/* * linux/arch/i386/nmi.c * * NMI watchdog support on APIC systems * * Started by Ingo Molnar * * Fixes: * Mikael Pettersson : AMD K7 support for local APIC NMI watchdog. * Mikael Pettersson : Power Management for local APIC NMI watchdog. * Mikael Pettersson : Pentium 4 support for local APIC NMI watchdog. * Pavel Machek and * Mikael Pettersson : PM converted to driver model. Disable/enable API. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include unsigned int nmi_watchdog = NMI_NONE; static unsigned int nmi_hz = HZ; static unsigned int nmi_perfctr_msr; /* the MSR to reset in NMI handler */ static unsigned int nmi_p4_cccr_val; static DEFINE_PER_CPU(struct timer, nmi_timer); static DEFINE_PER_CPU(unsigned int, nmi_timer_ticks); /* * lapic_nmi_owner tracks the ownership of the lapic NMI hardware: * - it may be reserved by some other driver, or not * - when not reserved by some other driver, it may be used for * the NMI watchdog, or not * * This is maintained separately from nmi_active because the NMI * watchdog may also be driven from the I/O APIC timer. */ static DEFINE_SPINLOCK(lapic_nmi_owner_lock); static unsigned int lapic_nmi_owner; #define LAPIC_NMI_WATCHDOG (1<<0) #define LAPIC_NMI_RESERVED (1<<1) /* nmi_active: * +1: the lapic NMI watchdog is active, but can be disabled * 0: the lapic NMI watchdog has not been set up, and cannot * be enabled * -1: the lapic NMI watchdog is disabled, but can be enabled */ int nmi_active; #define K7_EVNTSEL_ENABLE (1 << 22) #define K7_EVNTSEL_INT (1 << 20) #define K7_EVNTSEL_OS (1 << 17) #define K7_EVNTSEL_USR (1 << 16) #define K7_EVENT_CYCLES_PROCESSOR_IS_RUNNING 0x76 #define K7_NMI_EVENT K7_EVENT_CYCLES_PROCESSOR_IS_RUNNING #define P6_EVNTSEL0_ENABLE (1 << 22) #define P6_EVNTSEL_INT (1 << 20) #define P6_EVNTSEL_OS (1 << 17) #define P6_EVNTSEL_USR (1 << 16) #define P6_EVENT_CPU_CLOCKS_NOT_HALTED 0x79 #define P6_NMI_EVENT P6_EVENT_CPU_CLOCKS_NOT_HALTED #define P4_ESCR_EVENT_SELECT(N) ((N)<<25) #define P4_CCCR_OVF_PMI0 (1<<26) #define P4_CCCR_OVF_PMI1 (1<<27) #define P4_CCCR_THRESHOLD(N) ((N)<<20) #define P4_CCCR_COMPLEMENT (1<<19) #define P4_CCCR_COMPARE (1<<18) #define P4_CCCR_REQUIRED (3<<16) #define P4_CCCR_ESCR_SELECT(N) ((N)<<13) #define P4_CCCR_ENABLE (1<<12) /* * Set up IQ_PERFCTR0 to behave like a clock, by having IQ_CCCR0 filter * CRU_ESCR0 (with any non-null event selector) through a complemented * max threshold. [IA32-Vol3, Section 14.9.9] */ #define P4_NMI_CRU_ESCR0 P4_ESCR_EVENT_SELECT(0x3F) #define P4_NMI_IQ_CCCR0 \ (P4_CCCR_OVF_PMI0|P4_CCCR_THRESHOLD(15)|P4_CCCR_COMPLEMENT| \ P4_CCCR_COMPARE|P4_CCCR_REQUIRED|P4_CCCR_ESCR_SELECT(4)|P4_CCCR_ENABLE) int __init check_nmi_watchdog (void) { unsigned int prev_nmi_count[NR_CPUS]; int cpu; if ( !nmi_watchdog ) return 0; printk("Testing NMI watchdog --- "); for ( cpu = 0; cpu < NR_CPUS; cpu++ ) prev_nmi_count[cpu] = nmi_count(cpu); local_irq_enable(); mdelay((10*1000)/nmi_hz); /* wait 10 ticks */ for ( cpu = 0; cpu < NR_CPUS; cpu++ ) { if ( !cpu_isset(cpu, cpu_callin_map) && !cpu_isset(cpu, cpu_online_map) ) continue; if ( nmi_count(cpu) - prev_nmi_count[cpu] <= 5 ) printk("CPU#%d stuck. ", cpu); else printk("CPU#%d okay. ", cpu); } printk("\n"); /* now that we know it works we can reduce NMI frequency to something more reasonable; makes a difference in some configs */ if ( nmi_watchdog == NMI_LOCAL_APIC ) nmi_hz = 1; return 0; } static void nmi_timer_fn(void *unused) { this_cpu(nmi_timer_ticks)++; set_timer(&this_cpu(nmi_timer), NOW() + MILLISECS(1000)); } static void disable_lapic_nmi_watchdog(void) { if (nmi_active <= 0) return; switch (boot_cpu_data.x86_vendor) { case X86_VENDOR_AMD: wrmsr(MSR_K7_EVNTSEL0, 0, 0); break; case X86_VENDOR_INTEL: switch (boot_cpu_data.x86) { case 6: if (boot_cpu_data.x86_model > 0xd) break; wrmsr(MSR_P6_EVNTSEL0, 0, 0); break; case 15: if (boot_cpu_data.x86_model > 0x4) break; wrmsr(MSR_P4_IQ_CCCR0, 0, 0); wrmsr(MSR_P4_CRU_ESCR0, 0, 0); break; } break; } nmi_active = -1; /* tell do_nmi() and others that we're not active any more */ nmi_watchdog = 0; } static void enable_lapic_nmi_watchdog(void) { if (nmi_active < 0) { nmi_watchdog = NMI_LOCAL_APIC; setup_apic_nmi_watchdog(); } } int reserve_lapic_nmi(void) { unsigned int old_owner; spin_lock(&lapic_nmi_owner_lock); old_owner = lapic_nmi_owner; lapic_nmi_owner |= LAPIC_NMI_RESERVED; spin_unlock(&lapic_nmi_owner_lock); if (old_owner & LAPIC_NMI_
My local cafe is serviced by a rickety and unreliable wireless network,
generously sponsored with ratepayers' money by our city council. After
connecting, you  are redirected to an SSL-protected page that prompts you for a
username and password. Once you've entered your details, you are free to enjoy
the intermittent dropouts, treacle-like speeds and incorrectly configured
transparent proxy. 

I tend to automate this kind of thing at the first opportunity, on the theory
that time spent now will be more than made up in the long run. In this case, I
might use [Firebug](http://getfirebug.com/) to ferret out the form post
parameters and target URL, then fire up an editor to write a little script
using Python's [urllib](http://docs.python.org/library/urllib.html) to simulate
a submission. That's a lot of futzing about. With mitmproxy we can do the job
in literally 30 seconds, without having to worry about any of the details.
Here's how.

## 1. Run mitmdump to record our HTTP conversation to a file.

<pre class="terminal">
> mitmdump -w wireless-login
</pre>

## 2. Point your browser at the mitmdump instance. 

I use a tiny Firefox addon called [Toggle
Proxy](https://addons.mozilla.org/en-us/firefox/addon/toggle-proxy-51740/) to
switch quickly to and from mitmproxy. I'm assuming you've already [configured
your browser with mitmproxy's SSL certificate
authority](http://mitmproxy.org/doc/ssl.html).

## 3. Log in as usual. 


And that's it! You now have a serialized version of the login process in the
file wireless-login, and you can replay it at any time like this:

<pre class="terminal">
> mitmdump -c wireless-login
</pre>

## Embellishments

We're really done at this point, but there are a couple of embellishments we
could make if we wanted. I use [wicd](http://wicd.sourceforge.net/) to
automatically join wireless networks I frequent, and it lets me specify a
command to run after connecting. I used the client replay command above and
voila! - totally hands-free wireless network startup.

We might also want to prune requests that download CSS, JS, images and so
forth. These add only a few moments to the time it takes to replay, but they're
not really needed and I somehow feel compelled to trim them anyway. So, we fire up
the mitmproxy console tool on our serialized conversation, like so:

<pre class="terminal">
> mitmproxy -r wireless-login
</pre>

We can now go through and manually delete (using the __d__ keyboard shortcut)
everything we want to trim. When we're done, we use __w__ to save the
conversation back to the file.
generated by cgit v1.2.3 (git 2.25.1) at 2026-02-06 07:01:34 +0000