[PATCH 18/28] LoongArch: Refactor bootcmdline_init() to use seq_buf instead of strlcat()

[Bill Wendling]

bootcmdline_init() uses multiple strlcat() calls to append
init_command_line or CONFIG_CMDLINE to boot_command_line.

In preparation for removing the deprecated strlcat() API[1], initialize a
struct seq_buf with the existing contents of boot_command_line and use
seq_buf_puts() to append the command line fragments.

Link: https://github.com/KSPP/linux/issues/370 [1]
Cc: codemender-patching+linux@xxxxxxxxxx
Assisted-by: CoPilot:1.0 [shell_command_run, editor_update_file, make_kernel_build_single_file]
Signed-off-by: Bill Wendling <morbo@xxxxxxxxxx>
---
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Huacai Chen <chenhuacai@xxxxxxxxxx>
Cc: WANG Xuerui <kernel@xxxxxxxxxx>
Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Cc: "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: Helge Deller <deller@xxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
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---
 arch/loongarch/kernel/setup.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 6fa4a22a58fd..826396f141b9 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -33,6 +33,7 @@
 #include <linux/of_address.h>
 #include <linux/suspend.h>
 #include <linux/swiotlb.h>
+#include <linux/seq_buf.h>
 
 #include <asm/addrspace.h>
 #include <asm/alternative.h>
@@ -305,6 +306,8 @@ static void __init fdt_setup(void)
 
 static void __init bootcmdline_init(char **cmdline_p)
 {
+	struct seq_buf s;
+
 	/*
 	 * If CONFIG_CMDLINE_FORCE is enabled then initializing the command line
 	 * is trivial - we simply use the built-in command line unconditionally &
@@ -315,6 +318,11 @@ static void __init bootcmdline_init(char **cmdline_p)
 		goto out;
 	}
 
+	/* Initialize seq_buf pointing to boot_command_line */
+	s.buffer = boot_command_line;
+	s.size = COMMAND_LINE_SIZE;
+	s.len = strlen(boot_command_line);
+
 #ifdef CONFIG_OF_FLATTREE
 	/*
 	 * If CONFIG_CMDLINE_BOOTLOADER is enabled and we are in FDT-based system,
@@ -323,11 +331,11 @@ static void __init bootcmdline_init(char **cmdline_p)
 	 * to boot_command_line.
 	 */
 	if (initial_boot_params) {
-		if (boot_command_line[0])
-			strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
+		if (s.len)
+			seq_buf_puts(&s, " ");
 
-		if (!strstr(boot_command_line, init_command_line))
-			strlcat(boot_command_line, init_command_line, COMMAND_LINE_SIZE);
+		if (!strstr(s.buffer, init_command_line))
+			seq_buf_puts(&s, init_command_line);
 
 		goto out;
 	}
@@ -338,14 +346,14 @@ static void __init bootcmdline_init(char **cmdline_p)
 	 * CONFIG_CMDLINE_EXTEND is enabled.
 	 */
 	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && CONFIG_CMDLINE[0]) {
-		strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
-		strlcat(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
+		seq_buf_puts(&s, " ");
+		seq_buf_puts(&s, CONFIG_CMDLINE);
 	}
 
 	/*
 	 * Use built-in command line if the bootloader command line is empty.
 	 */
-	if (IS_ENABLED(CONFIG_CMDLINE_BOOTLOADER) && !boot_command_line[0])
+	if (IS_ENABLED(CONFIG_CMDLINE_BOOTLOADER) && !s.len)
 		strscpy(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
 
 out:
-- 
2.55.0.1032.g73a4cd73de-goog