Re: [PATCH v3 01/17] cmdline: Add generic function to build command line.

[Christophe Leroy]

Le 26/03/2021 à 16:42, Rob Herring a écrit :
> On Fri, Mar 26, 2021 at 7:44 AM Christophe Leroy
> <christophe.leroy@xxxxxxxxxx> wrote:
> > This code provides architectures with a way to build command line
> > based on what is built in the kernel and what is handed over by the
> > bootloader, based on selected compile-time options.
>
> Note that I have this patch pending:
>
> https://patchwork.ozlabs.org/project/devicetree-bindings/patch/20210316193820.3137-1-alex@xxxxxxxx/
>
> It's going to need to be adapted for this. I've held off applying to
> see if this gets settled.

good point.

Hope we can't have things like

	option="beautiful weather"

> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> > ---
> > v3:
> > - Addressed comments from Will
> > - Added capability to have src == dst
> > ---
> >   include/linux/cmdline.h | 57 +++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 57 insertions(+)
> >   create mode 100644 include/linux/cmdline.h
> >
> > diff --git a/include/linux/cmdline.h b/include/linux/cmdline.h
> > new file mode 100644
> > index 000000000000..dea87edd41be
> > --- /dev/null
> > +++ b/include/linux/cmdline.h
> > @@ -0,0 +1,57 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef _LINUX_CMDLINE_H
> > +#define _LINUX_CMDLINE_H
> > +
> > +#include <linux/string.h>
> > +
> > +/* Allow architectures to override strlcat, powerpc can't use strings so early */
> > +#ifndef cmdline_strlcat
> > +#define cmdline_strlcat strlcat
> > +#endif
> > +
> > +/*
> > + * This function will append or prepend a builtin command line to the command
> > + * line provided by the bootloader. Kconfig options can be used to alter
> > + * the behavior of this builtin command line.
> > + * @dst: The destination of the final appended/prepended string.
> > + * @src: The starting string or NULL if there isn't one.
> > + * @len: the length of dest buffer.
> > + */
> > +static __always_inline void __cmdline_build(char *dst, const char *src, size_t len)
> > +{
> > +       if (!len || src == dst)
> > +               return;
> > +
> > +       if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !src) {
> > +               dst[0] = 0;
> > +               cmdline_strlcat(dst, CONFIG_CMDLINE, len);
> > +               return;
> > +       }
> > +
> > +       if (dst != src)
> > +               dst[0] = 0;
> > +
> > +       if (IS_ENABLED(CONFIG_CMDLINE_PREPEND))
> > +               cmdline_strlcat(dst, CONFIG_CMDLINE " ", len);
> > +
> > +       cmdline_strlcat(dst, src, len);
> > +
> > +       if (IS_ENABLED(CONFIG_CMDLINE_EXTEND))
>
> Should be APPEND.

Not yet. For the time being all architectures use EXTEND only.

In patch 3 it is changed to:

-	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND))
+	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) || IS_ENABLED(CONFIG_CMDLINE_APPEND))

Then in last patch, I forgot but I should have done:

-	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) || IS_ENABLED(CONFIG_CMDLINE_APPEND))
+	if (IS_ENABLED(CONFIG_CMDLINE_APPEND))


> > +               cmdline_strlcat(dst, " " CONFIG_CMDLINE, len);
> > +}
> > +
> > +#define cmdline_build(dst, src, len) do {                              \
>
> Perhaps a comment why we need this to be a define.

Probably we don't need anymore as I finally decided to use COMMAND_LINE_SIZE instead of 'len' as the 
size of the temporary buffer.

> > +       char *__c_dst = (dst);                                          \
> > +       const char *__c_src = (src);                                    \
> > +                                                                       \
> > +       if (__c_src == __c_dst) {                                       \
> > +               static char __c_tmp[COMMAND_LINE_SIZE] __initdata = ""; \
> > +                                                                       \
> > +               cmdline_strlcat(__c_tmp, __c_src, COMMAND_LINE_SIZE);   \
> > +               __cmdline_build(__c_dst, __c_tmp, (len));               \
> > +       } else {                                                        \
> > +               __cmdline_build(__c_dst, __c_src, (len));               \
> > +       }                                                               \
> > +} while (0)
> > +
> > +#endif /* _LINUX_CMDLINE_H */
> > --
> > 2.25.0

Christophe