linux-kernel - [PATCH] dmi: Feed DMI table to /dev/random driver

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Date:	Fri, 20 Jul 2012 13:15:20 -0700
From:	Tony Luck <tony.luck@...el.com>
To:	Theodore Ts'o <tytso@....edu>
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	w@....eu, ewust@...ch.edu, zakir@...ch.edu, greg@...ah.com,
	mpm@...enic.com, nadiah@...ucsd.edu, jhalderm@...ch.edu,
	tglx@...utronix.de, davem@...emloft.net,
	Theodore Ts'o <tytso@....edu>
Subject: [PATCH] dmi: Feed DMI table to /dev/random driver

Send the entire DMI (SMBIOS) table to the /dev/random driver to
help seed its pools.

Signed-off-by: Tony Luck <tony.luck@...el.com>
---

This looks a useful addition to your /dev/random series. There are
lots of platform specific goodies in this table (BIOS version, system
serial number and UUID, count and version number of processors, DIMM
slot population and serial numbers, etc.)

On the system I tested the patch on the table is 9866 bytes. Is it
OK to dump that much into add_device_randomness() in one shot? The
alternative is to select the 'useful' bits deeper into the routines
that parse the entries in the table.

 drivers/firmware/dmi_scan.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 153980b..b298158 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -6,6 +6,7 @@
 #include <linux/dmi.h>
 #include <linux/efi.h>
 #include <linux/bootmem.h>
+#include <linux/random.h>
 #include <asm/dmi.h>
 
 /*
@@ -111,6 +112,8 @@ static int __init dmi_walk_early(void (*decode)(const struct dmi_header *,
 
 	dmi_table(buf, dmi_len, dmi_num, decode, NULL);
 
+	add_device_randomness(buf, dmi_len);
+
 	dmi_iounmap(buf, dmi_len);
 	return 0;
 }
-- 
1.7.10.2.552.gaa3bb87

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