Simple optimizations in trace()

* strace.c (trace): Calculate WSTOPSIG(status) once,
unify code paths to ptrace(PTRACE_SYSCALL).

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>

diff --git a/strace.c b/strace.c
index 722a0f0b4140c65fcf38e2d85b4431a354fe6220..5ed3da67689884d6259c9ed8daa05f26c6aaea26 100644 (file)
--- a/strace.c
+++ b/strace.c
@@ -2294,7 +2294,7 @@ trace()
 {
        int pid;
        int wait_errno;
-       int status;
+       int status, sig;
        struct tcb *tcp;
 #ifdef LINUX
        struct rusage ru;
@@ -2486,9 +2486,11 @@ trace()
 
                if (status >> 16) {
                        /* Ptrace event (we ignore all of them for now) */
-                       goto tracing;
+                       goto restart_tracee_with_sig_0;
                }
 
+               sig = WSTOPSIG(status);
+
                /*
                 * Interestingly, the process may stop
                 * with STOPSIG equal to some other signal
@@ -2498,7 +2500,7 @@ trace()
                 * so skip the first (lost) execve notification.
                 */
                if ((tcp->flags & TCB_STARTUP) &&
-                   (WSTOPSIG(status) == SIGSTOP || strace_vforked)) {
+                   (sig == SIGSTOP || strace_vforked)) {
                        /*
                         * This flag is there to keep us in sync.
                         * Next time this process stops it should
@@ -2510,7 +2512,8 @@ trace()
                                 * One example is a breakpoint inherited from
                                 * parent through fork().
                                 */
-                               if (clearbpt(tcp) < 0) /* Pretty fatal */ {
+                               if (clearbpt(tcp) < 0) {
+                                       /* Pretty fatal */
                                        droptcb(tcp);
                                        cleanup();
                                        return -1;
@@ -2528,25 +2531,21 @@ trace()
                                }
                        }
 #endif
-                       goto tracing;
+                       goto restart_tracee_with_sig_0;
                }
 
-               if (WSTOPSIG(status) != syscall_trap_sig) {
-                       if (WSTOPSIG(status) == SIGSTOP &&
+               if (sig != syscall_trap_sig) {
+                       if (sig == SIGSTOP &&
                                        (tcp->flags & TCB_SIGTRAPPED)) {
                                /*
                                 * Trapped attempt to block SIGTRAP
                                 * Hope we are back in control now.
                                 */
                                tcp->flags &= ~(TCB_INSYSCALL | TCB_SIGTRAPPED);
-                               if (ptrace_restart(PTRACE_SYSCALL, tcp, 0) < 0) {
-                                       cleanup();
-                                       return -1;
-                               }
-                               continue;
+                               goto restart_tracee_with_sig_0;
                        }
                        if (cflag != CFLAG_ONLY_STATS
-                           && (qual_flags[WSTOPSIG(status)] & QUAL_SIGNAL)) {
+                           && (qual_flags[sig] & QUAL_SIGNAL)) {
                                siginfo_t si;
 #if defined(PT_CR_IPSR) && defined(PT_CR_IIP)
                                long pc = 0;
@@ -2568,20 +2567,16 @@ trace()
                                        tprints("--- ");
                                        printsiginfo(&si, verbose(tcp));
                                        tprintf(" (%s)" PC_FORMAT_STR " ---",
-                                               strsignal(WSTOPSIG(status))
+                                               strsignal(sig)
                                                PC_FORMAT_ARG);
                                } else
                                        tprintf("--- %s by %s" PC_FORMAT_STR " ---",
-                                               strsignal(WSTOPSIG(status)),
-                                               signame(WSTOPSIG(status))
+                                               strsignal(sig),
+                                               signame(sig)
                                                PC_FORMAT_ARG);
                                printtrailer();
                        }
-                       if (ptrace_restart(PTRACE_SYSCALL, tcp, WSTOPSIG(status)) < 0) {
-                               cleanup();
-                               return -1;
-                       }
-                       continue;
+                       goto restart_tracee;
                }
 
                /* We handled quick cases, we are permitted to interrupt now. */
@@ -2617,10 +2612,12 @@ trace()
                        }
                        continue;
                }
-       tracing:
+ restart_tracee_with_sig_0:
+               sig = 0;
+ restart_tracee:
                /* Remember current print column before continuing. */
                tcp->curcol = curcol;
-               if (ptrace_restart(PTRACE_SYSCALL, tcp, 0) < 0) {
+               if (ptrace_restart(PTRACE_SYSCALL, tcp, sig) < 0) {
                        cleanup();
                        return -1;
                }