refactor(el3_runtime): introduce save_x30 macro

Most of the macros/routine in vector entry need a free scratch register.
Introduce a macro "save_x30" and call it right at the begining of vector
entries where x30 is used. It is more exlicit and less error prone

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I617f3d41a120739e5e3fe1c421c79ceb70c1188e

bl31/aarch64/runtime_exceptions.S

@@ -39,6 +39,14 @@
 	.globl	fiq_aarch32
 	.globl	serror_aarch32
 
+	/*
+	 * Save LR and make x30 available as most of the routines in vector entry
+	 * need a free register
+	 */
+	.macro save_x30
+	str	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
+	.endm
+
 	/*
 	 * Macro that prepares entry to EL3 upon taking an exception.
 	 *
@@ -58,12 +66,6 @@
 	/* Unmask the SError interrupt */
 	msr	daifclr, #DAIF_ABT_BIT
 
-	/*
-	 * Explicitly save x30 so as to free up a register and to enable
-	 * branching
-	 */
-	str	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
-
 	/* Check for SErrors synchronized by the ESB instruction */
 	mrs	x30, DISR_EL1
 	tbz	x30, #DISR_A_BIT, 1f
@@ -108,11 +110,7 @@
 	/* Use ISB for the above unmask operation to take effect immediately */
 	isb
 
-	/*
-	 * Refer Note 1.
-	 * No need to restore X30 as macros following this modify x30 anyway.
-	 */
-	str	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
+	/* Refer Note 1. */
 	mov 	x30, #1
 	str	x30, [sp, #CTX_EL3STATE_OFFSET + CTX_IS_IN_EL3]
 	dmb	sy
@@ -316,7 +314,7 @@ vector_entry serror_sp_elx
 	 * triggered due to explicit synchronization in EL3. Refer Note 1.
 	 */
 	/* Assumes SP_EL3 on entry */
-	str	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
+	save_x30
 	ldr	x30, [sp, #CTX_EL3STATE_OFFSET + CTX_IS_IN_EL3]
 	cbnz	x30, 1f
 
@@ -338,24 +336,28 @@ vector_entry sync_exception_aarch64
 	 * to a valid cpu context where the general purpose and system register
 	 * state can be saved.
 	 */
+	save_x30
 	apply_at_speculative_wa
 	check_and_unmask_ea
 	handle_sync_exception
 end_vector_entry sync_exception_aarch64
 
 vector_entry irq_aarch64
+	save_x30
 	apply_at_speculative_wa
 	check_and_unmask_ea
 	handle_interrupt_exception irq_aarch64
 end_vector_entry irq_aarch64
 
 vector_entry fiq_aarch64
+	save_x30
 	apply_at_speculative_wa
 	check_and_unmask_ea
 	handle_interrupt_exception fiq_aarch64
 end_vector_entry fiq_aarch64
 
 vector_entry serror_aarch64
+	save_x30
 	apply_at_speculative_wa
 #if RAS_EXTENSION
 	msr	daifclr, #DAIF_ABT_BIT
@@ -377,24 +379,28 @@ vector_entry sync_exception_aarch32
 	 * to a valid cpu context where the general purpose and system register
 	 * state can be saved.
 	 */
+	save_x30
 	apply_at_speculative_wa
 	check_and_unmask_ea
 	handle_sync_exception
 end_vector_entry sync_exception_aarch32
 
 vector_entry irq_aarch32
+	save_x30
 	apply_at_speculative_wa
 	check_and_unmask_ea
 	handle_interrupt_exception irq_aarch32
 end_vector_entry irq_aarch32
 
 vector_entry fiq_aarch32
+	save_x30
 	apply_at_speculative_wa
 	check_and_unmask_ea
 	handle_interrupt_exception fiq_aarch32
 end_vector_entry fiq_aarch32
 
 vector_entry serror_aarch32
+	save_x30
 	apply_at_speculative_wa
 #if RAS_EXTENSION
 	msr	daifclr, #DAIF_ABT_BIT

include/arch/aarch64/el2_common_macros.S

@@ -384,13 +384,12 @@
 	.macro	apply_at_speculative_wa
 #if ERRATA_SPECULATIVE_AT
 	/*
-	 * Explicitly save x30 so as to free up a register and to enable
-	 * branching and also, save x29 which will be used in the called
-	 * function
+	 * This function expects x30 has been saved.
+	 * Also, save x29 which will be used in the called function.
 	 */
-	stp	x29, x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X29]
+	str	x29, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X29]
 	bl	save_and_update_ptw_el1_sys_regs
-	ldp	x29, x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X29]
+	ldr	x29, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X29]
 #endif
 	.endm
 

include/arch/aarch64/el3_common_macros.S

@@ -532,13 +532,12 @@
 	.macro	apply_at_speculative_wa
 #if ERRATA_SPECULATIVE_AT
 	/*
-	 * Explicitly save x30 so as to free up a register and to enable
-	 * branching and also, save x29 which will be used in the called
-	 * function
+	 * This function expects x30 has been saved.
+	 * Also, save x29 which will be used in the called function.
 	 */
-	stp	x29, x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X29]
+	str	x29, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X29]
 	bl	save_and_update_ptw_el1_sys_regs
-	ldp	x29, x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X29]
+	ldr	x29, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X29]
 #endif
 	.endm