GCC 9 stack protector comparing address of stack guard not value

Hi,

I have been testing GCC stack protector on bare metal Cortex-M4 using gcc-arm-none-eabi-9-2020-q2-update and have observed a difference in emitted instructions versus the last GCC 8.x release.

Compiled SSP test code with: -std=gnu11 -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi-hard -ffunction-sections -fdata-sections -fstack-protector-strong --specs=nano.spes --specs=nosys.specs

Map file:

 .bss.__stack_chk_guard
                0x000000000011ad1c        0x4 /home/void/cc/gcc-arm-none-eabi-9-2020-q2-update/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard/libg_nano.a(lib_a-stack_protector.o)
                0x000000000011ad1c                __stack_chk_guard

object dump (-xDS)

000d9144 <ssp_test1>:
   d9144:    b500          push    {lr}
   d9146:    4b0e          ldr    r3, [pc, #56]    ; (d9180 <ssp_test1+0x3c>)   NOTE: R3 = 0x000da9b4  literal pool address
   d9148:    490e          ldr    r1, [pc, #56]    ; (d9184 <ssp_test1+0x40>)
   d914a:    b093          sub    sp, #76    ; 0x4c
   d914c:    681b          ldr    r3, [r3, #0]                                                       NOTE: R3 = 0x0011ad1c address of __stack_chk_guard
   d914e:    9311          str    r3, [sp, #68]    ; 0x44                                       NOTE: Saves address of __stack_chk_guard, never loads the value!
   d9150:    f04f 0300     mov.w    r3, #0                                                      NOTE: clear address of __stack_chk_guard. Is this part of GCC PR85434?
   d9154:    aa01          add    r2, sp, #4
   d9156:    f44f 138c     mov.w    r3, #1146880    ; 0x118000
   d915a:    4618          mov    r0, r3
   d915c:    3304          adds    r3, #4
   d915e:    6800          ldr    r0, [r0, #0]
   d9160:    f842 0b04     str.w    r0, [r2], #4
   d9164:    428b          cmp    r3, r1
   d9166:    d1f8          bne.n    d915a <ssp_test1+0x16>
   d9168:    4b05          ldr    r3, [pc, #20]    ; (d9180 <ssp_test1+0x3c>) NOTE: R3 = 0x000da9b4
   d916a:    9809          ldr    r0, [sp, #36]    ; 0x24                                   
   d916c:    681a          ldr    r2, [r3, #0]                                                    NOTE: R2 = 0x0011ad1c address of __stack_chk_guard
   d916e:    9b11          ldr    r3, [sp, #68]    ; 0x44                                    NOTE: R3 = address of __stack_chk_guard save in function prolog
   d9170:    405a          eors    r2, r3                                                         NOTE: Address match not guard value!
   d9172:    d001          beq.n    d9178 <ssp_test1+0x34>
   d9174:    f001 fbc0     bl    da8f8 <__stack_chk_fail>
   d9178:    b013          add    sp, #76    ; 0x4c
   d917a:    f85d fb04     ldr.w    pc, [sp], #4
   d917e:    bf00          nop
   d9180:    000da9b4             ; <UNDEFINED> instruction: 0x000da9b4
   d9184:    00118040     andseq    r8, r1, r0, asr #32

000da9b0 <_global_impure_ptr>:
   da9b0:    00118208     andseq    r8, r1, r8, lsl #4
   da9b4:    0011ad1c     andseq    sl, r1, ip, lsl sp
   da9b8:    6c707041     ldclvs    0, cr7, [r0], #-260    ; 0xfffffefc