qnx get resmgr_context_t of old resource manager

Question

I trying to create my own process manager for qnx 6.6 over /proc/{pid}/as.

But I need to change only one operation (io_open), all other operations should continue work with old file (/proc/{pid}/as).

Can I just get pointer to resmgr_context_t (from path or fd, before resmgr_attach) and for all other operations just call default function?

This is stupied example of what I want:

resmgr_context_t* old_context;
int my_lseek(resmgr_context_t *ctp, io_lseek_t *msg, RESMGR_OCB_T *ocb){
   return iofunc_lseek_default(old_context, msg, ocb);
}

score 0 · Accepted Answer · answered Sep 26 '17 at 14:30

You need to make a regular resource manager that only registers a function for io_open, all other resource manager operations will filter down to the lower resource managers in the stack.

Return ENOENT from the io_open callback if you want the message to move down the resmgr stack to other registered io_open callbacks, otherwise return EOK.

Error checking was omitted for brevity.

#include <errno.h>
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <sys/iofunc.h>
#include <sys/dispatch.h>

static resmgr_connect_funcs_t    connect_funcs;
static resmgr_io_funcs_t         io_funcs;
static iofunc_attr_t             attr;

int io_open (resmgr_context_t *ctp, io_open_t  *msg, RESMGR_HANDLE_T *handle, void *extra);

int main(int argc, char **argv)
{
    resmgr_attr_t        resmgr_attr;
    dispatch_t           *dpp;
    dispatch_context_t   *ctp;
    int                  id;

    // initialize dispatch interface
    dpp = dispatch_create();

    // initialize resource manager attributes 
    memset(&resmgr_attr, 0, sizeof resmgr_attr);
    resmgr_attr.nparts_max = 1;
    resmgr_attr.msg_max_size = 2048;

    // initialize functions for handling messages 
    iofunc_func_init(_RESMGR_CONNECT_NFUNCS, &connect_funcs, 
                 _RESMGR_IO_NFUNCS, &io_funcs);
    connect_funcs.open = io_open;

    // initialize attribute structure used by the device 
    iofunc_attr_init(&attr, S_IFNAM | 0666, 0, 0);

    // attach to /proc/{pid}/as path, replace '1' with correct pid 
    resmgr_attach(dpp, &resmgr_attr,"/proc/1/as", 
        _FTYPE_ANY, _RESMGR_FLAG_BEFORE|_RESMGR_FLAG_DIR,
        &connect_funcs, &io_funcs, &attr);

    ctp = dispatch_context_alloc(dpp);

    /* start the resource manager message loop */
    while(1) {
        if((ctp = dispatch_block(ctp)) == NULL) {
            perror("dispatch_block");
            return EXIT_FAILURE;
        }
        dispatch_handler(ctp);
    }
}

int io_open (resmgr_context_t *ctp, io_open_t *msg, RESMGR_HANDLE_T *handle, void *extra)
{
    time_t tod;  
    tod = time(NULL); 
    printf ("%10d %-32s is being opened\n", tod, msg->connect.path);

    return(ENOENT);
}

"all other resource manager operations will filter down to the lower resource managers in the stack." Does It means, If I'll mmap callback, it will never triggered, cuz all msg after return ENOENT in io_open will be filtered down to the lower RM? — Alexandr Alexandrov, Oct 04 '17 at 12:47

qnx get resmgr_context_t of old resource manager

1 Answers1