Commit 64b302ab authored by Dmitry Safonov's avatar Dmitry Safonov Committed by Thomas Gleixner
Browse files

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: default avatarAndrei Vagin <avagin@openvz.org>
Signed-off-by: default avatarAndrei Vagin <avagin@openvz.org>
Signed-off-by: default avatarDmitry Safonov <dima@arista.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20191112012724.250792-22-dima@arista.com
parent 660fd04f

arch/x86/entry/vdso/vdso-layout.lds.S

+0 −2
Original line number Diff line number Diff line
@@ -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 <asm/vvar.h>

#undef __VVAR_KERNEL_LDS

#undef EMIT_VVAR



	pvclock_page = vvar_start + PAGE_SIZE;

arch/x86/entry/vdso/vma.c

+11 −0
Original line number Diff line number Diff line
@@ -24,6 +24,17 @@ 
#include <asm/cpufeature.h>

#include <clocksource/hyperv_timer.h>



#undef _ASM_X86_VVAR_H

#define EMIT_VVAR(name, offset)	\

	const size_t name ## _offset = offset;

#include <asm/vvar.h>



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

arch/x86/include/asm/vvar.h

+4 −4
Original line number Diff line number Diff line
@@ -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)

arch/x86/kernel/vmlinux.lds.S

+1 −3
Original line number Diff line number Diff line
@@ -196,9 +196,7 @@ SECTIONS 
#define EMIT_VVAR(name, offset)				\

		. = __vvar_beginning_hack + offset;	\

		*(.vvar_ ## name)

#define __VVAR_KERNEL_LDS

#include <asm/vvar.h>

#undef __VVAR_KERNEL_LDS

#undef EMIT_VVAR



		/*

include/linux/time_namespace.h

+1 −0
Original line number Diff line number Diff line
@@ -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)

{

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