linux-kernel - [PATCH v2 13/35] arm64/el2_setup: Allow GCS usage at EL0 and EL1

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Message-Id: <20230724-arm64-gcs-v2-13-dc2c1d44c2eb@kernel.org>
Date:   Mon, 24 Jul 2023 13:46:00 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Arnd Bergmann <arnd@...db.de>, Oleg Nesterov <oleg@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Shuah Khan <shuah@...nel.org>,
        "Rick P. Edgecombe" <rick.p.edgecombe@...el.com>,
        Deepak Gupta <debug@...osinc.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Szabolcs Nagy <Szabolcs.Nagy@....com>
Cc:     "H.J. Lu" <hjl.tools@...il.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        kvmarm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, Mark Brown <broonie@...nel.org>
Subject: [PATCH v2 13/35] arm64/el2_setup: Allow GCS usage at EL0 and EL1

There is a control HCRX_EL2.GCSEn which must be set to allow GCS
features to take effect at lower ELs and also fine grained traps for GCS
usage at EL0 and EL1.  Configure all these to allow GCS usage by EL0 and
EL1.

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/include/asm/el2_setup.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
index 8e5ffb58f83e..45f3a7dcfd95 100644
--- a/arch/arm64/include/asm/el2_setup.h
+++ b/arch/arm64/include/asm/el2_setup.h
@@ -27,6 +27,14 @@
 	ubfx	x0, x0, #ID_AA64MMFR1_EL1_HCX_SHIFT, #4
 	cbz	x0, .Lskip_hcrx_\@
 	mov_q	x0, HCRX_HOST_FLAGS
+
+        /* Enable GCS if supported */
+	mrs_s	x1, SYS_ID_AA64PFR1_EL1
+	ubfx	x1, x1, #ID_AA64PFR1_EL1_GCS_SHIFT, #4
+	cbz	x1, .Lset_hcrx_\@
+	orr	x0, x0, #HCRX_EL2_GCSEn
+
+.Lset_hcrx_\@:
 	msr_s	SYS_HCRX_EL2, x0
 .Lskip_hcrx_\@:
 .endm
@@ -186,6 +194,15 @@
 	orr	x0, x0, #HFGxTR_EL2_nPIR_EL1
 	orr	x0, x0, #HFGxTR_EL2_nPIRE0_EL1
 
+	/* GCS depends on PIE so we don't check it if PIE is absent */
+	mrs_s	x1, SYS_ID_AA64PFR1_EL1
+	ubfx	x1, x1, #ID_AA64PFR1_EL1_GCS_SHIFT, #4
+	cbz	x1, .Lset_fgt_\@
+
+	/* Disable traps of access to GCS registers at EL0 and EL1 */
+	orr	x0, x0, #HFGxTR_EL2_nGCS_EL1_MASK
+	orr	x0, x0, #HFGxTR_EL2_nGCS_EL0_MASK
+
 .Lset_fgt_\@:
 	msr_s	SYS_HFGRTR_EL2, x0
 	msr_s	SYS_HFGWTR_EL2, x0

-- 
2.30.2