[PATCH] kdump: export per cpu crash notes pointer through sysfs

[linux-drm-fsl-dcu.git] / drivers / base / cpu.c

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 281d26784d251107bc6b158ba3ce5f5904a157fd..982e6583cd633a533fe8a7dbdfe30edc3cbd5437 100644 (file)
--- 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;
 }