1 files changed, 32 insertions, 0 deletions

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 281d26784d25..982e6583cd63 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -83,6 +83,33 @@ static inline void register_cpu_control(struct cpu *cpu)
 }
 #endif /* CONFIG_HOTPLUG_CPU */
 
+#ifdef CONFIG_KEXEC
+#include <linux/kexec.h>
+
+static ssize_t show_crash_notes(struct sys_device *dev, char *buf)
+{
+        struct cpu *cpu = container_of(dev, struct cpu, sysdev);
+        ssize_t rc;
+        unsigned long long addr;
+        int cpunum;
+
+        cpunum = cpu->sysdev.id;
+
+        /*
+         * Might be reading other cpu's data based on which cpu read thread
+         * has been scheduled. But cpu data (memory) is allocated once during
+         * boot up and this data does not change there after. Hence this
+         * operation should be safe. No locking required.
+         */
+        get_cpu();
+        addr = __pa(per_cpu_ptr(crash_notes, cpunum));
+        rc = sprintf(buf, "%Lx\n", addr);
+        put_cpu();
+        return rc;
+}
+static SYSDEV_ATTR(crash_notes, 0400, show_crash_notes, NULL);
+#endif
+
 /*
  * register_cpu - Setup a driverfs device for a CPU.
  * @cpu - Callers can set the cpu->no_control field to 1, to indicate not to
@@ -108,6 +135,11 @@ int __devinit register_cpu(struct cpu *cpu, int num, struct node *root)
                 register_cpu_control(cpu);
         if (!error)
                 cpu_sys_devices[num] = &cpu->sysdev;
+
+#ifdef CONFIG_KEXEC
+        if (!error)
+                error = sysdev_create_file(&cpu->sysdev, &attr_crash_notes);
+#endif
         return error;
 }