arm64: record boot mode when entering the kernel

To be able to signal the availability of EL2 to other parts of
the kernel, record the boot mode.

Once booted, two predicates indicate if HYP mode is available,
and if not, whether this is due to a boot mode mismatch or not.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
new file mode 100644
index 000000000000..f28547d9edfa
--- /dev/null
+++ b/arch/arm64/include/asm/virt.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __ASM__VIRT_H
+#define __ASM__VIRT_H
+
+#define BOOT_CPU_MODE_EL2       (0x0e12b007)
+
+#ifndef __ASSEMBLY__
+
+/*
+ * __boot_cpu_mode records what mode CPUs were booted in.
+ * A correctly-implemented bootloader must start all CPUs in the same mode:
+ * In this case, both 32bit halves of __boot_cpu_mode will contain the
+ * same value (either 0 if booted in EL1, BOOT_CPU_MODE_EL2 if booted in EL2).
+ *
+ * Should the bootloader fail to do this, the two values will be different.
+ * This allows the kernel to flag an error when the secondaries have come up.
+ */
+extern u32 __boot_cpu_mode[2];
+
+/* Reports the availability of HYP mode */
+static inline bool is_hyp_mode_available(void)
+{
+        return (__boot_cpu_mode[0] == BOOT_CPU_MODE_EL2 &&
+                __boot_cpu_mode[1] == BOOT_CPU_MODE_EL2);
+}
+
+/* Check if the bootloader has booted CPUs in different modes */
+static inline bool is_hyp_mode_mismatched(void)
+{
+        return __boot_cpu_mode[0] != __boot_cpu_mode[1];
+}
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* ! __ASM__VIRT_H */