Messages in this thread | | | Subject | Re: [PATCH v2 1/7] cmdline: Add generic function to build command line. | From | Christophe Leroy <> | Date | Wed, 3 Mar 2021 18:38:16 +0100 |
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Le 03/03/2021 à 18:28, Will Deacon a écrit : > On Tue, Mar 02, 2021 at 05:25:17PM +0000, Christophe Leroy 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. >> >> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> >> --- >> include/linux/cmdline.h | 62 +++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 62 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..ae3610bb0ee2 >> --- /dev/null >> +++ b/include/linux/cmdline.h >> @@ -0,0 +1,62 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +#ifndef _LINUX_CMDLINE_H >> +#define _LINUX_CMDLINE_H >> + >> +static __always_inline size_t cmdline_strlen(const char *s) >> +{ >> + const char *sc; >> + >> + for (sc = s; *sc != '\0'; ++sc) >> + ; /* nothing */ >> + return sc - s; >> +} >> + >> +static __always_inline size_t cmdline_strlcat(char *dest, const char *src, size_t count) >> +{ >> + size_t dsize = cmdline_strlen(dest); >> + size_t len = cmdline_strlen(src); >> + size_t res = dsize + len; >> + >> + /* This would be a bug */ >> + if (dsize >= count) >> + return count; >> + >> + dest += dsize; >> + count -= dsize; >> + if (len >= count) >> + len = count - 1; >> + memcpy(dest, src, len); >> + dest[len] = 0; >> + return res; >> +} > > Why are these needed instead of using strlen and strlcat directly?
Because on powerpc (at least), it will be used in prom_init, it is very early in the boot and KASAN shadow memory is not set up yet so calling generic string functions would crash the board.
> >> +/* >> + * This function will append 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. >> + * @dest: The destination of the final appended/prepended string. >> + * @src: The starting string or NULL if there isn't one. Must not equal dest. >> + * @length: the length of dest buffer. >> + */ >> +static __always_inline void cmdline_build(char *dest, const char *src, size_t length) >> +{ >> + if (length <= 0) >> + return; >> + >> + dest[0] = 0; >> + >> +#ifdef CONFIG_CMDLINE >> + if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !src || !src[0]) { >> + cmdline_strlcat(dest, CONFIG_CMDLINE, length); >> + return; >> + } >> +#endif > > CONFIG_CMDLINE_FORCE implies CONFIG_CMDLINE, and even if it didn't, > CONFIG_CMDLINE is at worst an empty string. Can you drop the #ifdef?
Ah yes, since cbe46bd4f510 ("powerpc: remove CONFIG_CMDLINE #ifdef mess") it is feasible. I can change that now.
> >> + if (dest != src) >> + cmdline_strlcat(dest, src, length); >> +#ifdef CONFIG_CMDLINE >> + if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && sizeof(CONFIG_CMDLINE) > 1) >> + cmdline_strlcat(dest, " " CONFIG_CMDLINE, length); >> +#endif > > Likewise, but also I'm not sure why the sizeof() is required.
It is to avoid adding a white space at the end of the command line when CONFIG_CMDLINE is empty. But maybe it doesn't matter ?
Christophe
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