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ARM9 STR912FW44 word32 misalignment in external RAM

Øyvind Teig

I have a struct containing several word8, word16 and word32. Writing a full 32-bits value causes mis-writing to the previous 32-bits value. 2 bytes go to the correct place, and 2 bytes to the previous. Having 8 or 16 bits entities in the same struct works fine and they align correctly. I don't use __packed. Some times I don't see the overwritten data, when I assume it's written to padded cells. We have 16 bits external ram for this. Little endian. Keil tool, ARM compiler.

Øyvind Teig
home.no.net/.../work.html

Parents
  • 0 in reply to Mik Kleshov

    It's pointers as well as other word32 entities:

    typedef struct
{
    ...
    ...
    word8_a                     Byte_1;
    word8_a                     Byte_2;
    word16_a                    Word_1;
    word8_a                     Byte_3;
    size_t                      Fence_1;
    size_t                      Fence_2;
    size_t*                     Address_1;
    size_t*                     Address_2;
    word16_a                    Word_2;
    word8_a                     Byte_4;
    word8_a                     Byte_5;
    ApplCtx_a*                  ApplCtxPtr; // Application context
    //
} Context_a;

{
    ContextPtr->Byte_1     = 1;
    ContextPtr->Byte_2     = 2;
    ContextPtr->Byte_3     = 3;
    ContextPtr->Byte_4     = 4;
    ContextPtr->Word_1     = 0xAA22;
    ContextPtr->Word_2     = 0xBB33;
    ContextPtr->Fence_1    = 0x12345678;
    ContextPtr->Fence_2    = 0x55AA6677;
    ContextPtr->Address_1  = &(ContextPtr->Fence_1);
    ContextPtr->Address_2  = &(ContextPtr->Fence_2);
    ExternalApplCtxPtr     = (ApplCtx_a*) MEM_ALLOC_F(sizeof(ApplCtx_a));
    ContextPtr->ApplCtxPtr = ExternalApplCtxPtr;
}

Reply
  • 0 in reply to Mik Kleshov

    It's pointers as well as other word32 entities:

    typedef struct
{
    ...
    ...
    word8_a                     Byte_1;
    word8_a                     Byte_2;
    word16_a                    Word_1;
    word8_a                     Byte_3;
    size_t                      Fence_1;
    size_t                      Fence_2;
    size_t*                     Address_1;
    size_t*                     Address_2;
    word16_a                    Word_2;
    word8_a                     Byte_4;
    word8_a                     Byte_5;
    ApplCtx_a*                  ApplCtxPtr; // Application context
    //
} Context_a;

{
    ContextPtr->Byte_1     = 1;
    ContextPtr->Byte_2     = 2;
    ContextPtr->Byte_3     = 3;
    ContextPtr->Byte_4     = 4;
    ContextPtr->Word_1     = 0xAA22;
    ContextPtr->Word_2     = 0xBB33;
    ContextPtr->Fence_1    = 0x12345678;
    ContextPtr->Fence_2    = 0x55AA6677;
    ContextPtr->Address_1  = &(ContextPtr->Fence_1);
    ContextPtr->Address_2  = &(ContextPtr->Fence_2);
    ExternalApplCtxPtr     = (ApplCtx_a*) MEM_ALLOC_F(sizeof(ApplCtx_a));
    ContextPtr->ApplCtxPtr = ExternalApplCtxPtr;
}

Children
  • 0 in reply to Øyvind Teig

    Here is the aseembly code:

    0x0004DD30  E5C4B0F0  STRB      R11,[R4,#0x00F0]
   735:                 ContextPtr->Byte_1     = 1;
0x0004DD34  E5C4030C  STRB      R0,[R4,#0x030C]
   736:                 ContextPtr->Byte_2     = 2;
0x0004DD38  E3A00002  MOV       R0,#0x00000002
0x0004DD3C  E5C4030D  STRB      R0,[R4,#0x030D]
   737:                 ContextPtr->Byte_3     = 3;
0x0004DD40  E3A00003  MOV       R0,#0x00000003
0x0004DD44  E5C40310  STRB      R0,[R4,#0x0310]
   738:                 ContextPtr->Byte_4     = 4;
0x0004DD48  E3A00004  MOV       R0,#0x00000004
   739:                 ContextPtr->Word_1     = 0xAA22;
0x0004DD4C  E59F1AA4  LDR       R1,[PC,#0x0AA4]
0x0004DD50  E5C40326  STRB      R0,[R4,#0x0326]
0x0004DD54  E2840C03  ADD       R0,R4,#0x00000300
0x0004DD58  E1C010BE  STRH      R1,[R0,#0x0E]
   740:                 ContextPtr->Word_2     = 0xBB33;
0x0004DD5C  E59F1A98  LDR       R1,[PC,#0x0A98]
0x0004DD60  E1C012B4  STRH      R1,[R0,#0x24]
   741:                 ContextPtr->Fence_1    = 0x12345678;
0x0004DD64  E59F0A94  LDR       R0,[PC,#0x0A94]
0x0004DD68  E5840314  STR       R0,[R4,#0x0314]
   742:                 ContextPtr->Fence_2    = 0x55AA6677;
0x0004DD6C  E59F0A90  LDR       R0,[PC,#0x0A90]
0x0004DD70  E5840318  STR       R0,[R4,#0x0318]
   743:                 ContextPtr->Address_1  = &(ContextPtr->Fence_1);
0x0004DD74  E2840FC5  ADD       R0,R4,#0x00000314
0x0004DD78  E584031C  STR       R0,[R4,#0x031C]
   744:                 ContextPtr->Address_2  = &(ContextPtr->Fence_2);
0x0004DD7C  E2840FC6  ADD       R0,R4,#0x00000318
0x0004DD80  E5840320  STR       R0,[R4,#0x0320]
   745:                 ExternalApplCtxPtr     = (ApplCtx_a*) MEM_ALLOC_F(sizeof(ApplCtx_a));
0x0004DD84  E3A00084  MOV       R0,#0x00000084
0x0004DD88  EB001661  BL        MemAlloc(0x00053714)
0x0004DD8C  E51F11C0  LDR       R1,[PC,#-0x01C0]
   746:                 ContextPtr->ApplCtxPtr = ExternalApplCtxPtr;

  • 0 in reply to Øyvind Teig

    What about ContextPtr? Is it aligned to a 4-byte boundary?

  • 0 in reply to Mik Kleshov

    ContextPtr 0x3c012d46 is 1006710086 and divided by 4 is 251677521,5 --- NO! ---

    So, I'd have to look at our malloc!
    Ported from AVR ATMega256 application!
    I have the code available!

    Thank you! I'll keep the list posted with the result!

    Øyvind Teig
    home.no.net/.../work.html

  • 0 in reply to Øyvind Teig

    Case closed!

    Our local "malloc" reimplemented to align on 4-byte boundary!

    Thank you very much!

    Øyvind Teig
    home.no.net/.../work.html