linux-kernel - [PATCH v13 18/40] arm64/hwcap: Add hwcap for GCS

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Message-Id: <20241001-arm64-gcs-v13-18-222b78d87eee@kernel.org>
Date: Tue, 01 Oct 2024 23:58:57 +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>, 
 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>, Kees Cook <kees@...nel.org>
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>, 
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 Yury Khrustalev <yury.khrustalev@....com>, 
 Wilco Dijkstra <wilco.dijkstra@....com>, 
 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 v13 18/40] arm64/hwcap: Add hwcap for GCS

Provide a hwcap to enable userspace to detect support for GCS.

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 Documentation/arch/arm64/elf_hwcaps.rst | 4 ++++
 arch/arm64/include/asm/hwcap.h          | 1 +
 arch/arm64/include/uapi/asm/hwcap.h     | 3 ++-
 arch/arm64/kernel/cpufeature.c          | 3 +++
 arch/arm64/kernel/cpuinfo.c             | 1 +
 5 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Documentation/arch/arm64/elf_hwcaps.rst b/Documentation/arch/arm64/elf_hwcaps.rst
index 694f67fa07d1..25b41ff74fa0 100644
--- a/Documentation/arch/arm64/elf_hwcaps.rst
+++ b/Documentation/arch/arm64/elf_hwcaps.rst
@@ -170,6 +170,10 @@ HWCAP_PACG
     ID_AA64ISAR1_EL1.GPI == 0b0001, as described by
     Documentation/arch/arm64/pointer-authentication.rst.

+HWCAP_GCS
+    Functionality implied by ID_AA64PFR1_EL1.GCS == 0b1, as
+    described by Documentation/arch/arm64/gcs.rst.
+
 HWCAP2_DCPODP
     Functionality implied by ID_AA64ISAR1_EL1.DPB == 0b0010.

diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h
index a775adddecf2..7bcf1347ca0b 100644
--- a/arch/arm64/include/asm/hwcap.h
+++ b/arch/arm64/include/asm/hwcap.h
@@ -92,6 +92,7 @@
 #define KERNEL_HWCAP_SB			__khwcap_feature(SB)
 #define KERNEL_HWCAP_PACA		__khwcap_feature(PACA)
 #define KERNEL_HWCAP_PACG		__khwcap_feature(PACG)
+#define KERNEL_HWCAP_GCS		__khwcap_feature(GCS)

 #define __khwcap2_feature(x)		(const_ilog2(HWCAP2_ ## x) + 64)
 #define KERNEL_HWCAP_DCPODP		__khwcap2_feature(DCPODP)
diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
index 055381b2c615..675642ec4d91 100644
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -21,7 +21,7 @@
  * HWCAP flags - for AT_HWCAP
  *
  * Bits 62 and 63 are reserved for use by libc.
- * Bits 32-61 are unallocated for potential use by libc.
+ * Bits 33-61 are unallocated for potential use by libc.
  */
 #define HWCAP_FP		(1 << 0)
 #define HWCAP_ASIMD		(1 << 1)
@@ -55,6 +55,7 @@
 #define HWCAP_SB		(1 << 29)
 #define HWCAP_PACA		(1 << 30)
 #define HWCAP_PACG		(1UL << 31)
+#define HWCAP_GCS		(1UL << 32)

 /*
  * HWCAP2 flags - for AT_HWCAP2
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index d1e758e99e0a..b8655d55f318 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -3025,6 +3025,9 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
 	HWCAP_CAP(ID_AA64ZFR0_EL1, I8MM, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEI8MM),
 	HWCAP_CAP(ID_AA64ZFR0_EL1, F32MM, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEF32MM),
 	HWCAP_CAP(ID_AA64ZFR0_EL1, F64MM, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEF64MM),
+#endif
+#ifdef CONFIG_ARM64_GCS
+	HWCAP_CAP(ID_AA64PFR1_EL1, GCS, IMP, CAP_HWCAP, KERNEL_HWCAP_GCS),
 #endif
 	HWCAP_CAP(ID_AA64PFR1_EL1, SSBS, SSBS2, CAP_HWCAP, KERNEL_HWCAP_SSBS),
 #ifdef CONFIG_ARM64_BTI
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 44718d0482b3..f2f92c6b1c85 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -80,6 +80,7 @@ static const char *const hwcap_str[] = {
 	[KERNEL_HWCAP_SB]		= "sb",
 	[KERNEL_HWCAP_PACA]		= "paca",
 	[KERNEL_HWCAP_PACG]		= "pacg",
+	[KERNEL_HWCAP_GCS]		= "gcs",
 	[KERNEL_HWCAP_DCPODP]		= "dcpodp",
 	[KERNEL_HWCAP_SVE2]		= "sve2",
 	[KERNEL_HWCAP_SVEAES]		= "sveaes",

-- 
2.39.2