Commit 23c8a500 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Will Deacon
Browse files

arm64: kernel: use ordinary return/argument register for el2_setup() 



The function el2_setup() passes its return value in register w20, and
in the two cases where the caller actually cares about this return value,
it is passed into set_cpu_boot_mode_flag() [almost] directly, which
expects its input in w20 as well.

So there is no reason to use a 'special' callee saved register here, but
we can simply follow the PCS for return value and first argument,
respectively.

Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent b5fe2429

arch/arm64/kernel/head.S

+7 −7
Original line number Diff line number Diff line
@@ -210,7 +210,7 @@ efi_header_end: 


ENTRY(stext)

	bl	preserve_boot_args

	bl	el2_setup			// Drop to EL1, w20=cpu_boot_mode

	bl	el2_setup			// Drop to EL1, w0=cpu_boot_mode

	adrp	x24, __PHYS_OFFSET

	and	x23, x24, MIN_KIMG_ALIGN - 1	// KASLR offset, defaults to 0

	bl	set_cpu_boot_mode_flag
@@ -488,7 +488,7 @@ CPU_LE( bic x0, x0, #(1 << 25) ) // Clear the EE bit for EL2 
CPU_BE(	orr	x0, x0, #(3 << 24)	)	// Set the EE and E0E bits for EL1

CPU_LE(	bic	x0, x0, #(3 << 24)	)	// Clear the EE and E0E bits for EL1

	msr	sctlr_el1, x0

	mov	w20, #BOOT_CPU_MODE_EL1		// This cpu booted in EL1

	mov	w0, #BOOT_CPU_MODE_EL1		// This cpu booted in EL1

	isb

	ret
@@ -584,7 +584,7 @@ CPU_LE( movk x0, #0x30d0, lsl #16 ) // Clear EE and E0E on LE systems 


	cbz	x2, install_el2_stub



	mov	w20, #BOOT_CPU_MODE_EL2		// This CPU booted in EL2

	mov	w0, #BOOT_CPU_MODE_EL2		// This CPU booted in EL2

	isb

	ret
@@ -599,7 +599,7 @@ install_el2_stub: 
		      PSR_MODE_EL1h)

	msr	spsr_el2, x0

	msr	elr_el2, lr

	mov	w20, #BOOT_CPU_MODE_EL2		// This CPU booted in EL2

	mov	w0, #BOOT_CPU_MODE_EL2		// This CPU booted in EL2

	eret

ENDPROC(el2_setup)
@@ -609,10 +609,10 @@ ENDPROC(el2_setup) 
 */

set_cpu_boot_mode_flag:

	adr_l	x1, __boot_cpu_mode

	cmp	w20, #BOOT_CPU_MODE_EL2

	cmp	w0, #BOOT_CPU_MODE_EL2

	b.ne	1f

	add	x1, x1, #4

1:	str	w20, [x1]			// This CPU has booted in EL1

1:	str	w0, [x1]			// This CPU has booted in EL1

	dmb	sy

	dc	ivac, x1			// Invalidate potentially stale cache line

	ret
@@ -649,7 +649,7 @@ ENTRY(__early_cpu_boot_status) 
	 * cores are held until we're ready for them to initialise.

	 */

ENTRY(secondary_holding_pen)

	bl	el2_setup			// Drop to EL1, w20=cpu_boot_mode

	bl	el2_setup			// Drop to EL1, w0=cpu_boot_mode

	bl	set_cpu_boot_mode_flag

	mrs	x0, mpidr_el1

	mov_q	x1, MPIDR_HWID_BITMASK

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