Why did I get the same result after using rand()?

Which seed value are you using?
If you usea constant value for seed, you will always receive the same row of rand() values.

Usually you should use something like

#include <time.h>

  srand (time(NULL));

to initialize the random generator with a value that is different in every execution.

I am using different seeds.

I get the same value every rand()

0011a774 <srand>:
  11a774: 4b02 ldr r3, [pc, #8] ; (11a780 <srand+0xc>)
  11a776: 2100 movs r1, #0
  11a778: 681b ldr r3, [r3, #0]
  11a77a: e9c3 012a strd r0, r1, [r3, #168] ; 0xa8
  11a77e: 4770 bx lr
  11a780: 00200430 .word 0x00200430

0011a784 <rand>:
  11a784: b430 push {r4, r5}
  11a786: 4b0c ldr r3, [pc, #48] ; (11a7b8 <rand+0x34>)
  11a788: 4d0c ldr r5, [pc, #48] ; (11a7bc <rand+0x38>)
  11a78a: 681c ldr r4, [r3, #0]
  11a78c: 490c ldr r1, [pc, #48] ; (11a7c0 <rand+0x3c>)
  11a78e: f8d4 20a8 ldr.w r2, [r4, #168] ; 0xa8
  11a792: f8d4 00ac ldr.w r0, [r4, #172] ; 0xac
  11a796: fb05 f502 mul.w r5, r5, r2
  11a79a: fba2 2301 umull r2, r3, r2, r1
  11a79e: fb01 5100 mla r1, r1, r0, r5
  11a7a2: 3201 adds r2, #1
  11a7a4: 440b add r3, r1
  11a7a6: f143 0300 adc.w r3, r3, #0
  11a7aa: e9c4 232a strd r2, r3, [r4, #168] ; 0xa8
  11a7ae: f023 4000 bic.w r0, r3, #2147483648 ; 0x80000000
  11a7b2: bc30 pop {r4, r5}
  11a7b4: 4770 bx lr
  11a7b6: bf00 nop
  11a7b8: 00200430 .word 0x00200430
  11a7bc: 5851f42d .word 0x5851f42d
  11a7c0: 4c957f2d .word 0x4c957f2d

What is the part of the source code where us call rand and srand?

oops, typo with wrong autocorrect ... where you call ...

I run the program on cm3, did I link the wrong libc.a? which one libc.a should I link?

srand(HW_TIME); the seed was got from HW register.
printf("%d,%d,%d", rand(), rand(), rand()); the three value were the same.

I linked
4.8 2014q3\lib\gcc\arm-none-eabi\4.8.4\armv7-m for libgcc.a
4.8 2014q3\arm-none-eabi\lib\armv7-m for libc.a