In order to be able to override CPU features at boot time,
let's add a command line parser that matches options of the
form "cpureg.feature=value", and store the corresponding
value into the override val/mask pair.
No features are currently defined, so no expected change in
functionality.
Signed-off-by: Marc Zyngier
Acked-by: David Brazdil
---
arch/arm64/kernel/Makefile | 2 +-
arch/arm64/kernel/head.S | 1 +
arch/arm64/kernel/idreg-override.c | 130 +
3 files changed, 132 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/kernel/idreg-override.c
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 86364ab6f13f..2262f0392857 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -17,7 +17,7 @@ obj-y := debug-monitors.o entry.o irq.o
fpsimd.o \
return_address.o cpuinfo.o cpu_errata.o
\
cpufeature.o alternative.o cacheinfo.o
\
smp.o smp_spin_table.o topology.o smccc-call.o
\
- syscall.o proton-pack.o
+ syscall.o proton-pack.o idreg-override.o
targets+= efi-entry.o
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index d74e5f84042e..3243e3ae9bd8 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -435,6 +435,7 @@ SYM_FUNC_START_LOCAL(__primary_switched)
mov x0, x21 // pass FDT address in x0
bl early_fdt_map // Try mapping the FDT early
+ bl init_feature_override
bl switch_to_vhe
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
bl kasan_early_init
diff --git a/arch/arm64/kernel/idreg-override.c
b/arch/arm64/kernel/idreg-override.c
new file mode 100644
index ..2d184d6674fd
--- /dev/null
+++ b/arch/arm64/kernel/idreg-override.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Early cpufeature override framework
+ *
+ * Copyright (C) 2020 Google LLC
+ * Author: Marc Zyngier
+ */
+
+#include
+#include
+
+#include
+#include
+
+struct ftr_set_desc {
+ const char *name;
+ struct arm64_ftr_override *override;
+ struct {
+ const char *name;
+ u8 shift;
+ } fields[];
+};
+
+static const struct ftr_set_desc * const regs[] __initdata = {
+};
+
+static char *cmdline_contains_option(const char *cmdline, const char *option)
+{
+ char *str = strstr(cmdline, option);
+
+ if ((str == cmdline || (str > cmdline && *(str - 1) == ' ')))
+ return str;
+
+ return NULL;
+}
+
+static int __init find_field(const char *cmdline,
+const struct ftr_set_desc *reg, int f, u64 *v)
+{
+ char buf[256], *str;
+ size_t len;
+
+ snprintf(buf, ARRAY_SIZE(buf), "%s.%s=", reg->name,
reg->fields[f].name);
+
+ str = cmdline_contains_option(cmdline, buf);
+ if (!str)
+ return -1;
+
+ str += strlen(buf);
+ len = strcspn(str, " ");
+ len = min(len, ARRAY_SIZE(buf) - 1);
+ strncpy(buf, str, len);
+ buf[len] = 0;
+
+ return kstrtou64(buf, 0, v);
+}
+
+static void __init match_options(const char *cmdline)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(regs); i++) {
+ int f;
+
+ if (!regs[i]->override)
+ continue;
+
+ for (f = 0; regs[i]->fields[f].name; f++) {
+ u64 v;
+
+ if (find_field(cmdline, regs[i], f, &v))
+ continue;
+
+ regs[i]->override->val |= (v & 0xf) <<
regs[i]->fields[f].shift;
+ regs[i]->override->mask |= 0xfUL <<
regs[i]->fields[f].shift;
+ }
+ }
+}
+
+static __init void parse_cmdline(void)
+{
+ if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
+ const u8 *prop;
+ void *fdt;
+ int node;
+
+ fdt = get_early_fdt_ptr();
+ if (!fdt)
+ goto out;
+
+ node = fdt_path_offset(fdt, "/chosen");
+ if (node < 0)
+ goto out;
+
+ prop = fdt_getprop(fdt, node, "bootargs", NULL);
+ if (!prop)
+ goto out;
+
+ match_options(prop);
+
+ if (!IS_ENABLED(CONFIG_CMDLINE_EXTEND))
+ return;
+ }
+
+out:
+ match_options(CONFIG_CMDLINE);
+}
+
+/* Keep checkers quiet */
+void init_feature_override(void);
+
+asmlinkage void __init init_feature_override(void)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(regs); i++
