cc: Borislav Petkov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

panic/reboot: allow specifying reboot_mode for panic only

2019-05-15T02:52:51Z

Allow specifying reboot_mode for panic only. This is needed on systems where ramoops is used to store panic logs, and user wants to use warm reset to preserve those, while still having cold reset on normal reboots. Link: http://lkml.kernel.org/r/20190322004735.27702-1-aaro.koskinen@iki.fi Signed-off-by: Aaro Koskinen Reviewed-by: Kees Cook Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

panic: avoid the extra noise dmesg

2019-05-15T02:52:51Z

When kernel panic happens, it will first print the panic call stack, then the ending msg like: [ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception [ 35.749975] ------------[ cut here ]------------ The above message are very useful for debugging. But if system is configured to not reboot on panic, say the "panic_timeout" parameter equals 0, it will likely print out many noisy message like WARN() call stack for each and every CPU except the panic one, messages like below: WARNING: CPU: 1 PID: 280 at kernel/sched/core.c:1198 set_task_cpu+0x183/0x190 Call Trace: try_to_wake_up default_wake_function autoremove_wake_function __wake_up_common __wake_up_common_lock __wake_up wake_up_klogd_work_func irq_work_run_list irq_work_tick update_process_times tick_sched_timer __hrtimer_run_queues hrtimer_interrupt smp_apic_timer_interrupt apic_timer_interrupt For people working in console mode, the screen will first show the panic call stack, but immediately overridden by these noisy extra messages, which makes debugging much more difficult, as the original context gets lost on screen. Also these noisy messages will confuse some users, as I have seen many bug reporters posted the noisy message into bugzilla, instead of the real panic call stack and context. Adding a flag "suppress_printk" which gets set in panic() to avoid those noisy messages, without changing current kernel behavior that both panic blinking and sysrq magic key can work as is, suggested by Petr Mladek. To verify this, make sure kernel is not configured to reboot on panic and in console # echo c > /proc/sysrq-trigger to see if console only prints out the panic call stack. Link: http://lkml.kernel.org/r/1551430186-24169-1-git-send-email-feng.tang@intel.com Signed-off-by: Feng Tang Suggested-by: Petr Mladek Reviewed-by: Petr Mladek Acked-by: Steven Rostedt (VMware) Acked-by: Sergey Senozhatsky Cc: Thomas Gleixner Cc: Kees Cook Cc: Borislav Petkov Cc: Andi Kleen Cc: Peter Zijlstra Cc: Greg Kroah-Hartman Cc: Jiri Slaby Cc: Sasha Levin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

s390: simplify disabled_wait

2019-05-02T11:54:11Z

The disabled_wait() function uses its argument as the PSW address when it stops the CPU with a wait PSW that is disabled for interrupts. The different callers sometimes use a specific number like 0xdeadbeef to indicate a specific failure, the early boot code uses 0 and some other calls sites use __builtin_return_address(0). At the time a dump is created the current PSW and the registers of a CPU are written to lowcore to make them avaiable to the dump analysis tool. For a CPU stopped with disabled_wait the PSW and the registers do not really make sense together, the PSW address does not point to the function the registers belong to. Simplify disabled_wait() by using _THIS_IP_ for the PSW address and drop the argument to the function. Signed-off-by: Martin Schwidefsky

kernel/panic.c: taint: fix debugfs_simple_attr.cocci warnings

2019-03-08T02:31:59Z

Use DEFINE_DEBUGFS_ATTRIBUTE rather than DEFINE_SIMPLE_ATTRIBUTE for debugfs files. Semantic patch information: Rationale: DEFINE_SIMPLE_ATTRIBUTE + debugfs_create_file() imposes some significant overhead as compared to DEFINE_DEBUGFS_ATTRIBUTE + debugfs_create_file_unsafe(). Generated by: scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci The _unsafe() part suggests that some of them "safeness responsibilities" are now panic.c responsibilities. The patch is OK since panic's clear_warn_once_fops struct file_operations is safe against removal, so we don't have to use otherwise necessary debugfs_file_get()/debugfs_file_put(). [sergey.senozhatsky.work@gmail.com: changelog addition] Link: http://lkml.kernel.org/r/1545990861-158097-1-git-send-email-yuehaibing@huawei.com Signed-off-by: YueHaibing Reviewed-by: Sergey Senozhatsky Cc: Kees Cook Cc: Borislav Petkov Cc: Steven Rostedt (VMware) Cc: Petr Mladek Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/sysctl: add panic_print into sysctl

2019-01-04T21:13:47Z

So that we can also runtime chose to print out the needed system info for panic, other than setting the kernel cmdline. Link: http://lkml.kernel.org/r/1543398842-19295-3-git-send-email-feng.tang@intel.com Signed-off-by: Feng Tang Suggested-by: Steven Rostedt Acked-by: Steven Rostedt (VMware) Cc: Thomas Gleixner Cc: John Stultz Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Kees Cook Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

panic: add options to print system info when panic happens

2019-01-04T21:13:47Z

Kernel panic issues are always painful to debug, partially because it's not easy to get enough information of the context when panic happens. And we have ramoops and kdump for that, while this commit tries to provide a easier way to show the system info by adding a cmdline parameter, referring some idea from sysrq handler. Link: http://lkml.kernel.org/r/1543398842-19295-2-git-send-email-feng.tang@intel.com Signed-off-by: Feng Tang Reviewed-by: Kees Cook Acked-by: Steven Rostedt (VMware) Cc: Thomas Gleixner Cc: John Stultz Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Steven Rostedt Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'printk-for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

2018-12-27T19:24:43Z

Pull printk updates from Petr Mladek: - Keep spinlocks busted until the end of panic() - Fix races between calculating number of messages that would fit into user space buffers, filling the buffers, and switching printk.time parameter - Some code clean up * tag 'printk-for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: printk: Remove print_prefix() calls with NULL buffer. printk: fix printk_time race. printk: Make printk_emit() local function. panic: avoid deadlocks in re-entrant console drivers

panic: avoid deadlocks in re-entrant console drivers

2018-11-22T13:07:43Z

From printk()/serial console point of view panic() is special, because it may force CPU to re-enter printk() or/and serial console driver. Therefore, some of serial consoles drivers are re-entrant. E.g. 8250: serial8250_console_write() { if (port->sysrq) locked = 0; else if (oops_in_progress) locked = spin_trylock_irqsave(&port->lock, flags); else spin_lock_irqsave(&port->lock, flags); ... } panic() does set oops_in_progress via bust_spinlocks(1), so in theory we should be able to re-enter serial console driver from panic(): CPU0 uart_console_write() serial8250_console_write() // if (oops_in_progress) // spin_trylock_irqsave() call_console_drivers() console_unlock() console_flush_on_panic() bust_spinlocks(1) // oops_in_progress++ panic() spin_lock_irqsave(&port->lock, flags) // spin_lock_irqsave() serial8250_console_write() call_console_drivers() console_unlock() printk() ... However, this does not happen and we deadlock in serial console on port->lock spinlock. And the problem is that console_flush_on_panic() called after bust_spinlocks(0): void panic(const char *fmt, ...) { bust_spinlocks(1); ... bust_spinlocks(0); console_flush_on_panic(); ... } bust_spinlocks(0) decrements oops_in_progress, so oops_in_progress can go back to zero. Thus even re-entrant console drivers will simply spin on port->lock spinlock. Given that port->lock may already be locked either by a stopped CPU, or by the very same CPU we execute panic() on (for instance, NMI panic() on printing CPU) the system deadlocks and does not reboot. Fix this by removing bust_spinlocks(0), so oops_in_progress is always set in panic() now and, thus, re-entrant console drivers will trylock the port->lock instead of spinning on it forever, when we call them from console_flush_on_panic(). Link: http://lkml.kernel.org/r/20181025101036.6823-1-sergey.senozhatsky@gmail.com Cc: Steven Rostedt Cc: Daniel Wang Cc: Peter Zijlstra Cc: Andrew Morton Cc: Linus Torvalds Cc: Greg Kroah-Hartman Cc: Alan Cox Cc: Jiri Slaby Cc: Peter Feiner Cc: linux-serial@vger.kernel.org Cc: Sergey Senozhatsky Cc: stable@vger.kernel.org Signed-off-by: Sergey Senozhatsky Signed-off-by: Petr Mladek

kernel/panic.c: filter out a potential trailing newline

2018-10-31T15:54:14Z

If a call to panic() terminates the string with a \n , the result puts the closing brace ']---' on a newline because panic() itself adds \n too. Now, if one goes and removes the newline chars from all panic() invocations - and the stats right now look like this: ~300 calls with a \n ~500 calls without a \n one is destined to a neverending game of whack-a-mole because the usual thing to do is add a newline at the end of a string a function is supposed to print. Therefore, simply zap any \n at the end of the panic string to avoid touching so many places in the kernel. Link: http://lkml.kernel.org/r/20181009205019.2786-1-bp@alien8.de Signed-off-by: Borislav Petkov Acked-by: Kees Cook Reviewed-by: Steven Rostedt (VMware) Acked-by: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds