Re: [PATCH v6 1/6] printk: Save console options for add_preferred_console_match()

Andy Shevchenko
2024-02-13T16:42:05Z

On Tue, Feb 13, 2024 at 10:45:08AM +0200, Tony Lindgren wrote:
> Driver subsystems may need to translate the preferred console name to the
> character device name used. We already do some of this in console_setup()
> with a few hardcoded names, but that does not scale well.
>
> The console options are parsed early in console_setup(), and the consoles
> are added with __add_preferred_console(). At this point we don't know much
> about the character device names and device drivers getting probed.
>
> To allow driver subsystems to set up a preferred console, let's save the
> kernel command line console options. To add a preferred console from a
> driver subsystem with optional character device name translation, let's
> add a new function add_preferred_console_match().
>
> This allows the serial core layer to support console=DEVNAME:0.0 style
> hardware based addressing in addition to the current console=ttyS0 style
> naming. And we can start moving console_setup() character device parsing
> to the driver subsystem specific code.
>
> We use a separate array from the console_cmdline array as the character
> device name and index may be unknown at the console_setup() time. And
> eventually there's no need to call __add_preferred_console() until the
> subsystem is ready to handle the console.
>
> Adding the console name in addition to the character device name, and a
> flag for an added console, could be added to the struct console_cmdline.
> And the console_cmdline array handling could be modified accordingly. But
> that complicates things compared saving the console options, and then
> adding the consoles when the subsystems handling the consoles are ready.

...

> +int __init console_opt_save(const char *str, const char *brl_opt)
> +{
> + struct console_option *con;
> + const char *opt = NULL;
> + size_t namelen, optlen;
> + int i;

> + namelen = strcspn(str, ",");
> + if (!namelen)
> + return -EINVAL;
> +
> + optlen = strlen(str) - namelen;
> + if (optlen > 1)
> + opt = str + namelen + 1;
> +
> + if (namelen >= CONSOLE_NAME_MAX || optlen >= CONSOLE_OPT_MAX)
> + return -EINVAL;
> +
> + for (i = 0; i < MAX_CMDLINECONSOLES; i++) {
> + con = &conopt[i];
> +
> + if (con->name[0]) {
> + if (!strncmp(str, con->name, namelen))
> + return 0;
> + continue;
> + }

> + strscpy(con->name, str, namelen + 1);
> + if (opt)
> + strscpy(con->opt, opt, optlen + 1);

> + /* See _braille_console_setup(), both empty and NULL are valid */
> + if (brl_opt) {
> + strscpy(con->brl_opt, brl_opt, CONSOLE_BRL_OPT_MAX);
> + con->has_brl_opt = 1;
> + }
> +
> + return 0;
> + }
> +
> + return -ENOMEM;
> +}

With fresh look at the above, can we amend it like below?
(dropped NULL assignment, optimized strlen(), split checks, dropped unneeded +1 in strscpy() calls)

int __init console_opt_save(const char *str, const char *brl_opt)
{
struct console_option *con;
size_t namelen, optlen;
const char *opt;
int i;

namelen = strcspn(str, ",");
if (namelen == 0 || namelen >= CONSOLE_NAME_MAX)
return -EINVAL;

opt = str + namelen;
if (*opt == ',')
opt++;

optlen = strlen(opt);
if (optlen >= CONSOLE_OPT_MAX)
return -EINVAL;

for (i = 0; i < MAX_CMDLINECONSOLES; i++) {
con = &conopt[i];

if (con->name[0]) {
if (!strncmp(str, con->name, namelen))
return 0;
continue;
}

strscpy(con->name, str, namelen);
strscpy(con->opt, opt, optlen); // not sure if emptying opt is okay

/* See _braille_console_setup(), both empty and NULL are valid */
if (brl_opt) {
strscpy(con->brl_opt, brl_opt, CONSOLE_BRL_OPT_MAX);
con->has_brl_opt = 1;
}

return 0;
}

return -ENOMEM;
}

--
With Best Regards,
Andy Shevchenko