Commit 6407d76e authored by Gabriel L. Somlo's avatar Gabriel L. Somlo Committed by Gerd Hoffmann
Browse files

fw_cfg: insert string blobs via qemu cmdline 



Allow users to provide custom fw_cfg blobs with ascii string
payloads specified directly on the qemu command line.

Suggested-by: default avatarJordan Justen <jordan.l.justen@intel.com>
Suggested-by: default avatarLaszlo Ersek <lersek@redhat.com>
Signed-off-by: default avatarGabriel Somlo <somlo@cmu.edu>
Message-id: 1443544141-26568-1-git-send-email-somlo@cmu.edu
Reviewd-by: default avatarLaszlo Ersek <lersek@redhat.com>
Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
parent 526d5809

docs/specs/fw_cfg.txt

+15 −0
Original line number Diff line number Diff line
@@ -216,6 +216,21 @@ the following syntax: 
where <item_name> is the fw_cfg item name, and <path> is the location

on the host file system of a file containing the data to be inserted.



Small enough items may be provided directly as strings on the command

line, using the syntax:



    -fw_cfg [name=]<item_name>,string=<string>



The terminating NUL character of the content <string> will NOT be

included as part of the fw_cfg item data, which is consistent with

the absence of a NUL terminator for items inserted via the file option.



Both <item_name> and, if applicable, the content <string> are passed

through by QEMU without any interpretation, expansion, or further

processing. Any such processing (potentially performed e.g., by the shell)

is outside of QEMU's responsibility; as such, using plain ASCII characters

is recommended.



NOTE: Users *SHOULD* choose item names beginning with the prefix "opt/"

when using the "-fw_cfg" command line option, to avoid conflicting with

item names used internally by QEMU. For instance:

qemu-options.hx

+6 −1
Original line number Diff line number Diff line
@@ -2724,13 +2724,18 @@ ETEXI 


DEF("fw_cfg", HAS_ARG, QEMU_OPTION_fwcfg,

    "-fw_cfg [name=]<name>,file=<file>\n"

    "                add named fw_cfg entry from file\n",

    "                add named fw_cfg entry from file\n"

    "-fw_cfg [name=]<name>,string=<str>\n"

    "                add named fw_cfg entry from string\n",

    QEMU_ARCH_ALL)

STEXI

@item -fw_cfg [name=]@var{name},file=@var{file}

@findex -fw_cfg

Add named fw_cfg entry from file. @var{name} determines the name of

the entry in the fw_cfg file directory exposed to the guest.



@item -fw_cfg [name=]@var{name},string=@var{str}

Add named fw_cfg entry from string.

ETEXI



DEF("serial", HAS_ARG, QEMU_OPTION_serial, \

vl.c

+27 −6
Original line number Diff line number Diff line
@@ -512,6 +512,10 @@ static QemuOptsList qemu_fw_cfg_opts = { 
            .type = QEMU_OPT_STRING,

            .help = "Sets the name of the file from which\n"

                    "the fw_cfg blob will be loaded",

        }, {

            .name = "string",

            .type = QEMU_OPT_STRING,

            .help = "Sets content of the blob to be inserted from a string",

        },

        { /* end of list */ }

    },
@@ -2239,11 +2243,16 @@ char *qemu_find_file(int type, const char *name) 
    return NULL;

}



static inline bool nonempty_str(const char *str)

{

    return str && *str;

}



static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp)

{

    gchar *buf;

    size_t size;

    const char *name, *file;

    const char *name, *file, *str;



    if (opaque == NULL) {

        error_report("fw_cfg device not available");
@@ -2251,8 +2260,15 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp) 
    }

    name = qemu_opt_get(opts, "name");

    file = qemu_opt_get(opts, "file");

    if (name == NULL || *name == '\0' || file == NULL || *file == '\0') {

        error_report("invalid argument value");

    str = qemu_opt_get(opts, "string");



    /* we need name and either a file or the content string */

    if (!(nonempty_str(name) && (nonempty_str(file) || nonempty_str(str)))) {

        error_report("invalid argument(s)");

        return -1;

    }

    if (nonempty_str(file) && nonempty_str(str)) {

        error_report("file and string are mutually exclusive");

        return -1;

    }

    if (strlen(name) > FW_CFG_MAX_FILE_PATH - 1) {
@@ -2263,10 +2279,15 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp) 
        error_report("WARNING: externally provided fw_cfg item names "

                     "should be prefixed with \"opt/\"!");

    }

    if (nonempty_str(str)) {

        size = strlen(str); /* NUL terminator NOT included in fw_cfg blob */

        buf = g_memdup(str, size);

    } else {

        if (!g_file_get_contents(file, &buf, &size, NULL)) {

            error_report("can't load %s", file);

            return -1;

        }

    }

    fw_cfg_add_file((FWCfgState *)opaque, name, buf, size);

    return 0;

}