linux-kernel - [PATCH v4 2/4] x86: simplify _TIF_SYSCALL

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Message-Id: <20190523090618.13410-3-sudeep.holla@arm.com>
Date:   Thu, 23 May 2019 10:06:16 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Oleg Nesterov <oleg@...hat.com>,
        Richard Weinberger <richard@....at>, jdike@...toit.com,
        Steve Capper <Steve.Capper@....com>,
        Haibo Xu <haibo.xu@....com>, Bin Lu <bin.lu@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Subject: [PATCH v4 2/4] x86: simplify _TIF_SYSCALL_EMU handling

The usage of emulated/_TIF_SYSCALL_EMU flags in syscall_trace_enter
seems to be bit overcomplicated than required. Let's simplify it.

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

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