linux-kernel - [PATCH 4/8] random: remove unused branch in hot code path

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <3380804.uZWydldqLU@positron.chronox.de>
Date:   Tue, 27 Dec 2016 23:40:23 +0100
From:   Stephan Müller <smueller@...onox.de>
To:     Ted Tso <tytso@....edu>
Cc:     linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: [PATCH 4/8] random: remove unused branch in hot code path

The variable ip is defined to be a __u64 which is always 8 bytes on any
architecture. Thus, the check for sizeof(ip) > 4 will always be true.

As the check happens in a hot code path, remove the branch.

Signed-off-by: Stephan Mueller <smueller@...onox.de>
---
 drivers/char/random.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 5c26b1c..8d4d720 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1136,8 +1136,7 @@ void add_interrupt_randomness(int irq, int irq_flags)
 	fast_pool->pool[1] ^= now ^ c_high;
 	ip = regs ? instruction_pointer(regs) : _RET_IP_;
 	fast_pool->pool[2] ^= ip;
-	fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
-		get_reg(fast_pool, regs);
+	fast_pool->pool[3] ^= ip >> 32;
 
 	fast_mix(fast_pool);
 	add_interrupt_bench(cycles);
-- 
2.9.3