$ adb -d shell
$ mount
mount
rootfs / rootfs ro,relatime 0 0
tmpfs /dev tmpfs rw,relatime,mode=111 0 0
devpts /dev/pts devpts rw,relatime,mode=600 0 0
proc /proc proc rw,relatime 0 0
sysfs /sys sysfs rw,relatime 0 0
none /acct cgroup rw,relatime,cpuacct 0 0
tmpfs /mnt/asec tmpfs rw,relatime,mode=755,gid=1000 0 0
tmpfs /mnt/obb tmpfs rw,relatime,mode=755,gid=1000 0 0
tmpfs /mnt/usb tmpfs rw,relatime,mode=755,gid=1000 0 0
tmpfs /app-cache tmpfs rw,relatime,size=7168k 0 0
none /dev/cpuctl cgroup rw,relatime,cpu 0 0
/dev/block/mmcblk0p9 /system ext4 ro,relatime,barrier=1,data=ordered 0 0
/dev/block/mmcblk0p7 /cache ext4 rw,nosuid,nodev,noatime,barrier=1,data=ordered
/dev/block/mmcblk0p1 /efs ext4 rw,nosuid,nodev,noatime,barrier=1,data=ordered 0
nil /sys/kernel/debug debugfs rw,relatime 0 0
/dev/block/mmcblk0p10 /data ext4 rw,nosuid,nodev,noatime,barrier=1,data=ordered,
/dev/block/mmcblk0p4 /mnt/.lfs j4fs rw,relatime 0 0
/dev/block/vold/179:11 /mnt/sdcard vfat rw,dirsync,nosuid,nodev,noexec,noatime,n
epage=cp437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro,discard 0
I followed this link and tried to mount the filesystem as follows but I got a permission error.
$ mount -o rw,remount -t yaffs2 /dev/block/mmcblk0p9 /system
mount: Operation not permitted
adb push foo.txt /sdcard/foo.txt