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@xxxxxxxxxx>
---
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
