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

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Message-ID: <58834b01-aad5-fa1e-554e-6417b2357202@csgroup.eu>
Date:   Fri, 26 Mar 2021 16:55:31 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Rob Herring <robh@...nel.org>
Cc:     Will Deacon <will@...nel.org>, Daniel Walker <danielwa@...co.com>,
        Daniel Gimpelevich <daniel@...pelevich.san-francisco.ca.us>,
        "open list:GENERIC INCLUDE/ASM HEADER FILES" 
        <linux-arch@...r.kernel.org>, devicetree@...r.kernel.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        microblaze <monstr@...str.eu>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        nios2 <ley.foon.tan@...el.com>,
        Openrisc <openrisc@...ts.librecores.org>,
        linux-hexagon@...r.kernel.org,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        X86 ML <x86@...nel.org>, linux-xtensa@...ux-xtensa.org,
        SH-Linux <linux-sh@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>
Subject: Re: [PATCH v3 01/17] cmdline: Add generic function to build command
 line.



Le 26/03/2021 à 16:42, Rob Herring a écrit :
> On Fri, Mar 26, 2021 at 7:44 AM Christophe Leroy
> <christophe.leroy@...roup.eu> 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@ghiti.fr/
> 
> 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@...roup.eu>
>> ---
>> 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