vmcore: add API to collect hardware dump in second kernel

The sequence of actions done by device drivers to append their device
specific hardware/firmware logs to /proc/vmcore are as follows:

1. During probe (before hardware is initialized), device drivers
register to the vmcore module (via vmcore_add_device_dump()), with
callback function, along with buffer size and log name needed for
firmware/hardware log collection.

2. vmcore module allocates the buffer with requested size. It adds
an Elf note and invokes the device driver's registered callback
function.

3. Device driver collects all hardware/firmware logs into the buffer
and returns control back to vmcore module.

Ensure that the device dump buffer size is always aligned to page size
so that it can be mmaped.

Also, rename alloc_elfnotes_buf() to vmcore_alloc_buf() to make it more
generic and reserve NT_VMCOREDD note type to indicate vmcore device
dump.

Suggested-by: Eric Biederman <ebiederm@xmission.com>.
Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/uapi/linux/vmcore.h b/include/uapi/linux/vmcore.h
new file mode 100644
index 000000000000..022619668e0e
--- /dev/null
+++ b/include/uapi/linux/vmcore.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _UAPI_VMCORE_H
+#define _UAPI_VMCORE_H
+
+#include <linux/types.h>
+
+#define VMCOREDD_NOTE_NAME "LINUX"
+#define VMCOREDD_MAX_NAME_BYTES 44
+
+struct vmcoredd_header {
+	__u32 n_namesz; /* Name size */
+	__u32 n_descsz; /* Content size */
+	__u32 n_type;   /* NT_VMCOREDD */
+	__u8 name[8];   /* LINUX\0\0\0 */
+	__u8 dump_name[VMCOREDD_MAX_NAME_BYTES]; /* Device dump's name */
+};
+
+#endif /* _UAPI_VMCORE_H */