Thread: Accessing a physical memory address

  1. #1
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    Accessing a physical memory address

    Hi

    I want to read and write from a physical memory, the method I used is
    ex: if memory address is 0x58000000
    int a = 10;
    int b;
    * (volatile int * ) 0x58000000 = a;
    b = *( volatile int * ) 0x58000000;
    printf( " %d ", b );

    in this way I am getting segmentation fault. What is right way to do this operation.

    Thanks

  2. #2
    and the hat of int overfl Salem's Avatar
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    You don't have access to physical memory unless you're deep in the kernel.

    Normal user-space programs get given virtual memory by the kernel, and it's the kernel that's responsible for mapping virtual memory to physical memory.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

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    Quote Originally Posted by Salem View Post
    You don't have access to physical memory unless you're deep in the kernel.

    Normal user-space programs get given virtual memory by the kernel, and it's the kernel that's responsible for mapping virtual memory to physical memory.
    Actually, I am working on a SoC which has Cortex R52 as real time core and Cortex A76 as application core and yocto Linux is running on that. I want to read value from the Linux side from a shared memory address, the value is written by R52.How can I do that

  4. #4
    and the hat of int overfl Salem's Avatar
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    Then you need to write yourself a little kernel driver to run on the A76.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

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