[PATCH v4 18/21] arm64: Move "nokaslr" over to the early cpufeature infrastructure

[Marc Zyngier]

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 <m...@kernel.org>
---
 arch/arm64/kernel/idreg-override.c | 17 ++++++++++++++
 arch/arm64/kernel/kaslr.c          | 37 +++---------------------------
 2 files changed, 20 insertions(+), 34 deletions(-)

diff --git a/arch/arm64/kernel/idreg-override.c 
b/arch/arm64/kernel/idreg-override.c
index 1db54878b2c4..143fe7b8e3ce 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -33,8 +33,24 @@ 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",
+#ifdef CONFIG_RANDOMIZE_BASE
+       .val            = &kaslr_feature_val,
+       .mask           = &kaslr_feature_mask,
+#endif
+       .fields         = {
+               { "disabled", 0 },
+               {}
+       },
+};
+
 static const struct reg_desc * const regs[] __initdata = {
        &mmfr1,
+       &kaslr,
 };
 
 static const struct {
@@ -43,6 +59,7 @@ 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