arm64: Add support for read and write registers at current EL in assembly

In order to ease the process of reading and writing any register at current EL,
provide read_current and write_current assembly macros. These are included in
arch/lib_helpers.h under the __ASSEMBLY__ macro condition. This is done to allow
the same header file to be included by .c and .S files.

BUG=chrome-os-partner:30785
BRANCH=None
TEST=Compiles successfully

Change-Id: I51749b6e4ae7b1ffbaae28d915cd100a28959f26
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: c11c7287f507fa398cbbee75abc2bd11140ef19b
Original-Change-Id: I1258850438624abfe3b1ed7240df0db0e7905be6
Original-Signed-off-by: Furquan Shaikh <furquan@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/216373
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-by: Tom Warren <twarren@nvidia.com>
Original-Tested-by: Furquan Shaikh <furquan@chromium.org>
Original-Commit-Queue: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/9062
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

1 files changed, 97 insertions, 0 deletions

diff --git a/src/arch/arm64/include/armv8/arch/lib_helpers.h b/src/arch/arm64/include/armv8/arch/lib_helpers.h
index 57b63d8684..958b8e7206 100644
--- a/src/arch/arm64/include/armv8/arch/lib_helpers.h
+++ b/src/arch/arm64/include/armv8/arch/lib_helpers.h
@@ -22,6 +22,9 @@
  * file.
  */
 
+#ifndef __ARCH_LIB_HELPERS_H__
+#define __ARCH_LIB_HELPERS_H__
+
 #define EL0               0
 #define EL1               1
 #define EL2               2
@@ -30,6 +33,96 @@
 #define CURRENT_EL_MASK   0x3
 #define CURRENT_EL_SHIFT  2
 
+#ifdef __ASSEMBLY__
+
+/* Macro to switch to label based on current el */
+.macro switch_el xreg label1 label2 label3
+	mrs	\xreg, CurrentEL
+	/* Currently at EL1 */
+	 cmp	\xreg, #(EL1 << CURRENT_EL_SHIFT)
+	b.eq	\label1
+	/* Currently at EL2 */
+	cmp	\xreg, #(EL2 << CURRENT_EL_SHIFT)
+	b.eq	\label2
+	/* Currently at EL3 */
+	cmp	\xreg, #(EL3 << CURRENT_EL_SHIFT)
+	b.eq	\label3
+.endm
+
+/* Macro to read sysreg at current EL
+   xreg - reg in which read value needs to be stored
+   sysreg - system reg that is to be read
+*/
+.macro read_current xreg sysreg
+	switch_el \xreg, 101f, 102f, 103f
+101:
+	mrs	\xreg, \sysreg\()_el1
+	b	104f
+102:
+	mrs	\xreg, \sysreg\()_el2
+	b	104f
+103:
+	mrs	\xreg, \sysreg\()_el3
+	b	104f
+104:
+.endm
+
+/* Macro to write sysreg at current EL
+   xreg - reg from which value needs to be written
+   sysreg - system reg that is to be written
+   temp - temp reg that can be used to read current EL
+*/
+.macro write_current sysreg xreg temp
+	switch_el \temp, 101f, 102f, 103f
+101:
+	msr	\sysreg\()_el1, \xreg
+	b	104f
+102:
+	msr	\sysreg\()_el2, \xreg
+	b	104f
+103:
+	msr	\sysreg\()_el3, \xreg
+	b	104f
+104:
+.endm
+
+/* Macro to read sysreg at current EL - 1
+   xreg - reg in which read value needs to be stored
+   sysreg - system reg that is to be read
+*/
+.macro read_lower xreg sysreg
+	switch_el \xreg, 101f, 102f, 103f
+101:
+	b	104f
+102:
+	mrs	\xreg, \sysreg\()_el1
+	b	104f
+103:
+	mrs	\xreg, \sysreg\()_el2
+	b	104f
+104:
+.endm
+
+/* Macro to write sysreg at current EL - 1
+   xreg - reg from which value needs to be written
+   sysreg - system reg that is to be written
+   temp - temp reg that can be used to read current EL
+*/
+.macro write_lower sysreg xreg temp
+	switch_el \temp, 101f, 102f, 103f
+101:
+	b	104f
+102:
+	msr	\sysreg\()_el1, \xreg
+	b	104f
+103:
+	msr	\sysreg\()_el2, \xreg
+	b	104f
+104:
+.endm
+
+#else
+
 #define DAIF_DBG_BIT      (1<<3)
 #define DAIF_ABT_BIT      (1<<2)
 #define DAIF_IRQ_BIT      (1<<1)
@@ -290,3 +383,7 @@ void tlbiallis_el2(void);
 void tlbiallis_el3(void);
 void tlbiallis_current(void);
 void tlbivaa_el1(uint64_t va);
+
+#endif // __ASSEMBLY__
+
+#endif // __ARCH_LIB_HELPERS_H__