Re: [PATCH v2 x86 1/2] fix page faults by nmiaction in nmi if kmemcheck is enabled

Don Zickus
2012-03-05T15:55:54Z

On Mon, Mar 05, 2012 at 06:05:17PM +0800, Li Zhong wrote:
> This patch tries to fix the problem of page fault exception caused by
> accessing nmiaction structure in nmi if kmemcheck is enabled.
>
> If kmemcheck is enabled, the memory allocated through slab are in pages
> that are marked non-present, so that some checks could be done in the
> page fault handling code ( e.g. whether the memory is read before
> written to ).
> As nmiaction is allocated in this way, so it resides in a non-present
> page. Then there is a page fault while the nmi code accessing the
> nmiaction structure, which would then cause a warning by
> WARN_ON_ONCE(in_nmi()) in kmemcheck_fault(), called by do_page_fault().

This is one way of doing this. I was trying to avoid this when I rewrote the
nmi handlers, because everyone kept screwing up the structs. I thought it
would be safer to have callers pass in data based on an api instead.

So I am not necessarily a big fan of this patch (nor is it entirely
correct because you throwaway all the checks in register_nmi_handler()).

Then again I am not a memory expert and may be misunderstanding something
simple why it is safer to do static storage.

Cheers,
Don

>
> v2: as Peter suggested, changed the nmiaction to use static storage.
>
> Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
> ---
> arch/x86/include/asm/nmi.h | 10 +++++-
> arch/x86/kernel/apic/hw_nmi.c | 8 ++++-
> arch/x86/kernel/apic/x2apic_uv_x.c | 7 ++++-
> arch/x86/kernel/cpu/mcheck/mce-inject.c | 8 ++++-
> arch/x86/kernel/cpu/perf_event.c | 7 ++++-
> arch/x86/kernel/kgdb.c | 11 ++++--
> arch/x86/kernel/nmi.c | 49 ++----------------------------
> arch/x86/kernel/nmi_selftest.c | 16 ++++++++--
> arch/x86/kernel/reboot.c | 9 ++++-
> arch/x86/kernel/smp.c | 9 ++++-
> arch/x86/oprofile/nmi_int.c | 8 ++++-
> drivers/acpi/apei/ghes.c | 8 ++++-
> drivers/char/ipmi/ipmi_watchdog.c | 10 +++++-
> drivers/watchdog/hpwdt.c | 21 +++++++++++--
> 14 files changed, 108 insertions(+), 73 deletions(-)
>
> diff --git a/arch/x86/include/asm/nmi.h b/arch/x86/include/asm/nmi.h
> index fd3f9f1..08d464f 100644
> --- a/arch/x86/include/asm/nmi.h
> +++ b/arch/x86/include/asm/nmi.h
> @@ -35,8 +35,14 @@ enum {
>
> typedef int (*nmi_handler_t)(unsigned int, struct pt_regs *);
>
> -int register_nmi_handler(unsigned int, nmi_handler_t, unsigned long,
> - const char *);
> +struct nmiaction {
> + struct list_head list;
> + nmi_handler_t handler;
> + unsigned int flags;
> + const char *name;
> +};
> +
> +int register_nmi_handler(unsigned int, struct nmiaction *);
>
> void unregister_nmi_handler(unsigned int, const char *);
>
> diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
> index 31cb9ae..9baea77 100644
> --- a/arch/x86/kernel/apic/hw_nmi.c
> +++ b/arch/x86/kernel/apic/hw_nmi.c
> @@ -80,10 +80,14 @@ arch_trigger_all_cpu_backtrace_handler(unsigned int cmd, struct pt_regs *regs)
> return NMI_DONE;
> }
>
> +static struct nmiaction arch_trigger_all_cpu_bt_nmiaction = {
> + .handler = arch_trigger_all_cpu_backtrace_handler,
> + .name = "arch_bt",
> +};
> +
> static int __init register_trigger_all_cpu_backtrace(void)
> {
> - register_nmi_handler(NMI_LOCAL, arch_trigger_all_cpu_backtrace_handler,
> - 0, "arch_bt");
> + register_nmi_handler(NMI_LOCAL, &arch_trigger_all_cpu_bt_nmiaction);
> return 0;
> }
> early_initcall(register_trigger_all_cpu_backtrace);
> diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
> index 79b05b8..5739042 100644
> --- a/arch/x86/kernel/apic/x2apic_uv_x.c
> +++ b/arch/x86/kernel/apic/x2apic_uv_x.c
> @@ -715,9 +715,14 @@ int uv_handle_nmi(unsigned int reason, struct pt_regs *regs)
> return NMI_HANDLED;
> }
>
> +static struct nmiaction uv_nmiaction = {
> + .handler = uv_handle_nmi,
> + .name = "uv",
> +};
> +
> void uv_register_nmi_notifier(void)
> {
> - if (register_nmi_handler(NMI_UNKNOWN, uv_handle_nmi, 0, "uv"))
> + if (register_nmi_handler(NMI_UNKNOWN, &uv_nmiaction))
> printk(KERN_WARNING "UV NMI handler failed to register\n");
> }
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce-inject.c b/arch/x86/kernel/cpu/mcheck/mce-inject.c
> index fc4beb3..f9ab41c 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce-inject.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce-inject.c
> @@ -229,14 +229,18 @@ static ssize_t mce_write(struct file *filp, const char __user *ubuf,
> return usize;
> }
>
> +static struct nmiaction mce_nmiaction = {
> + .handler = mce_raise_notify,
> + .name = "mce_notify",
> +};
> +
> static int inject_init(void)
> {
> if (!alloc_cpumask_var(&mce_inject_cpumask, GFP_KERNEL))
> return -ENOMEM;
> printk(KERN_INFO "Machine check injector initialized\n");
> register_mce_write_callback(mce_write);
> - register_nmi_handler(NMI_LOCAL, mce_raise_notify, 0,
> - "mce_notify");
> + register_nmi_handler(NMI_LOCAL, &mce_nmiaction);
> return 0;
> }
>
> diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
> index 5adce10..8bdff1b 100644
> --- a/arch/x86/kernel/cpu/perf_event.c
> +++ b/arch/x86/kernel/cpu/perf_event.c
> @@ -1246,6 +1246,11 @@ static void __init pmu_check_apic(void)
> pr_info("no hardware sampling interrupt available.\n");
> }
>
> +static struct nmiaction perf_event_nmiaction = {
> + .handler = perf_event_nmi_handler,
> + .name = "PMI",
> +};
> +
> static int __init init_hw_perf_events(void)
> {
> struct x86_pmu_quirk *quirk;
> @@ -1297,7 +1302,7 @@ static int __init init_hw_perf_events(void)
> ((1LL << x86_pmu.num_counters_fixed)-1) << X86_PMC_IDX_FIXED;
>
> perf_events_lapic_init();
> - register_nmi_handler(NMI_LOCAL, perf_event_nmi_handler, 0, "PMI");
> + register_nmi_handler(NMI_LOCAL, &perf_event_nmiaction);
>
> unconstrained = (struct event_constraint)
> __EVENT_CONSTRAINT(0, (1ULL << x86_pmu.num_counters) - 1,
> diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
> index faba577..d259d2a 100644
> --- a/arch/x86/kernel/kgdb.c
> +++ b/arch/x86/kernel/kgdb.c
> @@ -601,6 +601,11 @@ static struct notifier_block kgdb_notifier = {
> .notifier_call = kgdb_notify,
> };
>
> +static struct nmiaction kgdb_nmiaction = {
> + .handler = kgdb_nmi_handler,
> + .name = "kgdb",
> +};
> +
> /**
> * kgdb_arch_init - Perform any architecture specific initalization.
> *
> @@ -615,13 +620,11 @@ int kgdb_arch_init(void)
> if (retval)
> goto out;
>
> - retval = register_nmi_handler(NMI_LOCAL, kgdb_nmi_handler,
> - 0, "kgdb");
> + retval = register_nmi_handler(NMI_LOCAL, &kgdb_nmiaction);
> if (retval)
> goto out1;
>
> - retval = register_nmi_handler(NMI_UNKNOWN, kgdb_nmi_handler,
> - 0, "kgdb");
> + retval = register_nmi_handler(NMI_UNKNOWN, &kgdb_nmiaction);
>
> if (retval)
> goto out2;
> diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
> index 47acaf3..d844acc 100644
> --- a/arch/x86/kernel/nmi.c
> +++ b/arch/x86/kernel/nmi.c
> @@ -31,14 +31,6 @@
> #include <asm/nmi.h>
> #include <asm/x86_init.h>
>
> -#define NMI_MAX_NAMELEN 16
> -struct nmiaction {
> - struct list_head list;
> - nmi_handler_t handler;
> - unsigned int flags;
> - char *name;
> -};
> -
> struct nmi_desc {
> spinlock_t lock;
> struct list_head head;
> @@ -160,51 +152,18 @@ static struct nmiaction *__free_nmi(unsigned int type, const char *name)
> return (n);
> }
>
> -int register_nmi_handler(unsigned int type, nmi_handler_t handler,
> - unsigned long nmiflags, const char *devname)
> +int register_nmi_handler(unsigned int type, struct nmiaction *na)
> {
> - struct nmiaction *action;
> - int retval = -ENOMEM;
> -
> - if (!handler)
> + if (!na->handler)
> return -EINVAL;
>
> - action = kzalloc(sizeof(struct nmiaction), GFP_KERNEL);
> - if (!action)
> - goto fail_action;
> -
> - action->handler = handler;
> - action->flags = nmiflags;
> - action->name = kstrndup(devname, NMI_MAX_NAMELEN, GFP_KERNEL);
> - if (!action->name)
> - goto fail_action_name;
> -
> - retval = __setup_nmi(type, action);
> -
> - if (retval)
> - goto fail_setup_nmi;
> -
> - return retval;
> -
> -fail_setup_nmi:
> - kfree(action->name);
> -fail_action_name:
> - kfree(action);
> -fail_action:
> -
> - return retval;
> + return __setup_nmi(type, na);
> }
> EXPORT_SYMBOL_GPL(register_nmi_handler);
>
> void unregister_nmi_handler(unsigned int type, const char *name)
> {
> - struct nmiaction *a;
> -
> - a = __free_nmi(type, name);
> - if (a) {
> - kfree(a->name);
> - kfree(a);
> - }
> + __free_nmi(type, name);
> }
>
> EXPORT_SYMBOL_GPL(unregister_nmi_handler);
> diff --git a/arch/x86/kernel/nmi_selftest.c b/arch/x86/kernel/nmi_selftest.c
> index 0d01a8e..40fd637 100644
> --- a/arch/x86/kernel/nmi_selftest.c
> +++ b/arch/x86/kernel/nmi_selftest.c
> @@ -37,10 +37,15 @@ static int nmi_unk_cb(unsigned int val, struct pt_regs *regs)
> return NMI_HANDLED;
> }
>
> +static struct nmiaction selftest_unk_nmiaction = {
> + .handler = nmi_unk_cb,
> + .name = "nmi_selftest_unk",
> +};
> +
> static void init_nmi_testsuite(void)
> {
> /* trap all the unknown NMIs we may generate */
> - register_nmi_handler(NMI_UNKNOWN, nmi_unk_cb, 0, "nmi_selftest_unk");
> + register_nmi_handler(NMI_UNKNOWN, &selftest_unk_nmiaction);
> }
>
> static void cleanup_nmi_testsuite(void)
> @@ -58,12 +63,17 @@ static int test_nmi_ipi_callback(unsigned int val, struct pt_regs *regs)
> return NMI_DONE;
> }
>
> +static struct nmiaction selftest_nmiaction = {
> + .handler = test_nmi_ipi_callback,
> + .flags = NMI_FLAG_FIRST,
> + .name = "nmi_selftest",
> +};
> +
> static void test_nmi_ipi(struct cpumask *mask)
> {
> unsigned long timeout;
>
> - if (register_nmi_handler(NMI_LOCAL, test_nmi_ipi_callback,
> - NMI_FLAG_FIRST, "nmi_selftest")) {
> + if (register_nmi_handler(NMI_LOCAL, &selftest_nmiaction)) {
> nmi_fail = FAILURE;
> return;
> }
> diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
> index d840e69..a0f8c15 100644
> --- a/arch/x86/kernel/reboot.c
> +++ b/arch/x86/kernel/reboot.c
> @@ -799,6 +799,12 @@ static void smp_send_nmi_allbutself(void)
> apic->send_IPI_allbutself(NMI_VECTOR);
> }
>
> +static struct nmiaction crash_nmiaction = {
> + .handler = crash_nmi_callback,
> + .flags = NMI_FLAG_FIRST,
> + .name = "crash",
> +};
> +
> /* Halt all other CPUs, calling the specified function on each of them
> *
> * This function can be used to halt all other CPUs on crash
> @@ -817,8 +823,7 @@ void nmi_shootdown_cpus(nmi_shootdown_cb callback)
>
> atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
> /* Would it be better to replace the trap vector here? */
> - if (register_nmi_handler(NMI_LOCAL, crash_nmi_callback,
> - NMI_FLAG_FIRST, "crash"))
> + if (register_nmi_handler(NMI_LOCAL, &crash_nmiaction))
> return; /* return what? */
> /* Ensure the new callback function is set before sending
> * out the NMI
> diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
> index 66c74f4..135d0b2 100644
> --- a/arch/x86/kernel/smp.c
> +++ b/arch/x86/kernel/smp.c
> @@ -162,6 +162,12 @@ static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
> return NMI_HANDLED;
> }
>
> +static struct nmiaction smp_stop_nmiaction = {
> + .handler = smp_stop_nmi_callback,
> + .flags = NMI_FLAG_FIRST,
> + .name = "smp_stop",
> +};
> +
> static void native_nmi_stop_other_cpus(int wait)
> {
> unsigned long flags;
> @@ -179,8 +185,7 @@ static void native_nmi_stop_other_cpus(int wait)
> if (atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id()) != -1)
> return;
>
> - if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
> - NMI_FLAG_FIRST, "smp_stop"))
> + if (register_nmi_handler(NMI_LOCAL, &smp_stop_nmiaction))
> /* Note: we ignore failures here */
> return;
>
> diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c
> index 26b8a85..c3408f6 100644
> --- a/arch/x86/oprofile/nmi_int.c
> +++ b/arch/x86/oprofile/nmi_int.c
> @@ -453,6 +453,11 @@ static struct notifier_block oprofile_cpu_nb = {
> .notifier_call = oprofile_cpu_notifier
> };
>
> +static struct nmiaction oprofile_nmiaction = {
> + .handler = profile_exceptions_notify,
> + .name = "oprofile",
> +};
> +
> static int nmi_setup(void)
> {
> int err = 0;
> @@ -489,8 +494,7 @@ static int nmi_setup(void)
> ctr_running = 0;
> /* make variables visible to the nmi handler: */
> smp_mb();
> - err = register_nmi_handler(NMI_LOCAL, profile_exceptions_notify,
> - 0, "oprofile");
> + err = register_nmi_handler(NMI_LOCAL, &oprofile_nmiaction);
> if (err)
> goto fail;
>
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index 9b3cac0..1d38f92 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -901,6 +901,11 @@ static unsigned long ghes_esource_prealloc_size(
> return prealloc_size;
> }
>
> +static struct nmiaction ghes_nmiaction = {
> + .handler = ghes_notify_nmi,
> + .name = "ghes",
> +};
> +
> static int __devinit ghes_probe(struct platform_device *ghes_dev)
> {
> struct acpi_hest_generic *generic;
> @@ -975,8 +980,7 @@ static int __devinit ghes_probe(struct platform_device *ghes_dev)
> ghes_estatus_pool_expand(len);
> mutex_lock(&ghes_list_mutex);
> if (list_empty(&ghes_nmi))
> - register_nmi_handler(NMI_LOCAL, ghes_notify_nmi, 0,
> - "ghes");
> + register_nmi_handler(NMI_LOCAL, &ghes_nmiaction);
> list_add_rcu(&ghes->list, &ghes_nmi);
> mutex_unlock(&ghes_list_mutex);
> break;
> diff --git a/drivers/char/ipmi/ipmi_watchdog.c b/drivers/char/ipmi/ipmi_watchdog.c
> index 34767a6..29a6e0a 100644
> --- a/drivers/char/ipmi/ipmi_watchdog.c
> +++ b/drivers/char/ipmi/ipmi_watchdog.c
> @@ -1296,6 +1296,13 @@ static int preop_op(const char *inval, char *outval)
> return 0;
> }
>
> +#ifdef HAVE_DIE_NMI
> +static struct nmiaction ipmi_nmiaction = {
> + .handler = ipmi_nmi,
> + .name = "ipmi",
> +};
> +#endif
> +
> static void check_parms(void)
> {
> #ifdef HAVE_DIE_NMI
> @@ -1313,8 +1320,7 @@ static void check_parms(void)
> }
> }
> if (do_nmi && !nmi_handler_registered) {
> - rv = register_nmi_handler(NMI_UNKNOWN, ipmi_nmi, 0,
> - "ipmi");
> + rv = register_nmi_handler(NMI_UNKNOWN, &ipmi_nmiaction);
> if (rv) {
> printk(KERN_WARNING PFX
> "Can't register nmi handler\n");
> diff --git a/drivers/watchdog/hpwdt.c b/drivers/watchdog/hpwdt.c
> index 8464ea1..e575e63 100644
> --- a/drivers/watchdog/hpwdt.c
> +++ b/drivers/watchdog/hpwdt.c
> @@ -689,9 +689,22 @@ static void __devinit dmi_find_icru(const struct dmi_header *dm, void *dummy)
> }
> }
>
> +static struct nmiaction hpwdt_nmiaction[] = {
> + {
> + .handler = hpwdt_pretimeout,
> + .name = "hpwdt",
> + },
> + {
> + .handler = hpwdt_pretimeout,
> + .flags = NMI_FLAG_FIRST,
> + .name = "hpwdt",
> + },
> +};
> +
> static int __devinit hpwdt_init_nmi_decoding(struct pci_dev *dev)
> {
> int retval;
> + struct nmiaction *na = hpwdt_nmiaction;
>
> /*
> * On typical CRU-based systems we need to map that service in
> @@ -733,9 +746,11 @@ static int __devinit hpwdt_init_nmi_decoding(struct pci_dev *dev)
> * die notify list to handle a critical NMI. The default is to
> * be last so other users of the NMI signal can function.
> */
> - retval = register_nmi_handler(NMI_UNKNOWN, hpwdt_pretimeout,
> - (priority) ? NMI_FLAG_FIRST : 0,
> - "hpwdt");
> +
> + if (priority)
> + na = &hpwdt_nmiaction[1];
> +
> + retval = register_nmi_handler(NMI_UNKNOWN, na);
> if (retval != 0) {
> dev_warn(&dev->dev,
> "Unable to register a die notifier (err=%d).\n",
> --
> 1.7.1
>
>
>
>