From 64b302ab66c5965702693e79690823ca120288b9 Mon Sep 17 00:00:00 2001 From: Dmitry Safonov Date: Tue, 12 Nov 2019 01:27:10 +0000 Subject: [PATCH] x86/vdso: Provide vdso_data offset on vvar_page VDSO support for time namespaces needs to set up a page with the same layout as VVAR. That timens page will be placed on position of VVAR page inside namespace. That page has vdso_data->seq set to 1 to enforce the slow path and vdso_data->clock_mode set to VCLOCK_TIMENS to enforce the time namespace handling path. To prepare the time namespace page the kernel needs to know the vdso_data offset. Provide arch_get_vdso_data() helper for locating vdso_data on VVAR page. Co-developed-by: Andrei Vagin Signed-off-by: Andrei Vagin Signed-off-by: Dmitry Safonov Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20191112012724.250792-22-dima@arista.com --- arch/x86/entry/vdso/vdso-layout.lds.S | 2 -- arch/x86/entry/vdso/vma.c | 11 +++++++++++ arch/x86/include/asm/vvar.h | 8 ++++---- arch/x86/kernel/vmlinux.lds.S | 4 +--- include/linux/time_namespace.h | 1 + 5 files changed, 17 insertions(+), 9 deletions(-) diff --git a/arch/x86/entry/vdso/vdso-layout.lds.S b/arch/x86/entry/vdso/vdso-layout.lds.S index 93c6dc7..2330daa 100644 --- a/arch/x86/entry/vdso/vdso-layout.lds.S +++ b/arch/x86/entry/vdso/vdso-layout.lds.S @@ -21,9 +21,7 @@ SECTIONS /* Place all vvars at the offsets in asm/vvar.h. */ #define EMIT_VVAR(name, offset) vvar_ ## name = vvar_page + offset; -#define __VVAR_KERNEL_LDS #include -#undef __VVAR_KERNEL_LDS #undef EMIT_VVAR pvclock_page = vvar_start + PAGE_SIZE; diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 76cbe54..04e3498 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -24,6 +24,17 @@ #include #include +#undef _ASM_X86_VVAR_H +#define EMIT_VVAR(name, offset) \ + const size_t name ## _offset = offset; +#include + +struct vdso_data *arch_get_vdso_data(void *vvar_page) +{ + return (struct vdso_data *)(vvar_page + _vdso_data_offset); +} +#undef EMIT_VVAR + #if defined(CONFIG_X86_64) unsigned int __read_mostly vdso64_enabled = 1; #endif diff --git a/arch/x86/include/asm/vvar.h b/arch/x86/include/asm/vvar.h index 32f5d9a..ff2de30 100644 --- a/arch/x86/include/asm/vvar.h +++ b/arch/x86/include/asm/vvar.h @@ -19,10 +19,10 @@ #ifndef _ASM_X86_VVAR_H #define _ASM_X86_VVAR_H -#if defined(__VVAR_KERNEL_LDS) - -/* The kernel linker script defines its own magic to put vvars in the - * right place. +#ifdef EMIT_VVAR +/* + * EMIT_VVAR() is used by the kernel linker script to put vvars in the + * right place. Also, it's used by kernel code to import offsets values. */ #define DECLARE_VVAR(offset, type, name) \ EMIT_VVAR(name, offset) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 3a1a819..e3296aa 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -193,12 +193,10 @@ SECTIONS __vvar_beginning_hack = .; /* Place all vvars at the offsets in asm/vvar.h. */ -#define EMIT_VVAR(name, offset) \ +#define EMIT_VVAR(name, offset) \ . = __vvar_beginning_hack + offset; \ *(.vvar_ ## name) -#define __VVAR_KERNEL_LDS #include -#undef __VVAR_KERNEL_LDS #undef EMIT_VVAR /* diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h index 34ee110..063a343 100644 --- a/include/linux/time_namespace.h +++ b/include/linux/time_namespace.h @@ -39,6 +39,7 @@ struct time_namespace *copy_time_ns(unsigned long flags, struct time_namespace *old_ns); void free_time_ns(struct kref *kref); int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk); +struct vdso_data *arch_get_vdso_data(void *vvar_page); static inline void put_time_ns(struct time_namespace *ns) { -- 2.7.4