Re: [patch 3/4] entry: Make return type of syscall_trace_enter() bool

From: Thomas Gleixner <tglx@kernel.org>

This prepares for changing the return types of
syscall_enter_from_user_mode[_work]() to bool, which in turn separates the
decision of invoking the syscall from the syscall number, which might have
been changed in the call by ptrace, seccomp, tracing.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
---
 include/linux/entry-common.h |   18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h

@@ -72,7 +72,7 @@ static __always_inline long syscall_trac
 	 */
 	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
 		if (syscall_user_dispatch(regs))
-			return -1L;
+			return false;
 	}
 
 	/*

@@ -87,13 +87,13 @@ static __always_inline long syscall_trac
 	if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
 		if (!arch_ptrace_report_syscall_permit_entry(regs) ||
 		    (work & SYSCALL_WORK_SYSCALL_EMU))
-			return -1L;
+			return false;
 	}
 
 	/* Do seccomp after ptrace, to catch any tracer changes. */
 	if (work & SYSCALL_WORK_SECCOMP) {
 		if (!__seccomp_permit_syscall())
-			return -1L;
+			return false;
 	}
 
 	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))

@@ -102,8 +102,7 @@ static __always_inline long syscall_trac
 	if (unlikely(audit_context()))
 		syscall_enter_audit(regs);
 
-	/* Either of the above might have changed the syscall number */
-	return syscall_get_nr(current, regs);
+	return true;
 }
 
 /**

@@ -133,8 +132,13 @@ static __always_inline long syscall_ente
 {
 	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
 
-	if (work & SYSCALL_WORK_ENTER)
-		syscall = syscall_trace_enter(regs, work, syscall);
+	if (work & SYSCALL_WORK_ENTER) {
+		if (!syscall_trace_enter(regs, work, syscall))
+			return -1L;
+
+		/* Reread the syscall number as it might have been modified */
+		syscall = syscall_get_nr(current, regs);
+	}