pxeboot: make the tftp loader use the option root-path directive

pxeboot in tftp loader mode (when built with LOADER_TFTP_SUPPORT) now
prefix all the path to open with the path obtained via the option 'root-path'
directive.

This allows to be able to use the traditional content /boot out of box. Meaning
it now works pretty much like all other loaders. It simplifies hosting hosting
multiple version of FreeBSD on a tftp server.

As a consequence, pxeboot does not look anymore for a pxeboot.4th (which was
never provided)

Note: that pxeboot in tftp loader mode is not built by default.

Reviewed by:	rpokala
Relnotes:	yes
Sponsored by:	Gandi.net
Differential Revision:	https://reviews.freebsd.org/D4590

UPDATING

@@ -31,6 +31,12 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 11.x IS SLOW:
 	disable the most expensive debugging functionality run
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20151216:
+	The tftp loader (pxeboot) now uses the option root-path directive. As a
+	consequence it no longer looks for a pxeboot.4th file on the tftp
+	server. Instead it uses the regular /boot infrastructure as with the
+	other loaders.
+
 20151211:
 	The code to start recording plug and play data into the modules has
 	been committed. While the old tools will properly build a new kernel,

lib/libstand/tftp.c

@@ -399,6 +399,8 @@ tftp_open(const char *path, struct open_file *f)
 	struct tftp_handle *tftpfile;
 	struct iodesc  *io;
 	int             res;
+	size_t          pathsize;
+	const char     *extraslash;
 
 	if (strcmp(f->f_dev->dv_name, "net") != 0) {
 #ifdef __i386__
@@ -424,10 +426,22 @@ tftp_open(const char *path, struct open_file *f)
 
 	io->destip = servip;
 	tftpfile->off = 0;
-	tftpfile->path = strdup(path);
+	pathsize = (strlen(rootpath) + 1 + strlen(path) + 1) * sizeof(char);
+	tftpfile->path = malloc(pathsize);
 	if (tftpfile->path == NULL) {
-	    free(tftpfile);
-	    return(ENOMEM);
+		free(tftpfile);
+		return(ENOMEM);
+	}
+	if (rootpath[strlen(rootpath) - 1] == '/' || path[0] == '/')
+		extraslash = "";
+	else
+		extraslash = "/";
+	res = snprintf(tftpfile->path, pathsize, "%s%s%s",
+	    rootpath, extraslash, path);
+	if (res < 0 || res > pathsize) {
+		free(tftpfile->path);
+		free(tftpfile);
+		return(ENOMEM);
 	}
 
 	res = tftp_makereq(tftpfile);

sys/boot/i386/libi386/libi386.h

@@ -123,5 +123,4 @@ int	bi_load32(char *args, int *howtop, int *bootdevp, vm_offset_t *bip,
 int	bi_load64(char *args, vm_offset_t addr, vm_offset_t *modulep,
 	    vm_offset_t *kernend, int add_smap);
 
-char	*pxe_default_rc(void);
 void	pxe_enable(void *pxeinfo);

sys/boot/i386/libi386/pxe.c

@@ -288,8 +288,10 @@ pxe_open(struct open_file *f, ...)
 		bootp(pxe_sock, BOOTP_PXE);
 		if (rootip.s_addr == 0)
 			rootip.s_addr = bootplayer.sip;
+#ifdef LOADER_NFS_SUPPORT
 		if (!rootpath[0])
 			strcpy(rootpath, PXENFSROOTPATH);
+#endif
 
 		for (i = 0; rootpath[i] != '\0' && i < FNAME_SIZE; i++)
 			if (rootpath[i] == ':')
@@ -317,6 +319,7 @@ pxe_open(struct open_file *f, ...)
 		setenv("boot.nfsroot.path", rootpath, 1);
 #else
 		setenv("boot.netif.server", inet_ntoa(rootip), 1);
+		setenv("boot.tftproot.path", rootpath, 1);
 #endif
 		setenv("dhcp.host-name", hostname, 1);
 
@@ -705,26 +708,3 @@ readudp(struct iodesc *h, void *pkt, size_t len, time_t timeout)
 	uh->uh_sport = udpread_p->s_port;
 	return udpread_p->buffer_size;
 }
-
-char *
-pxe_default_rc(void)
-{
-	char *rc;
-	size_t count, rcsz;
-
-	/* XXX It may not be a good idea to modify the PXE boot file. */
-	rc = (char *)bootplayer.bootfile;
-	rcsz = sizeof(bootplayer.bootfile);
-
-	/* Ignore how we define rc and rcsz above -- it can change. */
-	if (rcsz < 6)
-		return (NULL);
-	if (*rc == '\0') {
-		strncpy(rc, "pxeboot", rcsz);
-		rc[rcsz - 1] = '\0';
-	}
-	count = strlen(rc);
-	strncat(rc, ".4th", rcsz - count - 1);
-	printf("PXE: loading Forth from %s\n", rc);
-	return (rc);
-}

sys/boot/i386/loader/main.c

@@ -196,11 +196,6 @@ main(void)
     
     bios_getsmap();
 
-#ifdef LOADER_TFTP_SUPPORT
-    if (kargs->bootflags & KARGS_FLAGS_PXE)
-	interact(pxe_default_rc());
-    else
-#endif
     interact(NULL);
 
     /* if we ever get here, it is an error */