diff mbox series

[v3,21/60] arm64: idreg-override: Avoid sprintf() for simple string concatenation

Message ID 20230307140522.2311461-22-ardb@kernel.org
State New
Headers
Series arm64: Add support for LPA2 at stage1 and WXN |

Commit Message

Ard Biesheuvel March 7, 2023, 2:04 p.m. UTC 
  Instead of using sprintf() with the "%s.%s=" format, where the first
string argument is always the same in the inner loop of match_options(),
use simple memcpy() for string concatenation, and move the first copy to
the outer loop. This removes the dependency on sprintf(), which will be
difficult to fulfil when we move this code into the early mini C
runtime.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/kernel/idreg-override.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 476dc3f0e9d90e22..58c02fe20e1050b4 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -195,14 +195,15 @@  static const struct {
 	{ "nokaslr",			"arm64_sw.nokaslr=1" },
 };
 
-static int __init find_field(const char *cmdline,
+static int __init find_field(const char *cmdline, char *opt, int len,
 			     const struct ftr_set_desc *reg, int f, u64 *v)
 {
-	char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
-	int len;
+	int flen = strlen(reg->fields[f].name);
 
-	len = snprintf(opt, ARRAY_SIZE(opt), "%s.%s=",
-		       reg->name, reg->fields[f].name);
+	// append '<fieldname>=' to obtain '<name>.<fieldname>='
+	memcpy(opt + len, reg->fields[f].name, flen);
+	len += flen;
+	opt[len++] = '=';
 
 	if (memcmp(cmdline, opt, len))
 		return -1;
@@ -212,15 +213,21 @@  static int __init find_field(const char *cmdline,
 
 static void __init match_options(const char *cmdline)
 {
+	char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(regs); i++) {
 		const struct ftr_set_desc *reg = prel64_to_pointer(&regs[i].reg_prel);
 		struct arm64_ftr_override *override;
+		int len = strlen(reg->name);
 		int f;
 
 		override = prel64_to_pointer(&reg->override_prel);
 
+		// set opt[] to '<name>.'
+		memcpy(opt, reg->name, len);
+		opt[len++] = '.';
+
 		for (f = 0; reg->fields[f].name[0] != '\0'; f++) {
 			u64 shift = reg->fields[f].shift;
 			u64 width = reg->fields[f].width ?: 4;
@@ -228,7 +235,7 @@  static void __init match_options(const char *cmdline)
 			bool (*filter)(u64 val);
 			u64 v;
 
-			if (find_field(cmdline, reg, f, &v))
+			if (find_field(cmdline, opt, len, reg, f, &v))
 				continue;
 
 			/*