[PATCH 3/6] x86: clean up _TIF_SYSCALL_EMU handling using ptrace_syscall_enter hook

Sudeep Holla
2019-02-28T18:33:12Z

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@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.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