linux-kernel - [PATCH 4/5] x86/asm/entry/64: do not GET_THREAD

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 for Android: free password hash cracker in your pocket

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

Message-Id: <1427738975-7391-5-git-send-email-dvlasenk@redhat.com>
Date:	Mon, 30 Mar 2015 20:09:34 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/5] x86/asm/entry/64: do not GET_THREAD_INFO() too early

At exit_intr, we GET_THREAD_INFO(%rcx) and then jump to retint_kernel
if saved CS was from kernel. But code at retint_kernel doesn't need %rcx.

Move GET_THREAD_INFO(%rcx) down, after CS check and branch.

While at it, remove "has a correct top of stack" comment.
After recent changes which eliminated FIXUP_TOP_OF_STACK,
we always have correct pt_regs layout.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Steven Rostedt <rostedt@...dmis.org>
CC: Ingo Molnar <mingo@...nel.org>
CC: Borislav Petkov <bp@...en8.de>
CC: "H. Peter Anvin" <hpa@...or.com>
CC: Andy Lutomirski <luto@...capital.net>
CC: Oleg Nesterov <oleg@...hat.com>
CC: Frederic Weisbecker <fweisbec@...il.com>
CC: Alexei Starovoitov <ast@...mgrid.com>
CC: Will Drewry <wad@...omium.org>
CC: Kees Cook <keescook@...omium.org>
CC: x86@...nel.org
CC: linux-kernel@...r.kernel.org
---
 arch/x86/kernel/entry_64.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 290ecb3..16bf357 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -654,13 +654,12 @@ ret_from_intr:
 	CFI_ADJUST_CFA_OFFSET	RBP
 
 exit_intr:
-	GET_THREAD_INFO(%rcx)
 	testl $3,CS(%rsp)
 	je retint_kernel
-
 	/* Interrupt came from user space */
+
+	GET_THREAD_INFO(%rcx)
 	/*
-	 * Has a correct top of stack.
 	 * %rcx: thread info. Interrupts off.
 	 */
 retint_with_reschedule:
-- 
1.8.1.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/