Openwrt debootstrap chroot fail 'dir-860l mips'

Hi i have build a debian system to usb stick with qemu-debootstrap for mips architecture.
I mount the device with dir 860l system, but i canno't chroot in the system.

I became following answer in shell:
root@OpenWrt:/mnt# chroot sda
chroot: failed to run command ‘/bin/ash’: No such file or directory

Chroot with my home pc work perfect.

cat /proc/cpuinfo:
processor : 3
cpu model : MIPS 1004Kc V2.15
BogoMIPS : 581.63
wait instruction : yes
microsecond timers : yes
tlb_entries : 32
extra interrupt vector : yes
hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
isa : mips1 mips2 mips32r1 mips32r2
ASEs implemented : mips16 dsp mt
Options implemented : tlb 4kex 4k_cache prefetch mcheck ejtag llsc pindexed_dcache userlocal vint perf_cntr_intr_bit cdmm perf
shadow register sets : 1
kscratch registers : 0
package : 0
core : 1
VPE : 1
VCED exceptions : not available
VCEI exceptions : not available

chroot /mnt/sda /bin/bash (you need to supply a valid shell for your chroot).

You might have to recompile OpenWrt with kernel level FPU emulation though, as Debian's mips ISA expects floating point support.