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Subject[PATCH 2/4] x86/mce: Get rid of register_mce_write_callback()
Date
From: Borislav Petkov <bp@suse.de>

Make the mcelog call a notifier which lands in the injector module and
does the injection. This allows for mce-inject to be a normal kernel
module now.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/include/asm/mce.h | 4 --
arch/x86/kernel/cpu/mcheck/dev-mcelog.c | 47 +++++++++++++++++-----
arch/x86/kernel/cpu/mcheck/mce-inject.c | 66 +++++++++----------------------
arch/x86/kernel/cpu/mcheck/mce-internal.h | 6 ++-
4 files changed, 61 insertions(+), 62 deletions(-)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 3f9a3d2a5209..181264989db5 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -285,10 +285,6 @@ int mce_notify_irq(void);

DECLARE_PER_CPU(struct mce, injectm);

-extern void register_mce_write_callback(ssize_t (*)(struct file *filp,
- const char __user *ubuf,
- size_t usize, loff_t *off));
-
/* Disable CMCI/polling for MCA bank claimed by firmware */
extern void mce_disable_bank(int bank);

diff --git a/arch/x86/kernel/cpu/mcheck/dev-mcelog.c b/arch/x86/kernel/cpu/mcheck/dev-mcelog.c
index 9c632cb88546..a80427c30c93 100644
--- a/arch/x86/kernel/cpu/mcheck/dev-mcelog.c
+++ b/arch/x86/kernel/cpu/mcheck/dev-mcelog.c
@@ -17,6 +17,8 @@

#include "mce-internal.h"

+static BLOCKING_NOTIFIER_HEAD(mce_injector_chain);
+
static DEFINE_MUTEX(mce_chrdev_read_mutex);

static char mce_helper[128];
@@ -345,24 +347,49 @@ static long mce_chrdev_ioctl(struct file *f, unsigned int cmd,
}
}

-static ssize_t (*mce_write)(struct file *filp, const char __user *ubuf,
- size_t usize, loff_t *off);
+void mce_register_injector_chain(struct notifier_block *nb)
+{
+ blocking_notifier_chain_register(&mce_injector_chain, nb);
+}
+EXPORT_SYMBOL_GPL(mce_register_injector_chain);

-void register_mce_write_callback(ssize_t (*fn)(struct file *filp,
- const char __user *ubuf,
- size_t usize, loff_t *off))
+void mce_unregister_injector_chain(struct notifier_block *nb)
{
- mce_write = fn;
+ blocking_notifier_chain_unregister(&mce_injector_chain, nb);
}
-EXPORT_SYMBOL_GPL(register_mce_write_callback);
+EXPORT_SYMBOL_GPL(mce_unregister_injector_chain);

static ssize_t mce_chrdev_write(struct file *filp, const char __user *ubuf,
size_t usize, loff_t *off)
{
- if (mce_write)
- return mce_write(filp, ubuf, usize, off);
- else
+ struct mce m;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ /*
+ * There are some cases where real MSR reads could slip
+ * through.
+ */
+ if (!boot_cpu_has(X86_FEATURE_MCE) || !boot_cpu_has(X86_FEATURE_MCA))
+ return -EIO;
+
+ if ((unsigned long)usize > sizeof(struct mce))
+ usize = sizeof(struct mce);
+ if (copy_from_user(&m, ubuf, usize))
+ return -EFAULT;
+
+ if (m.extcpu >= num_possible_cpus() || !cpu_online(m.extcpu))
return -EINVAL;
+
+ /*
+ * Need to give user space some time to set everything up,
+ * so do it a jiffie or two later everywhere.
+ */
+ schedule_timeout(2);
+
+ blocking_notifier_call_chain(&mce_injector_chain, 0, &m);
+
+ return usize;
}

static const struct file_operations mce_chrdev_ops = {
diff --git a/arch/x86/kernel/cpu/mcheck/mce-inject.c b/arch/x86/kernel/cpu/mcheck/mce-inject.c
index 45b81c84ed1e..354e83582006 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-inject.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-inject.c
@@ -283,42 +283,24 @@ static void __maybe_unused raise_mce(struct mce *m)
}
}

-#ifdef CONFIG_X86_MCELOG_LEGACY
-/* Error injection interface */
-static ssize_t mce_write(struct file *filp, const char __user *ubuf,
- size_t usize, loff_t *off)
+static int mce_inject_raise(struct notifier_block *nb, unsigned long val,
+ void *data)
{
- struct mce m;
-
- if (!capable(CAP_SYS_ADMIN))
- return -EPERM;
- /*
- * There are some cases where real MSR reads could slip
- * through.
- */
- if (!boot_cpu_has(X86_FEATURE_MCE) || !boot_cpu_has(X86_FEATURE_MCA))
- return -EIO;
-
- if ((unsigned long)usize > sizeof(struct mce))
- usize = sizeof(struct mce);
- if (copy_from_user(&m, ubuf, usize))
- return -EFAULT;
-
- if (m.extcpu >= num_possible_cpus() || !cpu_online(m.extcpu))
- return -EINVAL;
+ struct mce *m = (struct mce *)data;

- /*
- * Need to give user space some time to set everything up,
- * so do it a jiffie or two later everywhere.
- */
- schedule_timeout(2);
+ if (!m)
+ return NOTIFY_DONE;

mutex_lock(&mce_inject_mutex);
- raise_mce(&m);
+ raise_mce(m);
mutex_unlock(&mce_inject_mutex);
- return usize;
+
+ return NOTIFY_DONE;
}
-#endif /* CONFIG_X86_MCELOG_LEGACY */
+
+static struct notifier_block inject_nb = {
+ .notifier_call = mce_inject_raise,
+};

/*
* Caller needs to be make sure this cpu doesn't disappear
@@ -719,44 +701,34 @@ static int inject_init(void)
if (!alloc_cpumask_var(&mce_inject_cpumask, GFP_KERNEL))
return -ENOMEM;

-#ifdef CONFIG_X86_MCELOG_LEGACY
- register_mce_write_callback(mce_write);
-#endif
-
- register_nmi_handler(NMI_LOCAL, mce_raise_notify, 0, "mce_notify");
-
err = debugfs_init();
if (err) {
free_cpumask_var(mce_inject_cpumask);
return err;
}

+ register_nmi_handler(NMI_LOCAL, mce_raise_notify, 0, "mce_notify");
+ mce_register_injector_chain(&inject_nb);
+
pr_info("Machine check injector initialized\n");

return 0;
}

-module_init(inject_init);
-
-/*
- * Cannot tolerate unloading currently because we cannot
- * guarantee all openers of mce_chrdev will get a reference to us.
- */
-#ifndef CONFIG_X86_MCELOG_LEGACY
static void __exit inject_exit(void)
{

+ mce_unregister_injector_chain(&inject_nb);
+ unregister_nmi_handler(NMI_LOCAL, "mce_notify");
+
debugfs_remove_recursive(dfs_inj);
dfs_inj = NULL;

memset(&dfs_fls, 0, sizeof(dfs_fls));

- unregister_nmi_handler(NMI_LOCAL, "mce_notify");
-
free_cpumask_var(mce_inject_cpumask);
}

+module_init(inject_init);
module_exit(inject_exit);
-#endif
-
MODULE_LICENSE("GPL");
diff --git a/arch/x86/kernel/cpu/mcheck/mce-internal.h b/arch/x86/kernel/cpu/mcheck/mce-internal.h
index 654ad0668d72..098530a93bb7 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-internal.h
+++ b/arch/x86/kernel/cpu/mcheck/mce-internal.h
@@ -100,7 +100,11 @@ static inline bool mce_cmp(struct mce *m1, struct mce *m2)
extern struct device_attribute dev_attr_trigger;

#ifdef CONFIG_X86_MCELOG_LEGACY
-extern void mce_work_trigger(void);
+void mce_work_trigger(void);
+void mce_register_injector_chain(struct notifier_block *nb);
+void mce_unregister_injector_chain(struct notifier_block *nb);
#else
static inline void mce_work_trigger(void) { }
+static inline void mce_register_injector_chain(struct notifier_block *nb) { }
+static inline void mce_unregister_injector_chain(struct notifier_block *nb) { }
#endif
--
2.13.0
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