[PATCH 1/2] sysfs: Add crash_notes_size to export percpu note size

[Zhang Yanfei]

For percpu notes, we are exporting only address and not size. So
the userspace tool kexec-tools is putting an upper limit of 1024
and putting the value in p_memsz and p_filesz fields. So the patch
add the new sysfile crash_notes_size to export the exact percpu
note size and let the kexec-tools parse it intead of using 1024.

The idea came from Vivek Goyal. And a later patch will be sent to
kexec-tools to let it parse the size.

Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Signed-off-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
---
 drivers/base/cpu.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index fb10728..a55b590 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -132,6 +132,17 @@ static ssize_t show_crash_notes(struct device *dev, struct device_attribute *att
 	return rc;
 }
 static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
+
+static ssize_t show_crash_notes_size(struct device *dev,
+				     struct device_attribute *attr,
+				     char *buf)
+{
+	ssize_t rc;
+
+	rc = sprintf(buf, "%lu\n", sizeof(note_buf_t));
+	return rc;
+}
+static DEVICE_ATTR(crash_notes_size, 0400, show_crash_notes_size, NULL);
 #endif
 
 /*
@@ -259,6 +270,9 @@ int __cpuinit register_cpu(struct cpu *cpu, int num)
 #ifdef CONFIG_KEXEC
 	if (!error)
 		error = device_create_file(&cpu->dev, &dev_attr_crash_notes);
+	if (!error)
+		error = device_create_file(&cpu->dev,
+					   &dev_attr_crash_notes_size);
 #endif
 	return error;
 }
-- 
1.7.1
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