From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Sat, 16 Feb 2013 13:25:56 +0000 (+0100)
Subject: Simple optimization in get_error
X-Git-Tag: v4.8~152
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c956ef085f5685b47bd7a66d0bff5abcb0a50484;p=strace

Simple optimization in get_error

* defs.h: Define SCNO_IN_RANGE(scno) macro.
* syscall.c (get_error): Change return type to void.
Use SCNO_IN_RANGE instead of SCNO_IS_VALID.
(trace_syscall_exiting): Stop checking get_error() return value.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
---

diff --git a/defs.h b/defs.h
index f641e0da..3d5f3000 100644
--- a/defs.h
+++ b/defs.h
@@ -753,5 +753,12 @@ extern unsigned nioctlents;
 extern const char *const *signalent;
 extern unsigned nsignals;
 
+/*
+ * If you need non-NULL sysent[scno].sys_func and sysent[scno].sys_name
+ */
 #define SCNO_IS_VALID(scno) \
-  ((unsigned long)(scno) < nsyscalls && sysent[scno].sys_func)
+	((unsigned long)(scno) < nsyscalls && sysent[scno].sys_func)
+
+/* Only ensures that sysent[scno] isn't out of range */
+#define SCNO_IN_RANGE(scno) \
+	((unsigned long)(scno) < nsyscalls)
diff --git a/syscall.c b/syscall.c
index 6078cb7a..5c0d5808 100644
--- a/syscall.c
+++ b/syscall.c
@@ -2073,12 +2073,12 @@ is_negated_errno_x32(unsigned long long val)
  * -1: error, trace_syscall_exiting() should print error indicator
  *    ("????" etc) and bail out.
  */
-static int
+static void
 get_error(struct tcb *tcp)
 {
 	int u_error = 0;
 	int check_errno = 1;
-	if (SCNO_IS_VALID(tcp->scno)
+	if (SCNO_IN_RANGE(tcp->scno)
 	 && (sysent[tcp->scno].sys_flags & SYSCALL_NEVER_FAILS)
 	) {
 		check_errno = 0;
@@ -2304,7 +2304,6 @@ get_error(struct tcb *tcp)
 	}
 #endif
 	tcp->u_error = u_error;
-	return 1;
 }
 
 static void
@@ -2358,14 +2357,11 @@ trace_syscall_exiting(struct tcb *tcp)
 	res = (get_regs_error ? -1 : get_syscall_result(tcp));
 	if (res == 1) {
 		syscall_fixup_on_sysexit(tcp); /* never fails */
-		res = get_error(tcp); /* returns 1 or -1 */
-		if (res == 1) {
-			if (need_fork_exec_workarounds)
-				syscall_fixup_for_fork_exec(tcp);
-			if (filtered(tcp)) {
-				goto ret;
-			}
-		}
+		get_error(tcp); /* never fails */
+		if (need_fork_exec_workarounds)
+			syscall_fixup_for_fork_exec(tcp);
+		if (filtered(tcp))
+			goto ret;
 	}
 
 	if (cflag) {