From 060260a6be47ae163b0c71a6d0902d065b68f3d2 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Wed, 29 Nov 2023 12:16:14 +0100 Subject: arm64: idreg-override: Avoid sprintf() for simple string concatenation 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 Link: https://lore.kernel.org/r/20231129111555.3594833-61-ardb@google.com Signed-off-by: Will Deacon --- arch/arm64/kernel/idreg-override.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) (limited to 'arch/arm64/kernel/idreg-override.c') diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c index 8b22ca523186..cf1df5f6fbc1 100644 --- a/arch/arm64/kernel/idreg-override.c +++ b/arch/arm64/kernel/idreg-override.c @@ -206,14 +206,15 @@ static int __init parse_nokaslr(char *unused) } early_param("nokaslr", parse_nokaslr); -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 '=' to obtain '.=' + memcpy(opt + len, reg->fields[f].name, flen); + len += flen; + opt[len++] = '='; if (memcmp(cmdline, opt, len)) return -1; @@ -223,15 +224,21 @@ 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_pointer(regs[i].reg); struct arm64_ftr_override *override; + int len = strlen(reg->name); int f; override = prel64_pointer(reg->override); + // set opt[] to '.' + 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; @@ -239,7 +246,7 @@ 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; /* -- cgit v1.2.3