Changeset 3322Tweet

Timestamp:

Nov 10, 2008, 11:51:29 PM (14 years ago)

Author:

Pascal Terjan

Message:

• Add comments to mytrace_exec

File:

• neercs/trunk/src/mytrace.c (modified) (3 diffs)

neercs/trunk/src/mytrace.c

@@ -335 +335 @@
     ssize_t envsize = 16*1024;
     int ret, fd, l, l2;
-    char *newargv[] = { NULL };
+    char *nullp = NULL;
     ssize_t r;
 
@@ -373 +373 @@
     }
     envsize = r;
+    l2 = sizeof(char *); /* Size of a pointer */
+    p2 = regs.RSP;
+
+    /* First argument is the command string */
     l = strlen(command)+1;
-    l2 = sizeof(char *);
-    p2 = regs.RSP;
     memcpy_into_target(t, p2, command, l);
     p2 += l;
+
+    /* Second argument is argv */
     argvaddr = p2;
+    /* argv[0] is a pointer to the command string */
     memcpy_into_target(t, p2, (char *)&regs.RSP, l2);
     p2 += l2;
-    memcpy_into_target(t, p2, (char *)&newargv, l2);
+    /* Then follows a NULL pointer */
+    memcpy_into_target(t, p2, (char *)&nullp, l2);
     p2 += l2;
+
+    /* Third argument is the environment */
+    /* First, copy all the strings */
     memcpy_into_target(t, p2, env, envsize);
     envaddr = p2;
     p2 += envsize;
+    /* Then write an array of pointers to the strings */
     envptraddr = p2;
     p = env;
@@ -395 +405 @@
         p += strlen(p)+1;
     }
-    memcpy_into_target(t, p2, (char *)&newargv, l2);
+    /* And have a NULL pointer at the end of the array */
+    memcpy_into_target(t, p2, (char *)&nullp, l2);
     free(env);
+
     ret = remote_syscall(t, MYCALL_EXECVE, regs.RSP, argvaddr, envptraddr);