[PATCH v5 26/39] arm64: kaslr: Use feature override instead of parsing the cmdline again

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb at kernel.org>

The early kaslr code open codes the detection of 'nokaslr' on the kernel
command line, and this is no longer necessary now that the feature
detection code, which also looks for the same string, executes before
this code.

Note that the pseudo-feature's mask can be disregarded: it is used for
true CPU features to mask the CPU feature register, not the value of the
override.

Signed-off-by: Ard Biesheuvel <ardb at kernel.org>
---
 arch/arm64/include/asm/cpufeature.h |  8 +++
 arch/arm64/kernel/kaslr.c           |  4 +-
 arch/arm64/kernel/pi/kaslr_early.c  | 53 +-------------------
 3 files changed, 10 insertions(+), 55 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index f6d416fe49b0..77ed3b28cbc6 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -909,6 +909,14 @@ extern struct arm64_ftr_override id_aa64isar2_override;
 
 extern struct arm64_ftr_override arm64_sw_feature_override;
 
+static inline bool kaslr_disabled_cmdline(void)
+{
+	if (cpuid_feature_extract_unsigned_field(arm64_sw_feature_override.val,
+						 ARM64_SW_FEATURE_OVERRIDE_NOKASLR))
+		return true;
+	return false;
+}
+
 u32 get_kvm_ipa_limit(void);
 void dump_cpu_features(void);
 
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index 94a269cd1f07..efbeb8356769 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -16,9 +16,7 @@ bool __ro_after_init __kaslr_is_enabled = false;
 
 void __init kaslr_init(void)
 {
-	if (cpuid_feature_extract_unsigned_field(arm64_sw_feature_override.val &
-						 arm64_sw_feature_override.mask,
-						 ARM64_SW_FEATURE_OVERRIDE_NOKASLR)) {
+	if (kaslr_disabled_cmdline()) {
 		pr_info("KASLR disabled on command line\n");
 		return;
 	}
diff --git a/arch/arm64/kernel/pi/kaslr_early.c b/arch/arm64/kernel/pi/kaslr_early.c
index 167081b30a15..f2305e276ec3 100644
--- a/arch/arm64/kernel/pi/kaslr_early.c
+++ b/arch/arm64/kernel/pi/kaslr_early.c
@@ -16,57 +16,6 @@
 #include <asm/memory.h>
 #include <asm/pgtable.h>
 
-/* taken from lib/string.c */
-static char *__init __strstr(const char *s1, const char *s2)
-{
-	size_t l1, l2;
-
-	l2 = strlen(s2);
-	if (!l2)
-		return (char *)s1;
-	l1 = strlen(s1);
-	while (l1 >= l2) {
-		l1--;
-		if (!memcmp(s1, s2, l2))
-			return (char *)s1;
-		s1++;
-	}
-	return NULL;
-}
-static bool __init cmdline_contains_nokaslr(const u8 *cmdline)
-{
-	const u8 *str;
-
-	str = __strstr(cmdline, "nokaslr");
-	return str == cmdline || (str > cmdline && *(str - 1) == ' ');
-}
-
-static bool __init is_kaslr_disabled_cmdline(void *fdt)
-{
-	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
-		int node;
-		const u8 *prop;
-
-		node = fdt_path_offset(fdt, "/chosen");
-		if (node < 0)
-			goto out;
-
-		prop = fdt_getprop(fdt, node, "bootargs", NULL);
-		if (!prop)
-			goto out;
-
-		if (cmdline_contains_nokaslr(prop))
-			return true;
-
-		if (IS_ENABLED(CONFIG_CMDLINE_EXTEND))
-			goto out;
-
-		return false;
-	}
-out:
-	return cmdline_contains_nokaslr(CONFIG_CMDLINE);
-}
-
 static u64 __init get_kaslr_seed(void *fdt)
 {
 	static char const chosen_str[] __initconst = "chosen";
@@ -92,7 +41,7 @@ asmlinkage u64 __init kaslr_early_init(void *fdt)
 {
 	u64 seed, range;
 
-	if (is_kaslr_disabled_cmdline(fdt))
+	if (kaslr_disabled_cmdline())
 		return 0;
 
 	seed = get_kaslr_seed(fdt);
-- 
2.43.0.rc1.413.gea7ed67945-goog