Commit 74205b3f authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/vdso: Add support for time namespaces 



This patch adds the necessary glue to provide time namespaces.

Things are mainly copied from ARM64.

__arch_get_timens_vdso_data() calculates timens vdso data position
based on the vdso data position, knowing it is the next page in vvar.
This avoids having to redo the mflr/bcl/mflr/mtlr dance to locate
the page relative to running code position.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> # vDSO parts
Acked-by: default avatarAndrei Vagin <avagin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1a15495f80ec19a87b16cf874dbf7c3fa5ec40fe.1617209142.git.christophe.leroy@csgroup.eu
parent 1c4bce67

arch/powerpc/Kconfig

+2 −1
Original line number Diff line number Diff line
@@ -173,6 +173,7 @@ config PPC 
	select GENERIC_CPU_AUTOPROBE

	select GENERIC_CPU_VULNERABILITIES	if PPC_BARRIER_NOSPEC

	select GENERIC_EARLY_IOREMAP

	select GENERIC_GETTIMEOFDAY

	select GENERIC_IRQ_SHOW

	select GENERIC_IRQ_SHOW_LEVEL

	select GENERIC_PCI_IOMAP		if PCI
@@ -180,7 +181,7 @@ config PPC 
	select GENERIC_STRNCPY_FROM_USER

	select GENERIC_STRNLEN_USER

	select GENERIC_TIME_VSYSCALL

	select GENERIC_GETTIMEOFDAY

	select GENERIC_VDSO_TIME_NS

	select HAVE_ARCH_AUDITSYSCALL

	select HAVE_ARCH_HUGE_VMAP		if PPC_BOOK3S_64 && PPC_RADIX_MMU

	select HAVE_ARCH_JUMP_LABEL

arch/powerpc/include/asm/vdso/gettimeofday.h

+10 −0
Original line number Diff line number Diff line
@@ -2,6 +2,8 @@ 
#ifndef _ASM_POWERPC_VDSO_GETTIMEOFDAY_H

#define _ASM_POWERPC_VDSO_GETTIMEOFDAY_H



#include <asm/page.h>



#ifdef __ASSEMBLY__



#include <asm/ppc_asm.h>
@@ -154,6 +156,14 @@ static __always_inline u64 __arch_get_hw_counter(s32 clock_mode, 


const struct vdso_data *__arch_get_vdso_data(void);



#ifdef CONFIG_TIME_NS

static __always_inline

const struct vdso_data *__arch_get_timens_vdso_data(const struct vdso_data *vd)

{

	return (void *)vd + PAGE_SIZE;

}

#endif



static inline bool vdso_clocksource_ok(const struct vdso_data *vd)

{

	return true;

arch/powerpc/include/asm/vdso_datapage.h

+0 −2
Original line number Diff line number Diff line
@@ -107,9 +107,7 @@ extern struct vdso_arch_data *vdso_data; 
	bcl	20, 31, .+4

999:

	mflr	\ptr

#if CONFIG_PPC_PAGE_SHIFT > 14

	addis	\ptr, \ptr, (_vdso_datapage - 999b)@ha

#endif

	addi	\ptr, \ptr, (_vdso_datapage - 999b)@l

.endm

arch/powerpc/kernel/vdso.c

+100 −16
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <linux/security.h>

#include <linux/memblock.h>

#include <linux/syscalls.h>

#include <linux/time_namespace.h>

#include <vdso/datapage.h>



#include <asm/syscall.h>
@@ -50,6 +51,12 @@ static union { 
} vdso_data_store __page_aligned_data;

struct vdso_arch_data *vdso_data = &vdso_data_store.data;



enum vvar_pages {

	VVAR_DATA_PAGE_OFFSET,

	VVAR_TIMENS_PAGE_OFFSET,

	VVAR_NR_PAGES,

};



static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma,

		       unsigned long text_size)

{
@@ -73,8 +80,12 @@ static int vdso64_mremap(const struct vm_special_mapping *sm, struct vm_area_str 
	return vdso_mremap(sm, new_vma, &vdso64_end - &vdso64_start);

}



static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,

			     struct vm_area_struct *vma, struct vm_fault *vmf);



static struct vm_special_mapping vvar_spec __ro_after_init = {

	.name = "[vvar]",

	.fault = vvar_fault,

};



static struct vm_special_mapping vdso32_spec __ro_after_init = {
@@ -87,6 +98,94 @@ static struct vm_special_mapping vdso64_spec __ro_after_init = { 
	.mremap = vdso64_mremap,

};



#ifdef CONFIG_TIME_NS

struct vdso_data *arch_get_vdso_data(void *vvar_page)

{

	return ((struct vdso_arch_data *)vvar_page)->data;

}



/*

 * The vvar mapping contains data for a specific time namespace, so when a task

 * changes namespace we must unmap its vvar data for the old namespace.

 * Subsequent faults will map in data for the new namespace.

 *

 * For more details see timens_setup_vdso_data().

 */

int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)

{

	struct mm_struct *mm = task->mm;

	struct vm_area_struct *vma;



	mmap_read_lock(mm);



	for (vma = mm->mmap; vma; vma = vma->vm_next) {

		unsigned long size = vma->vm_end - vma->vm_start;



		if (vma_is_special_mapping(vma, &vvar_spec))

			zap_page_range(vma, vma->vm_start, size);

	}



	mmap_read_unlock(mm);

	return 0;

}



static struct page *find_timens_vvar_page(struct vm_area_struct *vma)

{

	if (likely(vma->vm_mm == current->mm))

		return current->nsproxy->time_ns->vvar_page;



	/*

	 * VM_PFNMAP | VM_IO protect .fault() handler from being called

	 * through interfaces like /proc/$pid/mem or

	 * process_vm_{readv,writev}() as long as there's no .access()

	 * in special_mapping_vmops.

	 * For more details check_vma_flags() and __access_remote_vm()

	 */

	WARN(1, "vvar_page accessed remotely");



	return NULL;

}

#else

static struct page *find_timens_vvar_page(struct vm_area_struct *vma)

{

	return NULL;

}

#endif



static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,

			     struct vm_area_struct *vma, struct vm_fault *vmf)

{

	struct page *timens_page = find_timens_vvar_page(vma);

	unsigned long pfn;



	switch (vmf->pgoff) {

	case VVAR_DATA_PAGE_OFFSET:

		if (timens_page)

			pfn = page_to_pfn(timens_page);

		else

			pfn = virt_to_pfn(vdso_data);

		break;

#ifdef CONFIG_TIME_NS

	case VVAR_TIMENS_PAGE_OFFSET:

		/*

		 * If a task belongs to a time namespace then a namespace

		 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and

		 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET

		 * offset.

		 * See also the comment near timens_setup_vdso_data().

		 */

		if (!timens_page)

			return VM_FAULT_SIGBUS;

		pfn = virt_to_pfn(vdso_data);

		break;

#endif /* CONFIG_TIME_NS */

	default:

		return VM_FAULT_SIGBUS;

	}



	return vmf_insert_pfn(vma, vmf->address, pfn);

}



/*

 * This is called from binfmt_elf, we create the special vma for the

 * vDSO and insert it into the mm struct tree
@@ -95,7 +194,7 @@ static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_int 
{

	unsigned long vdso_size, vdso_base, mappings_size;

	struct vm_special_mapping *vdso_spec;

	unsigned long vvar_size = PAGE_SIZE;

	unsigned long vvar_size = VVAR_NR_PAGES * PAGE_SIZE;

	struct mm_struct *mm = current->mm;

	struct vm_area_struct *vma;
@@ -266,19 +365,6 @@ static struct page ** __init vdso_setup_pages(void *start, void *end) 
	return pagelist;

}



static struct page ** __init vvar_setup_pages(void)

{

	struct page **pagelist;



	/* .pages is NULL-terminated */

	pagelist = kcalloc(2, sizeof(struct page *), GFP_KERNEL);

	if (!pagelist)

		panic("%s: Cannot allocate page list for VVAR", __func__);



	pagelist[0] = virt_to_page(vdso_data);

	return pagelist;

}



static int __init vdso_init(void)

{

#ifdef CONFIG_PPC64
@@ -317,8 +403,6 @@ static int __init vdso_init(void) 
	if (IS_ENABLED(CONFIG_PPC64))

		vdso64_spec.pages = vdso_setup_pages(&vdso64_start, &vdso64_end);



	vvar_spec.pages = vvar_setup_pages();



	smp_wmb();



	return 0;

arch/powerpc/kernel/vdso32/vdso32.lds.S

+1 −1
Original line number Diff line number Diff line
@@ -17,7 +17,7 @@ ENTRY(_start) 


SECTIONS

{

	PROVIDE(_vdso_datapage = . - PAGE_SIZE);

	PROVIDE(_vdso_datapage = . - 2 * PAGE_SIZE);

	. = SIZEOF_HEADERS;



	.hash          	: { *(.hash) }			:text