Re: [boot-wrapper PATCH 04/12] Remove `flag_no_el3`

We set `flag_no_el3` when not booted at EL3 / monitor mode, and
subsequently we use this to determine whether we need to drop exception
level before entering Linux. As this can be derived from CurrentEL or
CPSR, the flag itself is redundant, and we can defer the check until
we're about to enter Linux.

In future this will allow more logic to be converted into C, where it
will be easier to handle architectural variants.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
---
 arch/aarch32/boot.S | 14 +++-----------
 arch/aarch64/boot.S | 13 ++-----------
 2 files changed, 5 insertions(+), 22 deletions(-)

diff --git a/arch/aarch32/boot.S b/arch/aarch32/boot.S
index 2a85ad5..0bd1ca2 100644
--- a/arch/aarch32/boot.S
+++ b/arch/aarch32/boot.S

@@ -31,9 +31,6 @@ ENTRY(_start)
 	cmp	r0, #PSR_HYP
 	bne	_switch_monitor

 
-	mov	r0, #1
-	ldr	r1, =flag_no_el3
-	str	r0, [r1]
 	b	start_no_el3
 
 _switch_monitor:

@@ -89,9 +86,9 @@ ENTRY(jump_kernel)
 	ldr	lr, [r5], #4
 	ldm	r5, {r0 - r2}
 
-	ldr	r4, =flag_no_el3
-	ldr	r4, [r4]
-	cmp	r4, #1
+	mrs	r4, cpsr
+	and	r4, #PSR_MODE_MASK
+	cmp	r4, #PSR_MON

 	bxeq	lr				@ no EL3
 
 	ldr	r4, =SPSR_KERNEL

@@ -113,8 +110,3 @@ boot_vectors:
 	b	.
 	b	.
 	b	.
-
-	.section .data
-	.align 2
-flag_no_el3:
-	.long 0

diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
index 37759ce..fae0188 100644
--- a/arch/aarch64/boot.S
+++ b/arch/aarch64/boot.S

@@ -28,10 +28,6 @@ _start:
 	cmp	x0, #CURRENTEL_EL3
 	b.eq	1f

 
-	mov	w0, #1
-	ldr	x1, =flag_no_el3
-	str	w0, [x1]
-
 	b	start_no_el3
 
 1:	mov	x0, #0x30			// RES1

@@ -140,8 +136,8 @@ jump_kernel:
 	bl	find_logical_id
 	bl	setup_stack		// Reset stack pointer
 
-	ldr	w0, flag_no_el3
-	cmp	w0, #0			// Prepare Z flag
+	mrs	x0, CurrentEl
+	cmp	w0, #CURRENTEL_EL3	// Prepare Z flag
 
 	mov	x0, x20
 	mov	x1, x21

@@ -164,8 +160,3 @@ jump_kernel:
 	eret
 
 	.ltorg
-
-	.data
-	.align 3
-flag_no_el3:
-	.long 0