[okl4-developer] MR registers corrupted when using L4_Send, L4_Receive

[Gabi Voiculescu]

Hi.

I am using okl4 2.1 (yes, I know it is a little old) on gumstix. 

I recently wanted to study IPC with MR exchange (passing information from one thread to the other). 

The existing iguana examples (like sleeping_barber) do not seem to be using the code sections of interest (for the default one barber and one consumer).

So I created my own example, and  used L4_Send(), L4_Receive() and L4_Wait(), while testing the obtained results using L4_MsgStore() and L4_MsgWord().

I saw that the MR registers were corrupted when I read them in the "thread", when comparing with "main".

I expected MR[0] would be different (different tag), but I don't understand why are the other ones different...
Is this because the inline L4_Send, L4_Receive change ARM gp registers before they call L4_Ipc?


Are the helper message functions broken (the inlines aren't designed to work with L4_Send, L4_Receive) in okl4 2.1 ?

Thank you,
Gabi Voiculescu

The Original file:

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>

#include <l4/thread.h>
#include <l4/ipc.h>

#include <iguana/thread.h>
#include <iguana/memsection.h>
#include <iguana/env.h>

static volatile L4_Thread_Id_t main_tid;


void thread(int argc, char** argv)
{
    L4_Msg_t msg;
    L4_MsgTag_t tag;
    L4_ThreadId_t from_tid;
    int i;
    L4_Word_t mr1;

....
    L4_MsgClear(&msg);
    L4_Set_MsgLabel(&msg, 0x12);

    L4_MsgLoad(&msg);
    //tag = L4_Receive(main_tid);
    tag = L4_Wait(&from_tid);

    L4_MsgStore(tag, &msg);

    if (L4_IpcFailed(tag)) {
        printf("Player thread error syncing with main (0x%lx) (%ld).\n", (long) from_tid.raw,
               (long) L4_ErrorCode() >> 1);
    }

    printf("\n\n");
    /* Get Information from MRs: register information is different than what I send !!!! */
    for (i=0; i<6; i++) {
        mr1 = L4_MsgWord(&msg, i);
        printf("Thread: mr[%d]=%lx\n", i, mr1);
    }
    printf("msg.tag.X.u = %d\n", msg.tag.X.u);
    printf("L4_Label(tag) = %lx\n", L4_Label(tag) );

    while(1);
....

}


int main(int argc, char **argv)
{
    L4_ThreadId_t from_tid, thread_tid[2];
    char thread_name[20];
    L4_Msg_t msg;
    L4_MsgTag_t tag;
    int i;
    L4_Word_t mr1;

    main_tid = thread_l4tid(env_thread(iguana_getenv("MAIN")));

    for (i=0; i<2; i++) {
        sprintf(&thread_name[0], "THREAD%d", i);
        thread_tid = thread_l4tid(env_thread(iguana_getenv(thread_name)));
    }

        L4_MsgClear(&msg);
        L4_Set_Label(&tag, (L4_Word_t) i);
        L4_Set_MsgLabel(&msg, i);
        L4_Set_MemoryCopy(&msg.tag);
        L4_Set_MsgTag(&msg.tag);
        &msg.tag.X.u=2;
        L4_MsgAppendWord(&msg, tag.raw);
        L4_MsgAppendWord(&msg, 0x1234); 
        L4_MsgAppendWord(&msg, 0x5678);          
        L4_MsgLoad(&msg);

        tag = L4_Send(thread_l4tid(thread_tid[i]));

        L4_MsgStore(tag, &msg);


        for (int j=0; j<6; j++) {
            mr1 = L4_MsgWord(&msg, j);
            printf("Main: Thread[%d]: mr[%d]=%lx\n", i, j, mr1);
        }
        printf("msg.tag.X.u = %d\n", msg.tag.X.u);

        while(1);
}

Gives me the result:
Main: Thread[0]: mr[0]=80801c40
Main: Thread[0]: mr[1]=fffffff8
Main: Thread[0]: mr[2]=ffffffff
Main: Thread[0]: mr[3]=1
Main: Thread[0]: mr[4]=0
Main: Thread[0]: mr[5]=80805c50
msg.tag.X.u = 0

Main: Thread[1]: mr[0]=80801c40
Main: Thread[1]: mr[1]=fffffff8
Main: Thread[1]: mr[2]=ffffffff
Main: Thread[1]: mr[3]=1
Main: Thread[1]: mr[4]=0
Main: Thread[1]: mr[5]=80805c50
msg.tag.X.u = 0


Thread: mr[0]=20001
Thread: mr[1]=8002c0b8
Thread: mr[2]=0    <---notice change from here on
Thread: mr[3]=0
Thread: mr[4]=0
Thread: mr[5]=0
msg.tag.X.u = 2

Thread: mr[0]=24001
Thread: mr[1]=8002c048
Thread: mr[2]=0
Thread: mr[3]=0
Thread: mr[4]=0
Thread: mr[5]=0
msg.tag.X.u = 2
L4_Label(tag) = 0

L4_Label(tag) = 0






      
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