CODEWITHSUNDEEP
clinuxshared-memoryheap-memory
Mohit Sharma
Mohit Sharma

Reputation: 348

Reading memory of another process in C without ptrace in linux

I am trying to read memory of another process and print whatever is in the memory (Heap and/or stack). I have got the range of memory addresses using /proc I have extracted address range like this. Now I want to read the memory range of the other process like as defined.

5569032d2000-5569032f3000 rw-p 00000000 00:00 0 [heap]

I am stuck on how to access those memory addresses. I tried something like shown below , but doesn't help much.

int main(int argc, char *argv[]) {

off_t offset = strtoul(argv[1], NULL, 0);
size_t len = strtoul(argv[2], NULL, 0);

// Truncate offset to a multiple of the page size, or mmap will fail.
size_t pagesize = sysconf(_SC_PAGE_SIZE);
off_t page_base = (offset / pagesize) * pagesize;
off_t page_offset = offset - page_base;

int fd = open("/dev/mem", O_SYNC);
unsigned char *mem = mmap(NULL, page_offset + len, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, page_base);
if (mem == MAP_FAILED) {
    perror("Can't map memory");
    return -1;
}

size_t i;
for (i = 0; i < len; ++i)
    printf("%x ", (int)mem[page_offset + i]);
//size_t i;
return 0;}

Thanks.

I am making like a debug tool for my embedded system. I can't use ptrace() as it halts the running process while trying to peek into the device memory.

Upvotes: 0

Views: 1610

Answers (1)

Mohit Sharma
Mohit Sharma

Reputation: 348

I figured out to read the process of another process, I can use process_vm_readv() function as follow:


pid_t pid; // Put value of pid in this
void *remotePtr; // Put starting address 
size_t bufferLength; // Put size of buffer in this, aka size to read
// Build iovec structs
    struct iovec local[1];
    local[0].iov_base = calloc(bufferLength, sizeof(char));
    local[0].iov_len = bufferLength;

    struct iovec remote[1];
    remote[0].iov_base = remotePtr;
    remote[0].iov_len = bufferLength;

/*Nread will contain amount of bytes of data read*/

nread = process_vm_readv(pid, local, 2, remote, 1, 0); 
    if (nread < 0) {
        switch (errno) {
        case EINVAL:
            printf("ERROR: INVALID ARGUMENTS.\n");
            break;
        case EFAULT:
            printf
                ("ERROR: UNABLE TO ACCESS TARGET MEMORY ADDRESS.\n");
            break;
        case ENOMEM:
            printf("ERROR: UNABLE TO ALLOCATE MEMORY.\n");
            break;
        case EPERM:
            printf
                ("ERROR: INSUFFICIENT PRIVILEGES TO TARGET PROCESS.\n");
            break;
        case ESRCH:
            printf("ERROR: PROCESS DOES NOT EXIST.\n");
            break;
        default:
            printf("ERROR: AN UNKNOWN ERROR HAS OCCURRED.\n");
        }

        return -1;
    }
/* To print the read data */
printf("The read text is \n %s\n", local[0].iov_base);

Upvotes: 2

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