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Commit e520d036 authored by Jay Freeman (saurik)'s avatar Jay Freeman (saurik)
Browse files

Added support for loop@/path/to/filename to init's mount. 

In keeping with the pattern of mtd@partition, I have added loop@path as a way to specify a loopback device. This way you can do things like mount directories in /system using cramfs from a file otherwise on /system (just one example oof how I'm using it). I specifically went with loop@ rather than adding this feature as a flag as the flags system is designed to set bits in the flags argument to mount: using loop@ fit the model in a much simpler manner and actually feels "correct".

This is a better version of the previously submitted 4045 that also refactors the mtd@ case. The reason for this is that I received comments that I should check for errors and return errors rather that do work in the case of success and fall through, but the mtd@ case wasn't doing that either and it became awkward to design the function so that it was half in one style of error handling and half in another. I also made certain to use inequality comparisons for Unix's -1 error returns rather than checking for -1, refactored my large if statement so as not to have danling parentheses, and disassocited the loop device on mount failure.
parent abb9638e

init/builtins.c

+61 −5
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ 
#include <stdlib.h>

#include <sys/mount.h>

#include <sys/resource.h>

#include <linux/loop.h>



#include "init.h"

#include "keywords.h"
@@ -231,7 +232,7 @@ static struct { 
int do_mount(int nargs, char **args)

{

    char tmp[64];

    char *source;

    char *source, *target, *system;

    char *options = NULL;

    unsigned flags = 0;

    int n, i;
@@ -249,15 +250,70 @@ int do_mount(int nargs, char **args) 
            options = args[n];

    }



    system = args[1];

    source = args[2];

    target = args[3];



    if (!strncmp(source, "mtd@", 4)) {

        n = mtd_name_to_number(source + 4);

        if (n >= 0) {

        if (n < 0) {

            return -1;

        }



        sprintf(tmp, "/dev/block/mtdblock%d", n);

            source = tmp;



        if (mount(tmp, target, system, flags, options) < 0) {

            return -1;

        }



        return 0;

    } else if (!strncmp(source, "loop@", 5)) {

        int mode, loop, fd;

        struct loop_info info;



        mode = (flags & MS_RDONLY) ? O_RDONLY : O_RDWR;

        fd = open(source + 5, mode);

        if (fd < 0) {

            return -1;

        }



        for (n = 0; ; n++) {

            sprintf(tmp, "/dev/block/loop%d", n);

            loop = open(tmp, mode);

            if (loop < 0) {

                return -1;

            }



            /* if it is a blank loop device */

            if (ioctl(loop, LOOP_GET_STATUS, &info) < 0 && errno == ENXIO) {

                /* if it becomes our loop device */

                if (ioctl(loop, LOOP_SET_FD, fd) >= 0) {

                    close(fd);



                    if (mount(tmp, target, system, flags, options) < 0) {

                        ioctl(loop, LOOP_CLR_FD, 0);

                        close(loop);

                        return -1;

                    }



                    close(loop);

                    return 0;

                }

            }



            close(loop);

        }



        close(fd);

        ERROR("out of loopback devices");

        return -1;

    } else {

        if (mount(source, target, system, flags, options) < 0) {

            return -1;

        }



        return 0;

    }

    return mount(source, args[3], args[1], flags, options);

}



int do_setkey(int nargs, char **args)