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From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Cc: "Rafał Miłecki" <zajec5@gmail.com>,
	"Will Deacon" <will@kernel.org>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Ard Biesheuvel" <ardb@kernel.org>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	bcm-kernel-feedback-list@broadcom.com, kernel-team@android.com
Subject: [PATCH 2/5] arm64: Handle UNDEF in the EL2 stub vectors
Date: Thu, 12 Aug 2021 20:02:10 +0100	[thread overview]
Message-ID: <20210812190213.2601506-3-maz@kernel.org> (raw)
In-Reply-To: <20210812190213.2601506-1-maz@kernel.org>

As we want to handle the silly case where HVC has been disabled
from EL3, augment our ability to handle exception at EL2.

Check for unknown exceptions (usually UNDEF) coming from EL2,
and treat them as a failing HVC call into the stubs. While
this isn't great and obviously doesn't catter for the gigantic
range of possible exceptions, it isn't any worse than what we
have today.

Just don't try and use it for anything else.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kernel/hyp-stub.S | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
index 43d212618834..026a34515b21 100644
--- a/arch/arm64/kernel/hyp-stub.S
+++ b/arch/arm64/kernel/hyp-stub.S
@@ -46,7 +46,16 @@ SYM_CODE_END(__hyp_stub_vectors)
 	.align 11
 
 SYM_CODE_START_LOCAL(elx_sync)
-	cmp	x0, #HVC_SET_VECTORS
+	mrs	x4, spsr_el2
+	and	x4, x4, #PSR_MODE_MASK
+	orr	x4, x4, #1
+	cmp	x4, #PSR_MODE_EL2h
+	b.ne	0f
+	mrs	x4, esr_el2
+	eor	x4, x4, #ESR_ELx_IL
+	cbz	x4, el2_undef
+
+0:	cmp	x0, #HVC_SET_VECTORS
 	b.ne	1f
 	msr	vbar_el2, x1
 	b	9f
@@ -71,6 +80,14 @@ SYM_CODE_START_LOCAL(elx_sync)
 
 9:	mov	x0, xzr
 	eret
+
+el2_undef:
+	// Assumes this was a HVC that went really wrong...
+	mrs	x0, elr_el2
+	add	x0, x0, #4
+	msr	elr_el2, x0
+	mov_q	x0, HVC_STUB_ERR
+	eret
 SYM_CODE_END(elx_sync)
 
 // nVHE? No way! Give me the real thing!
-- 
2.30.2


  parent reply	other threads:[~2021-08-12 19:02 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-12 19:02 [PATCH 0/5] arm64: Survival kit for SCR_EL3.HCE==0 conditions Marc Zyngier
2021-08-12 19:02 ` [PATCH 1/5] arm64: Directly expand __init_el2_nvhe_prepare_eret where needed Marc Zyngier
2021-08-12 19:02 ` Marc Zyngier [this message]
2021-08-13 13:08   ` [PATCH 2/5] arm64: Handle UNDEF in the EL2 stub vectors Robin Murphy
2021-08-13 17:41     ` Marc Zyngier
2021-08-13 18:17       ` Robin Murphy
2021-08-14  9:38         ` Marc Zyngier
2021-08-12 19:02 ` [PATCH 3/5] arm64: Detect disabled HVC early Marc Zyngier
2021-08-12 19:47   ` Rafał Miłecki
2021-08-13  9:05   ` Will Deacon
2021-08-13 17:33     ` Marc Zyngier
2021-08-12 19:02 ` [PATCH 4/5] arm64: Warn on booting at EL2 with HVC disabled Marc Zyngier
2021-08-12 19:58   ` Rafał Miłecki
2021-08-12 19:02 ` [PATCH 5/5] arm64: Document the requirement for SCR_EL3.HCE Marc Zyngier
2021-08-24 10:49   ` Catalin Marinas
2021-08-24 10:52     ` Mark Rutland
2021-08-15  7:28 ` [PATCH 0/5] arm64: Survival kit for SCR_EL3.HCE==0 conditions Florian Fainelli
2021-08-15  9:27   ` Marc Zyngier
2021-08-22 11:31     ` Florian Fainelli
2021-08-24 16:19 ` (subset) " Catalin Marinas

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