dtrace anonymous tracing

[Prashanth Kumar]

Looks like code for anonymous tracing is already present. If you read the /boot/dtrace.dof
file from the loader and set it as a environment variable it will work.
I tested it with the following patch just to see whether it would work.

------------------------------------------------------------------------------------------------------------------------
--- main.c	2013-11-21 12:03:57.000000000 +0400
+++ /usr/src/sys/boot/i386/loader/main.c	2013-11-21 12:44:23.000000000 +0400
@@ -84,6 +84,11 @@
 main(void)
 {
     int			i;
+    
+    char *dtracedof = "/boot/dtrace.dof";
+    int fd, n=0, l=0;
+    char *buf, *s, *e, c[32];
+    struct stat dstat;
 
     /* Pick up arguments */
     kargs = (void *)__args;
@@ -190,6 +195,40 @@
     extract_currdev();				/* set $currdev and $loaddev */
     setenv("LINES", "24", 1);			/* optional */
     
+    if ((fd = open(dtracedof, O_RDONLY)) == -1) 
+		printf("Error opening dtrace file %s\n", dtracedof);
+    else if (fstat(fd, &dstat) == -1) 
+		printf("Can't access  %s\n", dtracedof);
+    else if ((buf = malloc(dstat.st_size+1)) == NULL)
+    		printf("Error allocating mem size %d - %s\n", dstat.st_size, dtracedof);
+    else if (read(fd, buf, dstat.st_size) < dstat.st_size)
+		printf("Error reading file %s size %d\n", dtracedof, dstat.st_size);
+    else {
+    	for (i = 0; ; i++) {
+	    (void) sprintf(c, "dof-data-%d", i);
+	    l = strlen(c);
+	    if (strncmp(c, buf, l) != 0) {
+		printf("Malformed name %s\n", c);
+		close(fd);
+		free(buf);
+		break;
+	    }
+    	    s = e = &buf[l+1];
+	    n += l+1;
+	    while(*e != '\n')
+		e++;
+	    *e = 0;
+	    //printf("string %s %s\n",c,  s);
+	    setenv(c, s, 1);
+	    n += e - s;
+	    n++;
+	    if (n < dstat.st_size) 
+		buf = ++e;
+	    else
+		break;
+	}
+    }	
+    
     bios_getsmap();
 
     interact();			/* doesn't return */
-----------------------------------------------------------------------------------------------------------------------------

Kernel environment variable value has to be in increased.
In sys/kenv.h, 
--------------------------------------------------------------------------
--- kenv.h	2013-11-21 14:31:50.000000000 +0400
+++ /usr/src/sys/sys/kenv.h	2013-11-21 14:32:05.000000000 +0400
@@ -38,6 +38,6 @@
 #define KENV_DUMP	3
 
 #define KENV_MNAMELEN	128	/* Maximum name length (for the syscall) */
-#define KENV_MVALLEN	128	/* Maximum value length (for the syscall) */
+#define KENV_MVALLEN	3000	/* Maximum value length (for the syscall) */
 
 #endif /* !_SYS_KENV_H_ */
----------------------------------------------------------------------------------------------------------------
example : $> dtrace -A vboxguest
                $> reboot

              $>dtrace -a

Probably be better to read dtrace.dof from dtrace module itself.

regards
Prashanth

--------------------------------------------
On Wed, 20/11/13, Andriy Gapon <avg at FreeBSD.org> wrote:

 Subject: Re: dtrace anonymous tracing
 To: "Prashanth Kumar" <pra_udupi at yahoo.co.in>, freebsd-dtrace at FreeBSD.org
 Date: Wednesday, 20 November, 2013, 4:45 PM
 
 on 20/11/2013 12:18 Prashanth Kumar
 said the following:
 > Is it possible to enable dtrace anonymous tracing in
 freebsd?
 > 
 
 Not without some kernel coding, I believe :-)
 
 -- 
 Andriy Gapon