I have a problem with linking class to specific memory region via Linker Script

I've figure out how to link variables and functions that are out of the class but I have no idea how to link the class into the memory region specified in the linker script

My linker script is very simple:

SECTIONS
{
  . = 0x1000000;
  .text : { *(.text) }
  . = 0x8000000;
  .data : { *(.data) }
  .bss : { *(.bss) }
}

And the main code:

#include <iostream>     // system
#include "mem.h"

using namespace std;

unsigned int A = 0xFFFF1234;
unsigned int B = 0x00001234;

void Function_A(void)
{
    printf("This is execution of the void Function A \n");
}

void Function_B(int x)
{
    x = x   1;
    printf("This is execution of the void Function B with variable x:%d \n",x);
}

int main(int argc, char* argv[]) 
{
    system("clear");

    unsigned int * pA = &A;
    unsigned int * pB = &B;

    printf("Original Data A ---> 0xx\n",A);
    printf("Original Data B ---> 0xx\n\n",B);

    printf("Pointer to A variable ---> %p\n",pA);
    printf("Pointer to B variable ---> %p\n\n",pB);

    void (*pFunction_A)(void) = &Function_A;
    void (*pFunction_B)(int)  = &Function_B;

    MemAssembly * pMemAssembly;
    pMemAssembly->MemDump();

    // Testing function pointers
    pFunction_A();
    pFunction_B(100);
    (*pFunction_B)(200);

    printf("Pointer to Function_A ---> %p\n",pFunction_A);
    printf("Pointer to Function_B ---> %p\n\n",pFunction_B);
    
    // Address is not linked !!!????
    printf("Pointer to MemAssembly Class ---> %p\n\n",pMemAssembly);

    return 0;
}

Now, when I execute I get this:

Original Data A ---> 0xffff1234
Original Data B ---> 0x00001234

Pointer to A variable ---> 0x8000004
Pointer to B variable ---> 0x8000008

RAX_Accumulator ---> Read A : 0x00000000ffff1234 
RAX_Accumulator ---> Read B : 0x0000000000001234 

This is execution of the void Function A 
This is execution of the void Function B with variable x:101 
This is execution of the void Function B with variable x:201 
Pointer to Function_A ---> 0x10000e9
Pointer to Function_B ---> 0x1000103

Pointer to MemAssembly Class ---> 0x7f282ab46764

The mem.h looks as follows:

#ifndef MEM_H
#define MEM_H

#include <inttypes.h>

extern "C" unsigned long _MEMORY_READ_A(void);
extern "C" unsigned long _MEMORY_READ_B(void);


class MemAssembly{

    public:
        MemAssembly();
        ~MemAssembly();
        
        int AssemblyMemoryDump(void);

        void MemDump(void)
        { 
            printf("RAX_Accumulator ---> Read A : %#018" PRIx64 " \n",_MEMORY_READ_A());
            printf("RAX_Accumulator ---> Read B : %#018" PRIx64 " \n\n",_MEMORY_READ_B());
        }

};

#endif /* MEM_H */

And the assemblies

section .text

global _MEMORY_READ_A
_MEMORY_READ_A:
    mov eax, [0x08000000   4]
    ret

global _MEMORY_READ_B
_MEMORY_READ_B:
    mov eax, [0x08000000   8]
    ret

So my question is: How should I modify linker script, mem.h or the assemblies in order to load my class into specific memory region rather than using dynamic allocation ???

Instead of this one:

Pointer to MemAssembly Class ---> 0x7f282ab46764

Read address specified in the linker script ???

CodePudding user response：

Thanks Peter for the help

Here what I did:

Added MemAssembly section in ASM

section .MemAssembly

    global global_MemAssembly
    global_MemAssembly:

Link it with 0xb000000

SECTIONS
{
  . = 0x1000000;
  .text : { *(.text) }
  . = 0x8000000;
  .data : { *(.data) }
  .bss : { *(.bss) }
  . = 0xB000000;
  .MemAssembly : { *(MemAssembly)}
}

Using Test class

class MemAssembly{

    public:
        MemAssembly();
        ~MemAssembly();
        
        int x,y,z,t;
        long a,b,c,d;
        long long dx,dy,dz,dt;

        void MemDump(void)
        {
            printf("x  ---> %p y  ---> %p z  ---> %p t  ---> %p\n", &x, &y, &z, &t);
            printf("a  ---> %p b  ---> %p c  ---> %p d  ---> %p\n", &a, &b, &c, &d);
            printf("dx ---> %p dy ---> %p dz ---> %p dt ---> %p\n\n", &dx, &dy, &dz, &dt);
        }
};

When I call MemDump() using usign dynamic:

MemAssembly * pMemAssembly

I get:

x  ---> 0x7ffd7cc36040 y  ---> 0x7ffd7cc36044 z  ---> 0x7ffd7cc36048 t  ---> 0x7ffd7cc3604c
a  ---> 0x7ffd7cc36050 b  ---> 0x7ffd7cc36058 c  ---> 0x7ffd7cc36060 d  ---> 0x7ffd7cc36068
dx ---> 0x7ffd7cc36070 dy ---> 0x7ffd7cc36078 dz ---> 0x7ffd7cc36080 dt ---> 0x7ffd7cc36088

But when I've used:

extern MemAssembly global_MemAssembly;
MemAssembly * pMemAssembly = &global_MemAssembly;

I get:

x  ---> 0xb000000 y  ---> 0xb000004 z  ---> 0xb000008 t  ---> 0xb00000c
a  ---> 0xb000010 b  ---> 0xb000018 c  ---> 0xb000020 d  ---> 0xb000028
dx ---> 0xb000030 dy ---> 0xb000038 dz ---> 0xb000040 dt ---> 0xb000048

Which is what I've expected