I’m working on running the Core Flight System with RTEMS6 on a Beaglebone Black using this repository rtems-cfs-demo for a personal project.

I’ve followed all the steps provided, and everything worked perfectly until I made some additional changes. I tried add a simple library for the run-time loader from this repository sample-lib.

PROBLEM

I encounter an error that I called “string shifting”, because I have never met this before. Some strings from other places get passed unreasonably into dev_mutex.c, where I made a system call OS_MutSemCreate (this is equal to rtems_semaphore_create or pthread_mutex_init). The error could happen to any function that received the string literal directly.

For example:

strncpy(SAMPLE_Buffer, "SaMpLe", sizeof(SAMPLE_Buffer))

#define SAMPLE_LIB_VERSION_STRING "Sample Lib DEVELOPMENT BUILD "

OS_printf("SAMPLE Lib Initialized.%sn", SAMPLE_LIB_VERSION_STRING);

Here is the console result when running the program on the board.

// fsw/mutex/dev_mutex.c

OS_MutSemCreate(0 - SaM): 0    /* The corrected string should be AAA */
OS_MutSemCreate(1 - Sam): 0    /* The corrected string should be AAB */
OS_MutSemCreate(2 - SAM): 0    /* The corrected string should be AAC */
OS_MutSemCreate(3 - AAD): 0
OS_MutSemCreate(4 - AAE): 0

WORKAROUND SOLUTION

After that I made some modifications for library above and it works properly. The modifications include avoiding using the string literal macro directly, but instead declare a pointer to point to these literals.

fsw/mutex/dev_mutex.c

const char *dev_strs[] = {"AAA", "AAB", "AAC", "AAD", "AAE", "AAF", "AAG", "AAH", "AAI", "AAJ", "AAK",
                          "AAL", "AAM", "AAN", "AAO", "AAP", "AAQ", "AAR", "AAS", "AAT", "AAU", "AAV",
                          "AAW", "AAX", "AAY", "AAZ", "ABA", "ABB", "ABC", "ABD", "ABE"};

static void getDeviceString(DeviceId id, char *deviceID)
{
    if (id >= DEV_0 && id <= DEV_30)
    {
        // In the sample_lib library, I pass the string literal macro directly
        CFE_PSP_MemCpy(deviceID, dev_strs[id], strlen(dev_strs[id])); // Abstraction of memcpy
        deviceID[strlen(dev_strs[id])] = '';
    }
    else
    {
        deviceID[0] = '';
    }
}

int32 mutexInitialize(MutexHandler_t *hwMutex, DeviceId ID)
{
    int32 Status = OS_SUCCESS;
    char  mutex_name[OS_MAX_API_NAME];
    char  deviceID[OS_MAX_API_NAME];

    CFE_PSP_MemSet(deviceID, 0, OS_MAX_API_NAME); // Abstraction of memset
    getDeviceString(ID, deviceID);

    if (deviceID == NULL)
    {
        return OS_ERROR;
    }

    CFE_PSP_MemSet(mutex_name, 0, OS_MAX_API_NAME);         // Abstraction of memset
    CFE_PSP_MemCpy(mutex_name, deviceID, strlen(deviceID)); // Abstraction of memcpy
    mutex_name[strlen(deviceID)] = '';

    Status = OS_MutSemCreate(&hwMutex->mutex, mutex_name, 0);

    printf("OS_MutSemCreate(%p - %s): %dn", (void *)mutex_name, mutex_name, Status);

    return Status;
}

QUESTION

Has anyone encountered a similar issue before? Any suggestions on where I should start investigating? Thank you in advance!