linux-kernel - [PATCH v5 2/4] x86/entry: Simplify _TIF_SYSCALL

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Date:   Tue, 11 Jun 2019 15:56:27 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Will Deacon <will.deacon@....com>,
        Oleg Nesterov <oleg@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Richard Weinberger <richard@....at>, jdike@...toit.com,
        Steve Capper <Steve.Capper@....com>,
        Haibo Xu <haibo.xu@....com>, Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Subject: [PATCH v5 2/4] x86/entry: Simplify _TIF_SYSCALL_EMU handling

The usage of emulated and _TIF_SYSCALL_EMU flags in syscall_trace_enter
is more complicated than required.

Cc: Andy Lutomirski <luto@...nel.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Acked-by: Oleg Nesterov <oleg@...hat.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 arch/x86/entry/common.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

Hi Catalin,

I assume you can now pick up this patch.

Regards,
Sudeep

v4->v5: Updated changelog as suggested by tglx and added his Reviewed-by

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index a986b3c8294c..0a61705d62ec 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -72,23 +72,18 @@ static long syscall_trace_enter(struct pt_regs *regs)

 	struct thread_info *ti = current_thread_info();
 	unsigned long ret = 0;
-	bool emulated = false;
 	u32 work;

 	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
 		BUG_ON(regs != task_pt_regs(current));

-	work = READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;
+	work = READ_ONCE(ti->flags);

-	if (unlikely(work & _TIF_SYSCALL_EMU))
-		emulated = true;
-
-	if ((emulated || (work & _TIF_SYSCALL_TRACE)) &&
-	    tracehook_report_syscall_entry(regs))
-		return -1L;
-
-	if (emulated)
-		return -1L;
+	if (work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
+		ret = tracehook_report_syscall_entry(regs);
+		if (ret || (work & _TIF_SYSCALL_EMU))
+			return -1L;
+	}

 #ifdef CONFIG_SECCOMP
 	/*
--
2.17.1