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From: Mark Brown <broonie@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>, Andrei Vagin <avagin@gmail.com>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 04/11] arm64: vdso: Add getcpu() implementation
Date: Wed,  1 Jul 2020 21:28:39 +0100	[thread overview]
Message-ID: <20200701202846.54648-5-broonie@kernel.org> (raw)
In-Reply-To: <20200701202846.54648-1-broonie@kernel.org>

Some applications, especially trace ones, benefit from avoiding the syscall
overhead on getcpu() calls so provide a vDSO implementation of it.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/kernel/vdso/Makefile   |  2 +-
 arch/arm64/kernel/vdso/vdso.lds.S |  1 +
 arch/arm64/kernel/vdso/vgetcpu.c  | 48 +++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/kernel/vdso/vgetcpu.c

diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index 88cf0f0b91ed..ff350e69b8b6 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -11,7 +11,7 @@
 ARCH_REL_TYPE_ABS := R_AARCH64_JUMP_SLOT|R_AARCH64_GLOB_DAT|R_AARCH64_ABS64
 include $(srctree)/lib/vdso/Makefile
 
-obj-vdso := vgettimeofday.o note.o sigreturn.o
+obj-vdso := vgettimeofday.o note.o sigreturn.o vgetcpu.o
 
 # Build rules
 targets := $(obj-vdso) vdso.so vdso.so.dbg
diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
index 7ad2d3a0cd48..c2fd94f14b94 100644
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S
@@ -77,6 +77,7 @@ VERSION
 		__kernel_gettimeofday;
 		__kernel_clock_gettime;
 		__kernel_clock_getres;
+		__kernel_getcpu;
 	local: *;
 	};
 }
diff --git a/arch/arm64/kernel/vdso/vgetcpu.c b/arch/arm64/kernel/vdso/vgetcpu.c
new file mode 100644
index 000000000000..e8972e561e08
--- /dev/null
+++ b/arch/arm64/kernel/vdso/vgetcpu.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ARM64 userspace implementations of getcpu()
+ *
+ * Copyright (C) 2020 ARM Limited
+ *
+ */
+
+#include <asm/unistd.h>
+#include <asm/vdso/datapage.h>
+
+struct getcpucache;
+
+static __always_inline
+int getcpu_fallback(unsigned int *_cpu, unsigned int *_node,
+		    struct getcpucache *_c)
+{
+	register unsigned int *cpu asm("x0") = _cpu;
+	register unsigned int *node asm("x1") = _node;
+	register struct getcpucache *c asm("x2") = _c;
+	register long ret asm ("x0");
+	register long nr asm("x8") = __NR_getcpu;
+
+	asm volatile(
+	"       svc #0\n"
+	: "=r" (ret)
+	: "r" (cpu), "r" (node), "r" (c), "r" (nr)
+	: "memory");
+
+	return ret;
+}
+
+int __kernel_getcpu(unsigned int *cpu, unsigned int *node,
+		    struct getcpucache *c)
+{
+	struct vdso_cpu_data *cpu_data = __vdso_cpu_data();
+
+	if (cpu_data) {
+		if (cpu)
+			*cpu = cpu_data->cpu;
+		if (node)
+			*node = cpu_data->node;
+
+		return 0;
+	}
+
+	return getcpu_fallback(cpu, node, c);
+}
-- 
2.20.1


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  parent reply	other threads:[~2020-07-01 20:30 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-01 20:28 [PATCH v2 00/11] arm64: vdso: getcpu() support Mark Brown
2020-07-01 20:28 ` [PATCH v2 01/11] arm64: vdso: Provide a define when building the vDSO Mark Brown
2020-07-01 20:28 ` [PATCH v2 02/11] arm64: vdso: Add per-CPU data Mark Brown
2020-07-01 20:28 ` [PATCH v2 03/11] arm64: vdso: Initialise the per-CPU vDSO data Mark Brown
2020-07-01 20:28 ` Mark Brown [this message]
2020-07-01 20:28 ` [PATCH v2 05/11] arm64: vdso: Remove union in declaration of the data store Mark Brown
2020-07-01 20:28 ` [PATCH v2 06/11] arm64: vdso: Document and verify alignment of vDSO text Mark Brown
2020-07-01 20:28 ` [PATCH v2 07/11] arm64: vdso: Rename vdso_pages to vdso_text_pages Mark Brown
2020-07-01 20:28 ` [PATCH v2 08/11] arm64: vdso: Simplify pagelist allocation Mark Brown
2020-07-01 20:28 ` [PATCH v2 09/11] arm64: vdso: Parameterise vDSO data length assumptions in code Mark Brown
2020-07-01 20:28 ` [PATCH v2 10/11] arm64: vdso: Support multiple pages of vDSO data Mark Brown
2020-07-01 20:28 ` [PATCH v2 11/11] selftests: vdso: Support arm64 in getcpu() test Mark Brown

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