From: "H. Peter Anvin" <hpa@zytor.com>
To: Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [RFC PATCH 4/6] x86/syscall: maximize MSR_SYSCALL_MASK
Date: Mon, 10 May 2021 10:45:07 -0700 [thread overview]
Message-ID: <20210510174509.3039991-5-hpa@zytor.com> (raw)
In-Reply-To: <20210510174509.3039991-1-hpa@zytor.com>
From: "H. Peter Anvin (Intel)" <hpa@zytor.com>
It is better to clear as many flags as possible when we do a system
call entry, as opposed to the other way around. The fewer flags we
keep, the lesser the possible interference between the kernel and user
space.
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
---
arch/x86/kernel/cpu/common.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a1b756c49a93..6cf697574661 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1773,10 +1773,16 @@ void syscall_init(void)
wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL);
#endif
- /* Flags to clear on syscall */
+ /*
+ * Flags to clear on syscall; clear as much as possible
+ * to minimize user space-kernel interference.
+ */
wrmsrl(MSR_SYSCALL_MASK,
- X86_EFLAGS_TF|X86_EFLAGS_DF|X86_EFLAGS_IF|
- X86_EFLAGS_IOPL|X86_EFLAGS_AC|X86_EFLAGS_NT);
+ X86_EFLAGS_CF|X86_EFLAGS_PF|X86_EFLAGS_AF|
+ X86_EFLAGS_ZF|X86_EFLAGS_SF|X86_EFLAGS_TF|
+ X86_EFLAGS_IF|X86_EFLAGS_DF|X86_EFLAGS_OF|
+ X86_EFLAGS_IOPL|X86_EFLAGS_NT|X86_EFLAGS_RF|
+ X86_EFLAGS_AC|X86_EFLAGS_ID);
}
#else /* CONFIG_X86_64 */
--
2.31.1
next prev parent reply other threads:[~2021-05-10 17:45 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-10 17:45 [RFC PATCH 0/6] x86/entry: cleanups and consistent syscall number handling H. Peter Anvin
2021-05-10 17:45 ` [RFC PATCH 1/6] x86/entry: unify definitions from calling.h and ptrace-abi.h H. Peter Anvin
2021-05-10 17:45 ` [RFC PATCH 2/6] x86/entry: reverse arguments to do_syscall_64() H. Peter Anvin
2021-05-10 17:45 ` [RFC PATCH 3/6] x86/syscall: unconditionally prototype {ia32,x32}_sys_call_table[] H. Peter Anvin
2021-05-10 17:45 ` H. Peter Anvin [this message]
2021-05-10 17:45 ` [RFC PATCH 5/6] x86/entry: use int for syscall number; handle all invalid syscall nrs H. Peter Anvin
2021-05-13 7:39 ` [x86/entry] 55b7c6747c: kernel-selftests.x86.syscall_numbering_64.fail kernel test robot
2021-05-10 17:45 ` [RFC PATCH 6/6] x86/entry: split PUSH_AND_CLEAR_REGS into two submacros H. Peter Anvin
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