Subject: [PATCH 17/17] arm64: Move "nokaslr" over to the early cpufeature infrastructure

From: Marc Zyngier <[email-masked]>
Date: Mon, 28 Dec 2020 10:49:58 +0000

Given that the early cpufeature infrastructure has borrowed quite
a lot of code from the kaslr implementation, let's reimplement
the matching of the "nokaslr" option with it.

Signed-off-by: Marc Zyngier <[email-masked]>
---
 arch/arm64/kernel/idreg-override.c | 15 ++++++++++++
 arch/arm64/kernel/kaslr.c          | 37 +++---------------------------
 2 files changed, 18 insertions(+), 34 deletions(-)

diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 5296cd77895b..e1cab885d98a 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -33,8 +33,22 @@ static const struct reg_desc mmfr1 __initdata = {
 	},
 };
 
+extern u64 kaslr_feature_val;
+extern u64 kaslr_feature_mask;
+
+static const struct reg_desc kaslr __initdata = {
+	.name		= "kaslr",
+	.val		= &kaslr_feature_val,
+	.mask		= &kaslr_feature_mask,
+	.fields		= {
+		{ "disabled", 0 },
+		{}
+	},
+};
+
 static const struct reg_desc * const regs[] __initdata = {
 	&mmfr1,
+	&kaslr,
 };
 
 static const struct {
@@ -43,6 +57,7 @@ static const struct {
 } aliases[] __initdata = {
 	{ "kvm-arm.mode=nvhe",		"id_aa64mmfr1.vh=0" },
 	{ "kvm-arm.mode=protected",	"id_aa64mmfr1.vh=0" },
+	{ "nokaslr",			"kaslr.disabled=1" },
 };
 
 static int __init find_field(const char *cmdline, const struct reg_desc *reg,
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index 5fc86e7d01a1..dcc4a5aadbe2 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -51,39 +51,8 @@ static __init u64 get_kaslr_seed(void *fdt)
 	return ret;
 }
 
-static __init bool cmdline_contains_nokaslr(const u8 *cmdline)
-{
-	const u8 *str;
-
-	str = strstr(cmdline, "nokaslr");
-	return str == cmdline || (str > cmdline && *(str - 1) == ' ');
-}
-
-static __init bool 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);
-}
+u64 kaslr_feature_val __initdata;
+u64 kaslr_feature_mask __initdata;
 
 /*
  * This routine will be executed with the kernel mapped at its default virtual
@@ -126,7 +95,7 @@ u64 __init kaslr_early_init(void)
 	 * Check if 'nokaslr' appears on the command line, and
 	 * return 0 if that is the case.
 	 */
-	if (is_kaslr_disabled_cmdline(fdt)) {
+	if (kaslr_feature_val & kaslr_feature_mask & 0xf) {
 		kaslr_status = KASLR_DISABLED_CMDLINE;
 		return 0;
 	}
-- 
2.29.2

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