From: Andre Przywara <andre.przywara@arm.com>
To: Mark Rutland <mark.rutland@arm.com>,
linux-arm-kernel@lists.infradead.org
Cc: alexandru.elisei@arm.com, maz@kernel.org
Subject: Re: [boot-wrapper PATCH 2/5] aarch32: simplify _switch_monitor
Date: Tue, 24 Aug 2021 17:50:23 +0100 [thread overview]
Message-ID: <cb6dcb78-a5d6-f1e9-7c49-c1d194e8e568@arm.com> (raw)
In-Reply-To: <20210824134900.34849-3-mark.rutland@arm.com>
On 8/24/21 2:48 PM, Mark Rutland wrote:
> If we're lucky enough to have been booted into secure PL1, we can switch
> to monitor mode with an exception return rather than an SMC call, which
> avoids the need for boot-time vectors.
>
> Note that while all Secure PL1 register state is accessible in Secure
> SVC mode, we must switch to Monitor mode before we set SCR.NS=1.
>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
I don't know much about the subtle differences between smc, movs pc and
eret, but from what I read this is indeed an easier way to get to MON.
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Cheers,
Andre
> ---
> arch/aarch32/boot.S | 19 ++++---------------
> 1 file changed, 4 insertions(+), 15 deletions(-)
>
> diff --git a/arch/aarch32/boot.S b/arch/aarch32/boot.S
> index 82927de..e397cb0 100644
> --- a/arch/aarch32/boot.S
> +++ b/arch/aarch32/boot.S
> @@ -37,9 +37,10 @@ ASM_FUNC(_start)
> b start_no_el3
>
> _switch_monitor:
> - ldr r0, =boot_vectors
> - bl setup_vector
> - smc #0
> + adr lr, _monitor
> + ldr r0, =(PSR_A | PSR_I | PSR_F | PSR_MON)
> + msr spsr, r0
> + movs pc, lr
>
> _monitor:
> /* Move the stack to Monitor mode*/
> @@ -102,18 +103,6 @@ ASM_FUNC(jump_kernel)
> msr spsr_cxf, r4
> movs pc, lr
>
> - .section .vectors
> - .align 6
> -boot_vectors:
> - b .
> - b .
> - b _monitor
> - b .
> - b .
> - b .
> - b .
> - b .
> -
> .section .data
> .align 2
> flag_no_el3:
>
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next prev parent reply other threads:[~2021-08-24 16:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-24 13:48 [boot-wrapper PATCH 0/5] Misc cleanups Mark Rutland
2021-08-24 13:48 ` [boot-wrapper PATCH 1/5] Remove unused Set/Way cache helpers Mark Rutland
2021-08-24 16:49 ` Andre Przywara
2021-08-24 13:48 ` [boot-wrapper PATCH 2/5] aarch32: simplify _switch_monitor Mark Rutland
2021-08-24 16:50 ` Andre Przywara [this message]
2021-08-24 13:48 ` [boot-wrapper PATCH 3/5] GICv3: initialize without RMW Mark Rutland
2021-08-24 16:50 ` Andre Przywara
2021-08-24 13:48 ` [boot-wrapper PATCH 4/5] Rename kernel *_RESET values to *_KERNEL Mark Rutland
2021-08-24 16:50 ` Andre Przywara
2021-08-24 13:49 ` [boot-wrapper PATCH 5/5] Rename `CNTFRQ` -> `COUNTER_FREQ` Mark Rutland
2021-08-24 16:51 ` Andre Przywara
2021-08-25 9:46 ` [boot-wrapper PATCH 0/5] Misc cleanups Marc Zyngier
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