BZ467652: support old-style stap -c "FOO > BAR" usage by backing down to sh -c if needed.

2 files changed, 32 insertions, 9 deletions

diff --git a/NEWS b/NEWS
index 2471c3af..b849011a 100644
--- a/NEWS
+++ b/NEWS
@@ -29,8 +29,11 @@
 
 - Target process mode (stap -c CMD or -x PID) now implicitly restricts all
   "process.*" probes to the given child process.  (It does not affect
-  kernel.* or other probe types.)  The CMD string is now executed directly,
-  rather than via a /bin/sh -c subshell.
+  kernel.* or other probe types.)  The CMD string is normally run directly,
+  rather than via a /bin/sh -c subshell, since then utrace/uprobe probes
+  receive a fairly "clean" event stream.  If metacharacters like
+  redirection operators were present in CMD, then "sh -c CMD" is still
+  used, and utrace/uprobe probes will receive events from the shell.
 
      % stap -e 'probe process.syscall, process.end {
                    printf("%s %d %s\n", execname(), pid(), pp())}'\
diff --git a/runtime/staprun/mainloop.c b/runtime/staprun/mainloop.c
index 8db42d7d..9221d8a6 100644
--- a/runtime/staprun/mainloop.c
+++ b/runtime/staprun/mainloop.c
@@ -118,6 +118,7 @@ void start_cmd(void)
     /* We're in the target process.	 Let's start the execve of target_cmd, */
     int rc;
     wordexp_t words;
+    char *sh_c_argv[4] = { NULL, NULL, NULL, NULL };
 
     a.sa_handler = SIG_DFL;
     sigaction(SIGINT, &a, NULL);
@@ -127,14 +128,32 @@ void start_cmd(void)
        probe a new child process, not a mishmash of shell-interpreted
        stuff. */
     rc = wordexp (target_cmd, & words, WRDE_NOCMD|WRDE_UNDEF);
-    switch (rc) 
+    if (rc == WRDE_BADCHAR)
       {
-      case 0: break;
-      case WRDE_BADCHAR: _err ("wordexp: invalid shell meta-character in -c COMMAND\n"); _exit(1);
-      case WRDE_SYNTAX: _err ("wordexp: syntax error (unmatched quotes?) in -c COMMAND\n"); _exit(1);
-      default: _err ("wordexp: parsing error (%d)\n", rc); _exit (1);
+        /* The user must have used a shell metacharacter, thinking that
+           we use system(3) to evaluate 'stap -c CMD'.  We could generate
+           an error message ... but let's just do what the user meant.  
+           rhbz 467652. */
+        sh_c_argv[0] = "sh";
+        sh_c_argv[1] = "-c";
+        sh_c_argv[2] = target_cmd;
+        sh_c_argv[3] = NULL;
+      }
+    else
+      {
+        switch (rc) 
+          {
+          case 0: 
+            break;
+          case WRDE_SYNTAX:
+            _err ("wordexp: syntax error (unmatched quotes?) in -c COMMAND\n");
+            _exit(1);
+          default:
+            _err ("wordexp: parsing error (%d)\n", rc); 
+            _exit (1);
+          }
+        if (words.we_wordc < 1) { _err ("empty -c COMMAND"); _exit (1); }
       }
-    if (words.we_wordc < 1) { _err ("empty -c COMMAND"); _exit (1); }
 
     rc = ptrace (PTRACE_TRACEME, 0, 0, 0);
     if (rc < 0) perror ("ptrace me");
@@ -149,7 +168,8 @@ void start_cmd(void)
     /* Note that execvp() is not a direct system call; it does a $PATH
        search in glibc.  We would like to filter out these dummy syscalls
        from the utrace events seen by scripts. */
-    if (execvp (words.we_wordv[0], words.we_wordv) < 0)
+    if (execvp ((sh_c_argv[0] == NULL ? words.we_wordv[0] : sh_c_argv[0]),
+                (sh_c_argv[0] == NULL ? words.we_wordv    : sh_c_argv)) < 0)
       perror(target_cmd);
 
       /* (There is no need to wordfree() words; they are or will be gone.) */