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 d808ad31e01f..ef3fb80e0349 100644 --- a/arch/arm64/kernel/vdso/vdso.lds.S +++ b/arch/arm64/kernel/vdso/vdso.lds.S @@ -80,6 +80,7 @@ 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); +}