chg(ptrace): Add trace with TRACEME.

diff --git a/containers_from_scratch/guide_to_syscalls/myStrace/ptrace-chain.c b/containers_from_scratch/guide_to_syscalls/myStrace/ptrace-chain.c
index e52f0c2..9b2ed72 100644 (file)
--- a/containers_from_scratch/guide_to_syscalls/myStrace/ptrace-chain.c
+++ b/containers_from_scratch/guide_to_syscalls/myStrace/ptrace-chain.c
@@ -15,20 +15,26 @@
 // https://stackoverflow.com/questions/2359581/calling-ptrace-inside-a-ptraced-linux-process
 // https://stackoverflow.com/questions/18437779/do-i-need-to-do-anything-with-a-sigchld-handler-if-i-am-just-using-wait-to-wai
 
+#define TRACEME
+
 extern const char * const sys_siglist[];
 
 static pid_t child_pid = 0;
 
+#ifndef TRACEME
 // Whether SIGSTOP send to tracee right after PTRACE_ATTACH was seen or not.
 static bool attach_stop = false;
+#else
+static bool attach_stop = true;
+#endif
 
 // Is tracee now inside syscall (syscall-enter-stop was seen) or outside
 // (the last syscall-stop was syscall-exit-stop).
 static bool in_syscall = false;
 
 // How to restart ptrace-stopped tracee.
-const enum __ptrace_request ptrace_restart = PTRACE_SYSCALL;
-//const enum __ptrace_request ptrace_restart = PTRACE_CONT;
+//const enum __ptrace_request ptrace_restart = PTRACE_SYSCALL;
+const enum __ptrace_request ptrace_restart = PTRACE_CONT;
 
 // Representation of each process.
 typedef struct worker {
@@ -107,7 +113,7 @@ static void child_has_stopped(pid_t cpid, int status) {
         pref = realloc(pref, n_pref);
         snprintf(pref, n_pref, "[Child %d] (%d)", cpid, csig);
 
-        if (csig == SIGTRAP|0x80) {
+        if (csig == (SIGTRAP|0x80)) {
             printf("%s: Child is traced and and is about to receive '%s' (%d|0x80 = %d)\n", pref, sys_siglist[csig^0x80], csig^0x80, csig);
         } else {
             printf("%s: Child is traced and and is about to receive '%s' (%d)\n", pref, sys_siglist[csig], csig);
@@ -213,9 +219,9 @@ static void child_has_stopped(pid_t cpid, int status) {
                         printf("%s: STOP: stop signal after attach\n", pref);
                         attach_stop = true;
                         printf("%s: STOP: Enabling event tracing\n", pref);
-                        //if(ptrace(PTRACE_SETOPTIONS, child_pid, NULL, PTRACE_O_TRACEEXIT) == -1) {
                         if(ptrace(PTRACE_SETOPTIONS, child_pid, NULL,
                                     PTRACE_O_TRACEEXIT | PTRACE_O_TRACESYSGOOD) == -1) {
+                                    //PTRACE_O_TRACEEXIT) == -1) {
                             perror("ptrace setopts");
                             abort();
                         }
@@ -326,7 +332,8 @@ int main(int  argc, char **argv){
     int i = 0;
     char *myname = workers[i].name;
     void (*mywork) (char*) = workers[i].work;
-    printf("pid%s = %d\n", myname, getpid());
+    pid_t mypid = getpid();
+    printf("pid%s = %d\n", myname, mypid);
 
     for (++i; i < n_workers; i++) {
         char *childname = workers[i].name;
@@ -335,18 +342,28 @@ int main(int  argc, char **argv){
         if (child_pid) {
             printf("pid%s = %d\n", childname, child_pid);
 
-            sleep(1);
-            printf("[%d]: attaching to %s..\n", getpid(), childname);
+            sleep(2);
+#ifndef TRACEME
+            printf("[%d]: attaching to %s..\n", mypid, childname);
             if(ptrace(PTRACE_ATTACH, child_pid, NULL, NULL) == -1){
                 perror("PTRACE_ATTACH");
             }
+#endif
 
             break;
 
         } else {
             myname = workers[i].name;
             mywork = workers[i].work;
-            printf("%s: My pid %d\n", myname, getpid());
+            mypid = getpid();
+            printf("%s: My pid %d\n", myname, mypid);
+#ifdef TRACEME
+            printf("[%d]: requesting trace from parent %d and raising SIGSTOP\n", mypid, getppid());
+            if(ptrace(PTRACE_TRACEME, 0, NULL, NULL) == -1){
+                perror("PTRACE_TRACEME");
+            }
+            raise(SIGSTOP);
+#endif
         }
     }