AArch64: Refactor GP register restore to separate function
At present, the function that restores general purpose registers also
does ERET. Refactor the restore code to restore general purpose
registers without ERET to complement the save function.
The macro save_x18_to_x29_sp_el0 was used only once, and is therefore
removed, and its contents expanded inline for readability.
No functional changes, but with this patch:
- The SMC return path will incur an branch-return and an additional
register load.
- The unknown SMC path restores registers x0 to x3.
Change-Id: I7a1a63e17f34f9cde810685d70a0ad13ca3b7c50
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
diff --git a/lib/el3_runtime/aarch64/context.S b/lib/el3_runtime/aarch64/context.S
index 620ec16..9a53b76 100644
--- a/lib/el3_runtime/aarch64/context.S
+++ b/lib/el3_runtime/aarch64/context.S
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2013-2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2018, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
@@ -15,8 +15,8 @@
.global fpregs_context_restore
#endif
.global save_gp_registers
+ .global restore_gp_registers
.global restore_gp_registers_eret
- .global restore_gp_registers_callee_eret
.global el3_exit
/* -----------------------------------------------------
@@ -332,30 +332,40 @@
ret
endfunc save_gp_registers
-func restore_gp_registers_eret
+/*
+ * This function restores all general purpose registers except x30 from the
+ * CPU context. x30 register must be explicitly restored by the caller.
+ */
+func restore_gp_registers
ldp x0, x1, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X0]
ldp x2, x3, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X2]
- b restore_gp_registers_callee_eret
-endfunc restore_gp_registers_eret
-
-func restore_gp_registers_callee_eret
ldp x4, x5, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X4]
ldp x6, x7, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X6]
ldp x8, x9, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X8]
ldp x10, x11, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X10]
ldp x12, x13, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X12]
ldp x14, x15, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X14]
+ ldp x16, x17, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X16]
ldp x18, x19, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X18]
ldp x20, x21, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X20]
ldp x22, x23, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X22]
ldp x24, x25, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X24]
ldp x26, x27, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X26]
+ ldr x28, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_SP_EL0]
+ msr sp_el0, x28
ldp x28, x29, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X28]
- ldp x30, x17, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
- msr sp_el0, x17
- ldp x16, x17, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X16]
+ ret
+endfunc restore_gp_registers
+
+/*
+ * Restore general purpose registers (including x30), and exit EL3 via. ERET to
+ * a lower exception level.
+ */
+func restore_gp_registers_eret
+ bl restore_gp_registers
+ ldr x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
eret
-endfunc restore_gp_registers_callee_eret
+endfunc restore_gp_registers_eret
/* -----------------------------------------------------
* This routine assumes that the SP_EL3 is pointing to