Agptek Rocker: Restrict root directory to SD only

Actual / of underlying linux OS should not be available to user.
I am still not sure if implementation is correct. It doesn't
perform any relative path sandboxing for example.

Change-Id: Ic577a10f3947f6e950e2c4d03173f9f207395eb7

firmware/export/rbpaths.h

@@ -51,8 +51,6 @@
 #elif defined(DX50) || defined(DX90)
 /* Where to put save files like recordings, playlists, screen dumps ...*/
 #define HOME_DIR "/mnt/sdcard"
-#elif defined(AGPTEK_ROCKER)
-#define HOME_DIR "/mnt/sd_0"
 #else
 #define HOME_DIR "/"
 #endif

firmware/target/hosted/filesystem-app.c

@@ -37,6 +37,10 @@
 #include "logf.h"
 
 
+#if defined(AGPTEK_ROCKER) && !defined(BOOTLOADER)
+#define PIVOT_ROOT "/mnt/sd_0"
+#endif
+
 #if (CONFIG_PLATFORM & PLATFORM_ANDROID)
 static const char rbhome[] = "/sdcard";
 #elif (CONFIG_PLATFORM & (PLATFORM_SDL|PLATFORM_MAEMO|PLATFORM_PANDORA)) \
@@ -205,6 +209,10 @@ const char * handle_special_dirs(const char *dir, unsigned flags,
 #endif
 #ifdef HAVE_MULTIDRIVE
     dir = handle_special_links(dir, flags, buf, bufsize);
+#endif
+#ifdef PIVOT_ROOT
+    snprintf(buf, bufsize, "%s/%s", PIVOT_ROOT, dir);
+    dir = buf;
 #endif
     return dir;
 }

firmware/target/hosted/lc-unix.c

@@ -21,6 +21,7 @@
 
 #include <string.h> /* size_t */
 #include <dlfcn.h>
+#include "file.h"
 #include "debug.h"
 #include "load_code.h"
 
@@ -28,7 +29,11 @@ void *lc_open(const char *filename, unsigned char *buf, size_t buf_size)
 {
     (void)buf;
     (void)buf_size;
-    void *handle = dlopen(filename, RTLD_NOW);
+    char path[MAX_PATH];
+
+    const char *fpath = handle_special_dirs(filename, 0, path, sizeof(path));
+
+    void *handle = dlopen(fpath, RTLD_NOW);
     if (handle == NULL)
     {
         DEBUGF("failed to load %s\n", filename);

tools/configure

@@ -4212,7 +4212,6 @@ fi
     t_cpu="hosted"
     t_manufacturer="agptek"
     t_model="rocker"
-    rbdir='/mnt/sd_0/.rockbox'
     mipsellinuxcc
     ;;