linux-kernel - [PATCH 3/6] x86: clean up _TIF_SYSCALL_EMU handling using ptrace_syscall

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Message-Id: <20190228183220.15626-4-sudeep.holla@arm.com>
Date:   Thu, 28 Feb 2019 18:32:17 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Oleg Nesterov <oleg@...hat.com>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...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>,
        Borislav Petkov <bp@...en8.de>
Subject: [PATCH 3/6] x86: clean up _TIF_SYSCALL_EMU handling using ptrace_syscall_enter hook

Now that we have a new hook ptrace_syscall_enter that can be called from
syscall entry code and it handles PTRACE_SYSEMU in generic code, we
can do some cleanup using the same in syscall_trace_enter.

Further the extra logic to find single stepping PTRACE_SYSEMU_SINGLESTEP
in syscall_slow_exit_work seems unnecessary. Let's remove the same.

Cc: Andy Lutomirski <luto@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 arch/x86/entry/common.c | 22 ++++------------------
 1 file changed, 4 insertions(+), 18 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 7bc105f47d21..36457c1f87d2 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -70,22 +70,16 @@ 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;
-
-	if (unlikely(work & _TIF_SYSCALL_EMU))
-		emulated = true;
-
-	if ((emulated || (work & _TIF_SYSCALL_TRACE)) &&
-	    tracehook_report_syscall_entry(regs))
+	if (unlikely(ptrace_syscall_enter(regs)))
 		return -1L;
 
-	if (emulated)
+	work = READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;
+	if ((work & _TIF_SYSCALL_TRACE) && tracehook_report_syscall_entry(regs))
 		return -1L;
 
 #ifdef CONFIG_SECCOMP
@@ -227,15 +221,7 @@ static void syscall_slow_exit_work(struct pt_regs *regs, u32 cached_flags)
 	if (cached_flags & _TIF_SYSCALL_TRACEPOINT)
 		trace_sys_exit(regs, regs->ax);
 
-	/*
-	 * If TIF_SYSCALL_EMU is set, we only get here because of
-	 * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
-	 * We already reported this syscall instruction in
-	 * syscall_trace_enter().
-	 */
-	step = unlikely(
-		(cached_flags & (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU))
-		== _TIF_SINGLESTEP);
+	step = unlikely((cached_flags & _TIF_SINGLESTEP));
 	if (step || cached_flags & _TIF_SYSCALL_TRACE)
 		tracehook_report_syscall_exit(regs, step);
 }
-- 
2.17.1