linux-kernel - [RFC 06/17] x86/asm/64: Use pop instead of movq in syscall_return_via

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: <eb58fad0212a1909924c4988c9d9e526786fb67b.1504733277.git.luto@kernel.org>
Date:   Wed,  6 Sep 2017 14:36:51 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: [RFC 06/17] x86/asm/64: Use pop instead of movq in syscall_return_via_sysret

Saves 64 bytes.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/entry/entry_64.S | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 741b7dc1758b..45d4cb8fd81b 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -308,9 +308,17 @@ return_from_SYSCALL_64:
 	 */
 syscall_return_via_sysret:
 	/* rcx and r11 are already restored (see code above) */
-	RESTORE_EXTRA_REGS
-	RESTORE_C_REGS_EXCEPT_RCX_R11
-	movq	RSP(%rsp), %rsp
+	POP_EXTRA_REGS
+	popq	%rsi	/* skip r11 */
+	popq	%r10
+	popq	%r9
+	popq	%r8
+	popq	%rax
+	popq	%rsi	/* skip rcx */
+	popq	%rdx
+	popq	%rsi
+	popq	%rdi
+	movq	RSP-ORIG_RAX(%rsp), %rsp
 	USERGS_SYSRET64
 END(entry_SYSCALL_64)
 
-- 
2.13.5