LPC 1769(cortex m3) Code Red IDE---No source available for g_pfnVectors() at0x0

Question

I am trying to call a SVC from user mode with stack PSP . I observe the following error on debugging a code on LPC 1769(cortex m3)------- No source available for "g_pfnVectors() at 0x0" The IDE which I am using is CODE RED LPC Xpresso with LPC 1769 from Embedded Artists.

Here is the assembly code

        .syntax unified
        .cpu cortex-m3
        .thumb
        .align 2
        .global Start
        .thumb
        .thumb_func
    Start:
//  LDR r0,=0xf00d   //initial value of r0 which has to be changed in svc handler
    PUSH {lr}


    MOV r0,#0x2      // set stack to PSP now. Set CONTROL[1]=1
    MSR CONTROL,r0
    ISB              // Instruction memory barrier – ensures that the above is executed


    MOV r0,#0x3         //change to user level
    MSR CONTROL, r0
    ISB

    MOV r0,#0x2
    MOV r2,#0x2
exp:
    MUL r0,r0
    SUBS r2,#1
    BNE exp

    SVC 1 //print in hex

    MOV r0,#0x4  //print in decimal
    SVC 2

    MOV r0,#'A'
    SVC 3         //print character

    MOV r1,0x0
    MSR CONTROL,r1
             ISB


    POP {lr}
    BX lr

inside SVC, I do the stack check and corresponding functions are called for printing on console. here is the SVC code:

__attribute__ ((section(".after_vectors")))
void SVCall_Handler(void)
{
  while(1)
  {
    __asm(
            "TST lr, #4         \n"
            "ITE eq         \n"
            "MRSEQ r0, MSP      \n"
            "MRSNE r0, PSP      \n"
            "LDR r0,[r0,#0]     \n"
            "LDR r1, [r0, #24]  \n"
            "LDRB r1, [r1, #-2] \n"
            //immediate data in r1 and input parameter in r0

            //"PUSH {LR}            \n"
            "CBNZ r1,svc_hex            \n"
            "B svc_end          \n"

            "svc_hex:           \n"
            "CMP r1,#1          \n"
            "BNE svc_decimal             \n"
            " BL printhex               \n"
            "B svc_end          \n"

            "svc_decimal:               \n"
            "CMP r1,#2          \n"
            "BNE svc_character          \n"
            "BL printdecimal            \n"
            "B svc_end          \n"

            "svc_character:              \n"
            "CMP r1,#3          \n"
            "BL printcharacter          \n"
            "B svc_end          \n"

            "svc_end:           \n"
            "MOV r0,#0x0                \n"
            "MSR CONTROL,r0             \n"
            "ISB                \n"
            "BX LR              \n"
    );
  }
}

The printhex/printcaharacter/printdecimal are functions for printing the respective values on the console.

During debug, single step mode, after the SVC instruction, there is the error No source available for "g_pfnVectors() at 0x0" .

The cause and arrival of error is quite unexpected. is there any problem with the gdb debugger or is the way I am interpreting the code wrong?

score 2 · Answer 1 · answered Apr 10 '13 at 16:15

2

This might be a bit late for you, but maybe it's useful for somebody else.

g_pfnVectors (or whatever is at position 0x0), is the interrupt/exception vector table. SVC would call the SVC exception, a pointer to its function should be in the g_pfnVectors. It appears that is not the case in your code, so PC jumps to the 0x0, which is incidentally also g_pfnVectors.

answered Apr 10 '13 at 16:15

domen

1,819
12
19

thanks a lot. Can you please take a look at this-- http://stackoverflow.com/questions/15542360/pass-by-reference-in-assembly – gst Apr 10 '13 at 17:22

LPC 1769(cortex m3) Code Red IDE---No source available for g_pfnVectors() at0x0

1 Answers1