![Andi Kleen](/assets/img/avatar_default.png)
It's somewhat unlikely that it happens, but right now a race window between interrupts or machine checks or oopses could corrupt the tainted bitmap because it is modified in a non atomic fashion. Convert the taint variable to an unsigned long and use only atomic bit operations on it. Unfortunately this means the intvec sysctl functions cannot be used on it anymore. It turned out the taint sysctl handler could actually be simplified a bit (since it only increases capabilities) so this patch actually removes code. [akpm@linux-foundation.org: remove unneeded include] Signed-off-by: Andi Kleen <ak@linux.intel.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
385 lines
8.6 KiB
C
385 lines
8.6 KiB
C
/*
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* linux/kernel/panic.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*/
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/*
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* This function is used through-out the kernel (including mm and fs)
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* to indicate a major problem.
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*/
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/delay.h>
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#include <linux/reboot.h>
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#include <linux/notifier.h>
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#include <linux/init.h>
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#include <linux/sysrq.h>
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#include <linux/interrupt.h>
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#include <linux/nmi.h>
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#include <linux/kexec.h>
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#include <linux/debug_locks.h>
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#include <linux/random.h>
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#include <linux/kallsyms.h>
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int panic_on_oops;
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static unsigned long tainted_mask;
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static int pause_on_oops;
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static int pause_on_oops_flag;
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static DEFINE_SPINLOCK(pause_on_oops_lock);
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int panic_timeout;
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ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
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EXPORT_SYMBOL(panic_notifier_list);
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static int __init panic_setup(char *str)
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{
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panic_timeout = simple_strtoul(str, NULL, 0);
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return 1;
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}
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__setup("panic=", panic_setup);
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static long no_blink(long time)
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{
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return 0;
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}
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/* Returns how long it waited in ms */
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long (*panic_blink)(long time);
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EXPORT_SYMBOL(panic_blink);
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/**
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* panic - halt the system
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* @fmt: The text string to print
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*
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* Display a message, then perform cleanups.
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*
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* This function never returns.
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*/
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NORET_TYPE void panic(const char * fmt, ...)
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{
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long i;
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static char buf[1024];
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va_list args;
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#if defined(CONFIG_S390)
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unsigned long caller = (unsigned long) __builtin_return_address(0);
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#endif
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/*
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* It's possible to come here directly from a panic-assertion and not
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* have preempt disabled. Some functions called from here want
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* preempt to be disabled. No point enabling it later though...
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*/
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preempt_disable();
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bust_spinlocks(1);
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va_start(args, fmt);
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vsnprintf(buf, sizeof(buf), fmt, args);
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va_end(args);
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printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
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bust_spinlocks(0);
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/*
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* If we have crashed and we have a crash kernel loaded let it handle
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* everything else.
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* Do we want to call this before we try to display a message?
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*/
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crash_kexec(NULL);
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#ifdef CONFIG_SMP
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/*
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* Note smp_send_stop is the usual smp shutdown function, which
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* unfortunately means it may not be hardened to work in a panic
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* situation.
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*/
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smp_send_stop();
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#endif
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atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
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if (!panic_blink)
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panic_blink = no_blink;
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if (panic_timeout > 0) {
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/*
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* Delay timeout seconds before rebooting the machine.
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* We can't use the "normal" timers since we just panicked..
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*/
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printk(KERN_EMERG "Rebooting in %d seconds..",panic_timeout);
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for (i = 0; i < panic_timeout*1000; ) {
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touch_nmi_watchdog();
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i += panic_blink(i);
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mdelay(1);
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i++;
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}
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/* This will not be a clean reboot, with everything
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* shutting down. But if there is a chance of
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* rebooting the system it will be rebooted.
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*/
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emergency_restart();
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}
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#ifdef __sparc__
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{
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extern int stop_a_enabled;
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/* Make sure the user can actually press Stop-A (L1-A) */
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stop_a_enabled = 1;
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printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
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}
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#endif
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#if defined(CONFIG_S390)
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disabled_wait(caller);
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#endif
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local_irq_enable();
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for (i = 0;;) {
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touch_softlockup_watchdog();
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i += panic_blink(i);
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mdelay(1);
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i++;
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}
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}
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EXPORT_SYMBOL(panic);
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/**
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* print_tainted - return a string to represent the kernel taint state.
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*
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* 'P' - Proprietary module has been loaded.
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* 'F' - Module has been forcibly loaded.
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* 'S' - SMP with CPUs not designed for SMP.
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* 'R' - User forced a module unload.
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* 'M' - System experienced a machine check exception.
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* 'B' - System has hit bad_page.
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* 'U' - Userspace-defined naughtiness.
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* 'A' - ACPI table overridden.
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* 'W' - Taint on warning.
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*
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* The string is overwritten by the next call to print_taint().
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*/
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struct tnt {
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u8 bit;
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char true;
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char false;
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};
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static const struct tnt tnts[] = {
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{ TAINT_PROPRIETARY_MODULE, 'P', 'G' },
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{ TAINT_FORCED_MODULE, 'F', ' ' },
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{ TAINT_UNSAFE_SMP, 'S', ' ' },
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{ TAINT_FORCED_RMMOD, 'R', ' ' },
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{ TAINT_MACHINE_CHECK, 'M', ' ' },
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{ TAINT_BAD_PAGE, 'B', ' ' },
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{ TAINT_USER, 'U', ' ' },
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{ TAINT_DIE, 'D', ' ' },
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{ TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' },
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{ TAINT_WARN, 'W', ' ' },
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};
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const char *print_tainted(void)
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{
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static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
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if (tainted_mask) {
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char *s;
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int i;
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s = buf + sprintf(buf, "Tainted: ");
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for (i = 0; i < ARRAY_SIZE(tnts); i++) {
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const struct tnt *t = &tnts[i];
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*s++ = test_bit(t->bit, &tainted_mask) ?
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t->true : t->false;
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}
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*s = 0;
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} else
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snprintf(buf, sizeof(buf), "Not tainted");
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return(buf);
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}
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int test_taint(unsigned flag)
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{
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return test_bit(flag, &tainted_mask);
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}
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EXPORT_SYMBOL(test_taint);
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unsigned long get_taint(void)
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{
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return tainted_mask;
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}
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void add_taint(unsigned flag)
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{
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debug_locks = 0; /* can't trust the integrity of the kernel anymore */
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set_bit(flag, &tainted_mask);
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}
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EXPORT_SYMBOL(add_taint);
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static int __init pause_on_oops_setup(char *str)
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{
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pause_on_oops = simple_strtoul(str, NULL, 0);
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return 1;
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}
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__setup("pause_on_oops=", pause_on_oops_setup);
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static void spin_msec(int msecs)
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{
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int i;
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for (i = 0; i < msecs; i++) {
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touch_nmi_watchdog();
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mdelay(1);
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}
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}
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/*
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* It just happens that oops_enter() and oops_exit() are identically
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* implemented...
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*/
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static void do_oops_enter_exit(void)
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{
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unsigned long flags;
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static int spin_counter;
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if (!pause_on_oops)
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return;
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spin_lock_irqsave(&pause_on_oops_lock, flags);
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if (pause_on_oops_flag == 0) {
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/* This CPU may now print the oops message */
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pause_on_oops_flag = 1;
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} else {
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/* We need to stall this CPU */
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if (!spin_counter) {
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/* This CPU gets to do the counting */
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spin_counter = pause_on_oops;
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do {
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spin_unlock(&pause_on_oops_lock);
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spin_msec(MSEC_PER_SEC);
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spin_lock(&pause_on_oops_lock);
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} while (--spin_counter);
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pause_on_oops_flag = 0;
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} else {
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/* This CPU waits for a different one */
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while (spin_counter) {
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spin_unlock(&pause_on_oops_lock);
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spin_msec(1);
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spin_lock(&pause_on_oops_lock);
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}
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}
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}
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spin_unlock_irqrestore(&pause_on_oops_lock, flags);
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}
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/*
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* Return true if the calling CPU is allowed to print oops-related info. This
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* is a bit racy..
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*/
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int oops_may_print(void)
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{
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return pause_on_oops_flag == 0;
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}
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/*
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* Called when the architecture enters its oops handler, before it prints
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* anything. If this is the first CPU to oops, and it's oopsing the first time
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* then let it proceed.
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*
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* This is all enabled by the pause_on_oops kernel boot option. We do all this
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* to ensure that oopses don't scroll off the screen. It has the side-effect
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* of preventing later-oopsing CPUs from mucking up the display, too.
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*
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* It turns out that the CPU which is allowed to print ends up pausing for the
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* right duration, whereas all the other CPUs pause for twice as long: once in
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* oops_enter(), once in oops_exit().
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*/
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void oops_enter(void)
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{
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debug_locks_off(); /* can't trust the integrity of the kernel anymore */
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do_oops_enter_exit();
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}
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/*
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* 64-bit random ID for oopses:
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*/
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static u64 oops_id;
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static int init_oops_id(void)
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{
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if (!oops_id)
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get_random_bytes(&oops_id, sizeof(oops_id));
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return 0;
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}
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late_initcall(init_oops_id);
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static void print_oops_end_marker(void)
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{
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init_oops_id();
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printk(KERN_WARNING "---[ end trace %016llx ]---\n",
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(unsigned long long)oops_id);
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}
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/*
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* Called when the architecture exits its oops handler, after printing
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* everything.
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*/
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void oops_exit(void)
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{
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do_oops_enter_exit();
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print_oops_end_marker();
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}
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#ifdef WANT_WARN_ON_SLOWPATH
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void warn_on_slowpath(const char *file, int line)
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{
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char function[KSYM_SYMBOL_LEN];
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unsigned long caller = (unsigned long) __builtin_return_address(0);
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sprint_symbol(function, caller);
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printk(KERN_WARNING "------------[ cut here ]------------\n");
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printk(KERN_WARNING "WARNING: at %s:%d %s()\n", file,
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line, function);
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print_modules();
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dump_stack();
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print_oops_end_marker();
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add_taint(TAINT_WARN);
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}
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EXPORT_SYMBOL(warn_on_slowpath);
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void warn_slowpath(const char *file, int line, const char *fmt, ...)
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{
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va_list args;
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char function[KSYM_SYMBOL_LEN];
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unsigned long caller = (unsigned long)__builtin_return_address(0);
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sprint_symbol(function, caller);
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printk(KERN_WARNING "------------[ cut here ]------------\n");
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printk(KERN_WARNING "WARNING: at %s:%d %s()\n", file,
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line, function);
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va_start(args, fmt);
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vprintk(fmt, args);
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va_end(args);
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print_modules();
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dump_stack();
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print_oops_end_marker();
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add_taint(TAINT_WARN);
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}
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EXPORT_SYMBOL(warn_slowpath);
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#endif
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#ifdef CONFIG_CC_STACKPROTECTOR
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/*
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* Called when gcc's -fstack-protector feature is used, and
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* gcc detects corruption of the on-stack canary value
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*/
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void __stack_chk_fail(void)
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{
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panic("stack-protector: Kernel stack is corrupted");
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}
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EXPORT_SYMBOL(__stack_chk_fail);
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#endif
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