Re: [PATCH v2 1/7] cmdline: Add generic function to build command line.
From: Will Deacon <will@kernel.org>
Date: 2021-03-03 20:56:09
Also in:
linux-arch, linux-devicetree, lkml
On Tue, Mar 02, 2021 at 05:25:17PM +0000, Christophe Leroy wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- include/linux/cmdline.h | 62 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 include/linux/cmdline.hdiff --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?
+/*
+ * 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;
+ }
+#endifCONFIG_CMDLINE_FORCE implies CONFIG_CMDLINE, and even if it didn't, CONFIG_CMDLINE is at worst an empty string. Can you drop the #ifdef?
+ 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. Will