arm64: add the time namespace support

PATCH Superseded Andrei Vagin 3 participants 25 messages Feb 25, 2020 – Apr 15, 2020

Subsystems (2)

arm64 Generic VDSO library

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Andrei Vagin

author

2020-02-25 07:37 UTC #0 lore raw

v2 cover arm64: add the time namespace support

Allocate the time namespace page among VVAR pages and add the logic to handle faults on VVAR properly.

If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page. 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.

The extra check in the case that vdso_data->seq is odd, e.g. a concurrent update of the VDSO data is in progress, is not really affecting regular tasks which are not part of a time namespace as the task is spin waiting for the update to finish and vdso_data->seq to become even again.

If a time namespace task hits that code path, it invokes the corresponding time getter function which retrieves the real VVAR page, reads host time and then adds the offset for the requested clock which is stored in the special VVAR page.

v2: Code cleanups suggested by Vincenzo.

Cc Vincenzo Frascino <[email protected]>

Cc Thomas Gleixner <[email protected]>

Cc Dmitry Safonov <[email protected]>

Andrei Vagin (6):
arm64/vdso: use the fault callback to map vvar pages arm64/vdso: Zap vvar pages when switching to a time namespace arm64/vdso: Add time napespace page
arm64/vdso: Handle faults on timens page arm64/vdso: Restrict splitting VVAR VMA
arm64: enable time namespace support

 arch/arm64/Kconfig                            |   1 +
 .../include/asm/vdso/compat_gettimeofday.h    |  11 ++
 arch/arm64/include/asm/vdso/gettimeofday.h    |   8 ++
 arch/arm64/kernel/vdso.c                      | 134 ++++++++++++++++--
 arch/arm64/kernel/vdso/vdso.lds.S             |   3 +-
 arch/arm64/kernel/vdso32/vdso.lds.S           |   3 +-
 include/vdso/datapage.h                       |   1 +
 7 files changed, 147 insertions(+), 14 deletions(-)

Signature · 1 line

2.24.1

Andrei Vagin

author

2020-02-25 07:37 UTC #1 lore raw

PATCH v2 1/6 arm64/vdso: use the fault callback to map vvar pages

This is required to support time namespaces where a time namespace data page is different for each namespace.

Signed-off-by Andrei Vagin <[email protected]>

---
 arch/arm64/kernel/vdso.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

arch/arm64/kernel/vdso.c +15 -9

index 354b11e27c07..290c36d74e03 100644
@@ -114,28 +114,32 @@ static int __vdso_init(enum arch_vdso_type arch_index)
 			PAGE_SHIFT;
 
 	/* Allocate the vDSO pagelist, plus a page for the data. */
-	vdso_pagelist = kcalloc(vdso_lookup[arch_index].vdso_pages + 1,
+	vdso_pagelist = kcalloc(vdso_lookup[arch_index].vdso_pages,
 				sizeof(struct page *),
 				GFP_KERNEL);
 	if (vdso_pagelist == NULL)
 		return -ENOMEM;
 
-	/* Grab the vDSO data page. */
-	vdso_pagelist[0] = phys_to_page(__pa_symbol(vdso_data));
-
-
 	/* Grab the vDSO code pages. */
 	pfn = sym_to_pfn(vdso_lookup[arch_index].vdso_code_start);
 
 	for (i = 0; i < vdso_lookup[arch_index].vdso_pages; i++)
-		vdso_pagelist[i + 1] = pfn_to_page(pfn + i);
+		vdso_pagelist[i] = pfn_to_page(pfn + i);
 
-	vdso_lookup[arch_index].dm->pages = &vdso_pagelist[0];
-	vdso_lookup[arch_index].cm->pages = &vdso_pagelist[1];
+	vdso_lookup[arch_index].cm->pages = vdso_pagelist;
 
 	return 0;
 }
 
+static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
+			     struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+	if (vmf->pgoff == 0)
+		return vmf_insert_pfn(vma, vmf->address,
+				sym_to_pfn(vdso_data));
+	return VM_FAULT_SIGBUS;
+}
+
 static int __setup_additional_pages(enum arch_vdso_type arch_index,
 				    struct mm_struct *mm,
 				    struct linux_binprm *bprm,

@@ -155,7 +159,7 @@ static int __setup_additional_pages(enum arch_vdso_type arch_index,
 	}
 
 	ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
-				       VM_READ|VM_MAYREAD,
+				       VM_READ|VM_MAYREAD|VM_PFNMAP,
 				       vdso_lookup[arch_index].dm);
 	if (IS_ERR(ret))
 		goto up_fail;

@@ -215,6 +219,7 @@ static struct vm_special_mapping aarch32_vdso_spec[C_PAGES] = {
 #ifdef CONFIG_COMPAT_VDSO
 	{
 		.name = "[vvar]",
+		.fault = vvar_fault,
 	},
 	{
 		.name = "[vdso]",

@@ -396,6 +401,7 @@ static int vdso_mremap(const struct vm_special_mapping *sm,
 static struct vm_special_mapping vdso_spec[A_PAGES] __ro_after_init = {
 	{
 		.name	= "[vvar]",
+		.fault = vvar_fault,
 	},
 	{
 		.name	= "[vdso]",

Signature · 1 line

2.24.1

Vincenzo Frascino

maintainer Reviewed-by on v2 1/6

2020-04-09 12:00 UTC #2 lore raw

Re: [PATCH v2 1/6] arm64/vdso: use the fault callback to map vvar pages

Quoted 4 lines · Andrei Vagin

This is required to support time namespaces where a time namespace data page is different for each namespace.
Signed-off-by Andrei Vagin <[email protected]>

Reviewed-by Vincenzo Frascino <[email protected]>

Quoted 75 lines

---
 arch/arm64/kernel/vdso.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

arch/arm64/kernel/vdso.c +15 -9

index 354b11e27c07..290c36d74e03 100644
@@ -114,28 +114,32 @@ static int __vdso_init(enum arch_vdso_type arch_index)
 			PAGE_SHIFT;
 
 	/* Allocate the vDSO pagelist, plus a page for the data. */
-	vdso_pagelist = kcalloc(vdso_lookup[arch_index].vdso_pages + 1,
+	vdso_pagelist = kcalloc(vdso_lookup[arch_index].vdso_pages,
 				sizeof(struct page *),
 				GFP_KERNEL);
 	if (vdso_pagelist == NULL)
 		return -ENOMEM;
 
-	/* Grab the vDSO data page. */
-	vdso_pagelist[0] = phys_to_page(__pa_symbol(vdso_data));
-
-
 	/* Grab the vDSO code pages. */
 	pfn = sym_to_pfn(vdso_lookup[arch_index].vdso_code_start);
 
 	for (i = 0; i < vdso_lookup[arch_index].vdso_pages; i++)
-		vdso_pagelist[i + 1] = pfn_to_page(pfn + i);
+		vdso_pagelist[i] = pfn_to_page(pfn + i);
 
-	vdso_lookup[arch_index].dm->pages = &vdso_pagelist[0];
-	vdso_lookup[arch_index].cm->pages = &vdso_pagelist[1];
+	vdso_lookup[arch_index].cm->pages = vdso_pagelist;
 
 	return 0;
 }
 
+static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
+			     struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+	if (vmf->pgoff == 0)
+		return vmf_insert_pfn(vma, vmf->address,
+				sym_to_pfn(vdso_data));
+	return VM_FAULT_SIGBUS;
+}
+
 static int __setup_additional_pages(enum arch_vdso_type arch_index,
 				    struct mm_struct *mm,
 				    struct linux_binprm *bprm,

@@ -155,7 +159,7 @@ static int __setup_additional_pages(enum arch_vdso_type arch_index,
 	}
 
 	ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
-				       VM_READ|VM_MAYREAD,
+				       VM_READ|VM_MAYREAD|VM_PFNMAP,
 				       vdso_lookup[arch_index].dm);
 	if (IS_ERR(ret))
 		goto up_fail;

@@ -215,6 +219,7 @@ static struct vm_special_mapping aarch32_vdso_spec[C_PAGES] = {
 #ifdef CONFIG_COMPAT_VDSO
 	{
 		.name = "[vvar]",
+		.fault = vvar_fault,
 	},
 	{
 		.name = "[vdso]",

@@ -396,6 +401,7 @@ static int vdso_mremap(const struct vm_special_mapping *sm,
 static struct vm_special_mapping vdso_spec[A_PAGES] __ro_after_init = {
 	{
 		.name	= "[vvar]",
+		.fault = vvar_fault,
 	},
 	{
 		.name	= "[vdso]",

Signature · 2 lines

Regards,
Vincenzo

Andrei Vagin

author

2020-02-25 07:37 UTC #3 lore raw

PATCH v2 2/6 arm64/vdso: Zap vvar pages when switching to a time namespace

In reply to Andrei Vagin

The VVAR page layout depends on whether a task belongs to the root or non-root time namespace. Whenever a task changes its namespace, the VVAR page tables are cleared and then they will be re-faulted with a corresponding layout.

Signed-off-by Andrei Vagin <[email protected]>

---
 arch/arm64/kernel/vdso.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

arch/arm64/kernel/vdso.c +32 -0

index 290c36d74e03..6ac9cdeac5be 100644
@@ -131,6 +131,38 @@ static int __vdso_init(enum arch_vdso_type arch_index)
 	return 0;
 }
 
+#ifdef CONFIG_TIME_NS
+/*
+ * The vvar page layout depends on whether a task belongs to the root or
+ * non-root time namespace. Whenever a task changes its namespace, the VVAR
+ * page tables are cleared and then they will re-faulted with a
+ * corresponding layout.
+ * See also the comment near timens_setup_vdso_data() for details.
+ */
+int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
+{
+	struct mm_struct *mm = task->mm;
+	struct vm_area_struct *vma;
+
+	if (down_write_killable(&mm->mmap_sem))
+		return -EINTR;
+
+	for (vma = mm->mmap; vma; vma = vma->vm_next) {
+		unsigned long size = vma->vm_end - vma->vm_start;
+
+		if (vma_is_special_mapping(vma, vdso_lookup[ARM64_VDSO].dm))
+			zap_page_range(vma, vma->vm_start, size);
+#ifdef CONFIG_COMPAT_VDSO
+		if (vma_is_special_mapping(vma, vdso_lookup[ARM64_VDSO32].dm))
+			zap_page_range(vma, vma->vm_start, size);
+#endif
+	}
+
+	up_write(&mm->mmap_sem);
+	return 0;
+}
+#endif
+
 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 			     struct vm_area_struct *vma, struct vm_fault *vmf)
 {

Signature · 1 line

2.24.1

Vincenzo Frascino

maintainer Reviewed-by on v2 2/6

2020-04-09 12:01 UTC #4 lore raw

Re: [PATCH v2 2/6] arm64/vdso: Zap vvar pages when switching to a time namespace

Quoted 6 lines · Andrei Vagin

The VVAR page layout depends on whether a task belongs to the root or non-root time namespace. Whenever a task changes its namespace, the VVAR page tables are cleared and then they will be re-faulted with a corresponding layout.
Signed-off-by Andrei Vagin <[email protected]>

Reviewed-by Vincenzo Frascino <[email protected]>

Quoted 48 lines

---
 arch/arm64/kernel/vdso.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

arch/arm64/kernel/vdso.c +32 -0

index 290c36d74e03..6ac9cdeac5be 100644
@@ -131,6 +131,38 @@ static int __vdso_init(enum arch_vdso_type arch_index)
 	return 0;
 }
 
+#ifdef CONFIG_TIME_NS
+/*
+ * The vvar page layout depends on whether a task belongs to the root or
+ * non-root time namespace. Whenever a task changes its namespace, the VVAR
+ * page tables are cleared and then they will re-faulted with a
+ * corresponding layout.
+ * See also the comment near timens_setup_vdso_data() for details.
+ */
+int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
+{
+	struct mm_struct *mm = task->mm;
+	struct vm_area_struct *vma;
+
+	if (down_write_killable(&mm->mmap_sem))
+		return -EINTR;
+
+	for (vma = mm->mmap; vma; vma = vma->vm_next) {
+		unsigned long size = vma->vm_end - vma->vm_start;
+
+		if (vma_is_special_mapping(vma, vdso_lookup[ARM64_VDSO].dm))
+			zap_page_range(vma, vma->vm_start, size);
+#ifdef CONFIG_COMPAT_VDSO
+		if (vma_is_special_mapping(vma, vdso_lookup[ARM64_VDSO32].dm))
+			zap_page_range(vma, vma->vm_start, size);
+#endif
+	}
+
+	up_write(&mm->mmap_sem);
+	return 0;
+}
+#endif
+
 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 			     struct vm_area_struct *vma, struct vm_fault *vmf)
 {

Signature · 2 lines

Regards,
Vincenzo

Andrei Vagin

author

2020-02-25 07:37 UTC #5 lore raw

PATCH v2 3/6 arm64/vdso: Add time napespace page

In reply to Andrei Vagin

Allocate the time namespace page among VVAR pages. Provide __arch_get_timens_vdso_data() helper for VDSO code to get the code-relative position of VVARs on that special page.

Signed-off-by Andrei Vagin <[email protected]>

---
 arch/arm64/include/asm/vdso.h                 |  6 ++++++
 .../include/asm/vdso/compat_gettimeofday.h    | 11 ++++++++++
 arch/arm64/include/asm/vdso/gettimeofday.h    |  8 ++++++++
 arch/arm64/kernel/vdso.c                      | 20 ++++++++++++++++---
 arch/arm64/kernel/vdso/vdso.lds.S             |  5 ++++-
 arch/arm64/kernel/vdso32/vdso.lds.S           |  5 ++++-
 include/vdso/datapage.h                       |  1 +
 7 files changed, 51 insertions(+), 5 deletions(-)

arch/arm64/include/asm/vdso.h +6 -0

index 07468428fd29..351c145d3808 100644
@@ -12,6 +12,12 @@
  */
 #define VDSO_LBASE	0x0
 
+#ifdef CONFIG_TIME_NS
+#define __VVAR_PAGES    2
+#else
+#define __VVAR_PAGES    1
+#endif
+
 #ifndef __ASSEMBLY__
 
 #include <generated/vdso-offsets.h>

arch/arm64/include/asm/vdso/compat_gettimeofday.h +11 -0

index 81b0c394f1d8..042814339a63 100644
@@ -160,6 +160,17 @@ static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
 	return ret;
 }
 
+#ifdef CONFIG_TIME_NS
+static __always_inline const struct vdso_data *__arch_get_timens_vdso_data(void)
+{
+	const struct vdso_data *ret;
+
+	asm volatile("mov %0, %1" : "=r"(ret) : "r"(_timens_data));
+
+	return ret;
+}
+#endif
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_VDSO_GETTIMEOFDAY_H */

arch/arm64/include/asm/vdso/gettimeofday.h +8 -0

index 5a534432aa5d..553bdc19a91f 100644
@@ -97,6 +97,14 @@ const struct vdso_data *__arch_get_vdso_data(void)
 	return _vdso_data;
 }
 
+#ifdef CONFIG_TIME_NS
+static __always_inline
+const struct vdso_data *__arch_get_timens_vdso_data(void)
+{
+	return _timens_data;
+}
+#endif
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_VDSO_GETTIMEOFDAY_H */

arch/arm64/kernel/vdso.c +17 -3

index 6ac9cdeac5be..b3e7ce24e59b 100644
@@ -46,6 +46,14 @@ enum arch_vdso_type {
 #define VDSO_TYPES		(ARM64_VDSO + 1)
 #endif /* CONFIG_COMPAT_VDSO */
 
+enum vvar_pages {
+	VVAR_DATA_PAGE_OFFSET = 0,
+#ifdef CONFIG_TIME_NS
+	VVAR_TIMENS_PAGE_OFFSET = 1,
+#endif /* CONFIG_TIME_NS */
+	VVAR_NR_PAGES = __VVAR_PAGES,
+};
+
 struct __vdso_abi {
 	const char *name;
 	const char *vdso_code_start;

@@ -81,6 +89,12 @@ static union {
 } vdso_data_store __page_aligned_data;
 struct vdso_data *vdso_data = vdso_data_store.data;
 
+
+struct vdso_data *arch_get_vdso_data(void *vvar_page)
+{
+	return (struct vdso_data *)(vvar_page);
+}
+
 static int __vdso_remap(enum arch_vdso_type arch_index,
 			const struct vm_special_mapping *sm,
 			struct vm_area_struct *new_vma)

@@ -182,7 +196,7 @@ static int __setup_additional_pages(enum arch_vdso_type arch_index,
 
 	vdso_text_len = vdso_lookup[arch_index].vdso_pages << PAGE_SHIFT;
 	/* Be sure to map the data page */
-	vdso_mapping_len = vdso_text_len + PAGE_SIZE;
+	vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
 
 	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 	if (IS_ERR_VALUE(vdso_base)) {

@@ -190,13 +204,13 @@ static int __setup_additional_pages(enum arch_vdso_type arch_index,
 		goto up_fail;
 	}
 
-	ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
+	ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
 				       VM_READ|VM_MAYREAD|VM_PFNMAP,
 				       vdso_lookup[arch_index].dm);
 	if (IS_ERR(ret))
 		goto up_fail;
 
-	vdso_base += PAGE_SIZE;
+	vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
 	mm->context.vdso = (void *)vdso_base;
 	ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
 				       VM_READ|VM_EXEC|

arch/arm64/kernel/vdso/vdso.lds.S +4 -1

index 7ad2d3a0cd48..d808ad31e01f 100644
@@ -17,7 +17,10 @@ OUTPUT_ARCH(aarch64)
 
 SECTIONS
 {
-	PROVIDE(_vdso_data = . - PAGE_SIZE);
+	PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);
+#ifdef CONFIG_TIME_NS
+	PROVIDE(_timens_data = _vdso_data + PAGE_SIZE);
+#endif
 	. = VDSO_LBASE + SIZEOF_HEADERS;
 
 	.hash		: { *(.hash) }			:text

arch/arm64/kernel/vdso32/vdso.lds.S +4 -1

index a3944927eaeb..06cc60a9630f 100644
@@ -17,7 +17,10 @@ OUTPUT_ARCH(arm)
 
 SECTIONS
 {
-	PROVIDE_HIDDEN(_vdso_data = . - PAGE_SIZE);
+	PROVIDE_HIDDEN(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);
+#ifdef CONFIG_TIME_NS
+	PROVIDE_HIDDEN(_timens_data = _vdso_data + PAGE_SIZE);
+#endif
 	. = VDSO_LBASE + SIZEOF_HEADERS;
 
 	.hash		: { *(.hash) }			:text

include/vdso/datapage.h +1 -0

index 30c4cb0428d1..3494b5536b63 100644
@@ -98,6 +98,7 @@ struct vdso_data {
  * relocation, and this is what we need.
  */
 extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
+extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden")));
 
 #endif /* !__ASSEMBLY__ */

Signature · 1 line

2.24.1

Vincenzo Frascino

maintainer Reviewed-by on v2 3/6

2020-04-09 12:02 UTC #6 lore raw

Re: [PATCH v2 3/6] arm64/vdso: Add time napespace page

Quoted 15 lines · Andrei Vagin

Allocate the time namespace page among VVAR pages. Provide __arch_get_timens_vdso_data() helper for VDSO code to get the code-relative position of VVARs on that special page.
If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page. 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.
The extra check in the case that vdso_data->seq is odd, e.g. a concurrent update of the VDSO data is in progress, is not really affecting regular tasks which are not part of a time namespace as the task is spin waiting for the update to finish and vdso_data->seq to become even again.

Quoted 6 lines

If a time namespace task hits that code path, it invokes the corresponding time getter function which retrieves the real VVAR page, reads host time and then adds the offset for the requested clock which is stored in the special VVAR page.
Signed-off-by Andrei Vagin <[email protected]>

Reviewed-by Vincenzo Frascino <[email protected]>

Quoted 170 lines

---
 arch/arm64/include/asm/vdso.h                 |  6 ++++++
 .../include/asm/vdso/compat_gettimeofday.h    | 11 ++++++++++
 arch/arm64/include/asm/vdso/gettimeofday.h    |  8 ++++++++
 arch/arm64/kernel/vdso.c                      | 20 ++++++++++++++++---
 arch/arm64/kernel/vdso/vdso.lds.S             |  5 ++++-
 arch/arm64/kernel/vdso32/vdso.lds.S           |  5 ++++-
 include/vdso/datapage.h                       |  1 +
 7 files changed, 51 insertions(+), 5 deletions(-)

arch/arm64/include/asm/vdso.h +6 -0

index 07468428fd29..351c145d3808 100644
@@ -12,6 +12,12 @@
  */
 #define VDSO_LBASE	0x0
 
+#ifdef CONFIG_TIME_NS
+#define __VVAR_PAGES    2
+#else
+#define __VVAR_PAGES    1
+#endif
+
 #ifndef __ASSEMBLY__
 
 #include <generated/vdso-offsets.h>

arch/arm64/include/asm/vdso/compat_gettimeofday.h +11 -0

index 81b0c394f1d8..042814339a63 100644
@@ -160,6 +160,17 @@ static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
 	return ret;
 }
 
+#ifdef CONFIG_TIME_NS
+static __always_inline const struct vdso_data *__arch_get_timens_vdso_data(void)
+{
+	const struct vdso_data *ret;
+
+	asm volatile("mov %0, %1" : "=r"(ret) : "r"(_timens_data));
+
+	return ret;
+}
+#endif
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_VDSO_GETTIMEOFDAY_H */

arch/arm64/include/asm/vdso/gettimeofday.h +8 -0

index 5a534432aa5d..553bdc19a91f 100644
@@ -97,6 +97,14 @@ const struct vdso_data *__arch_get_vdso_data(void)
 	return _vdso_data;
 }
 
+#ifdef CONFIG_TIME_NS
+static __always_inline
+const struct vdso_data *__arch_get_timens_vdso_data(void)
+{
+	return _timens_data;
+}
+#endif
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_VDSO_GETTIMEOFDAY_H */

arch/arm64/kernel/vdso.c +17 -3

index 6ac9cdeac5be..b3e7ce24e59b 100644
@@ -46,6 +46,14 @@ enum arch_vdso_type {
 #define VDSO_TYPES		(ARM64_VDSO + 1)
 #endif /* CONFIG_COMPAT_VDSO */
 
+enum vvar_pages {
+	VVAR_DATA_PAGE_OFFSET = 0,
+#ifdef CONFIG_TIME_NS
+	VVAR_TIMENS_PAGE_OFFSET = 1,
+#endif /* CONFIG_TIME_NS */
+	VVAR_NR_PAGES = __VVAR_PAGES,
+};
+
 struct __vdso_abi {
 	const char *name;
 	const char *vdso_code_start;

@@ -81,6 +89,12 @@ static union {
 } vdso_data_store __page_aligned_data;
 struct vdso_data *vdso_data = vdso_data_store.data;
 
+
+struct vdso_data *arch_get_vdso_data(void *vvar_page)
+{
+	return (struct vdso_data *)(vvar_page);
+}
+
 static int __vdso_remap(enum arch_vdso_type arch_index,
 			const struct vm_special_mapping *sm,
 			struct vm_area_struct *new_vma)

@@ -182,7 +196,7 @@ static int __setup_additional_pages(enum arch_vdso_type arch_index,
 
 	vdso_text_len = vdso_lookup[arch_index].vdso_pages << PAGE_SHIFT;
 	/* Be sure to map the data page */
-	vdso_mapping_len = vdso_text_len + PAGE_SIZE;
+	vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
 
 	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 	if (IS_ERR_VALUE(vdso_base)) {

@@ -190,13 +204,13 @@ static int __setup_additional_pages(enum arch_vdso_type arch_index,
 		goto up_fail;
 	}
 
-	ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
+	ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
 				       VM_READ|VM_MAYREAD|VM_PFNMAP,
 				       vdso_lookup[arch_index].dm);
 	if (IS_ERR(ret))
 		goto up_fail;
 
-	vdso_base += PAGE_SIZE;
+	vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
 	mm->context.vdso = (void *)vdso_base;
 	ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
 				       VM_READ|VM_EXEC|

arch/arm64/kernel/vdso/vdso.lds.S +4 -1

index 7ad2d3a0cd48..d808ad31e01f 100644
@@ -17,7 +17,10 @@ OUTPUT_ARCH(aarch64)
 
 SECTIONS
 {
-	PROVIDE(_vdso_data = . - PAGE_SIZE);
+	PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);
+#ifdef CONFIG_TIME_NS
+	PROVIDE(_timens_data = _vdso_data + PAGE_SIZE);
+#endif
 	. = VDSO_LBASE + SIZEOF_HEADERS;
 
 	.hash		: { *(.hash) }			:text

arch/arm64/kernel/vdso32/vdso.lds.S +4 -1

index a3944927eaeb..06cc60a9630f 100644
@@ -17,7 +17,10 @@ OUTPUT_ARCH(arm)
 
 SECTIONS
 {
-	PROVIDE_HIDDEN(_vdso_data = . - PAGE_SIZE);
+	PROVIDE_HIDDEN(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);
+#ifdef CONFIG_TIME_NS
+	PROVIDE_HIDDEN(_timens_data = _vdso_data + PAGE_SIZE);
+#endif
 	. = VDSO_LBASE + SIZEOF_HEADERS;
 
 	.hash		: { *(.hash) }			:text

include/vdso/datapage.h +1 -0

index 30c4cb0428d1..3494b5536b63 100644
@@ -98,6 +98,7 @@ struct vdso_data {
  * relocation, and this is what we need.
  */
 extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
+extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden")));
 
 #endif /* !__ASSEMBLY__ */

Signature · 2 lines

Regards,
Vincenzo

Mark Rutland

reviewer

2020-04-14 17:20 UTC #7 lore raw

Re: [PATCH v2 3/6] arm64/vdso: Add time napespace page

In reply to Andrei Vagin

Quoted 31 lines · Andrei Vagin

Allocate the time namespace page among VVAR pages. Provide __arch_get_timens_vdso_data() helper for VDSO code to get the code-relative position of VVARs on that special page.
If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page. 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.
The extra check in the case that vdso_data->seq is odd, e.g. a concurrent update of the VDSO data is in progress, is not really affecting regular tasks which are not part of a time namespace as the task is spin waiting for the update to finish and vdso_data->seq to become even again.
If a time namespace task hits that code path, it invokes the corresponding time getter function which retrieves the real VVAR page, reads host time and then adds the offset for the requested clock which is stored in the special VVAR page.
Signed-off-by Andrei Vagin <[email protected]>
---
 arch/arm64/include/asm/vdso.h                 |  6 ++++++
 .../include/asm/vdso/compat_gettimeofday.h    | 11 ++++++++++
 arch/arm64/include/asm/vdso/gettimeofday.h    |  8 ++++++++
 arch/arm64/kernel/vdso.c                      | 20 ++++++++++++++++---
 arch/arm64/kernel/vdso/vdso.lds.S             |  5 ++++-
 arch/arm64/kernel/vdso32/vdso.lds.S           |  5 ++++-
 include/vdso/datapage.h                       |  1 +
 7 files changed, 51 insertions(+), 5 deletions(-)

arch/arm64/include/asm/vdso/compat_gettimeofday.h static __always_inline const struct vdso_data *__arch_get_vdso_data(void) · line 172

Quoted 10 lines

arch/arm64/include/asm/vdso/compat_gettimeofday.h +10 -0

+#ifdef CONFIG_TIME_NS
+static __always_inline const struct vdso_data *__arch_get_timens_vdso_data(void)
+{
+	const struct vdso_data *ret;
+
+	asm volatile("mov %0, %1" : "=r"(ret) : "r"(_timens_data));
+
+	return ret;
+}
+#endif

What is this inline assembly for? The commit message doesn't mention it, there's no explanation here, and the native version doesn't do likewise so it seems rather surprising.

Thanks,
Mark.

Quoted 15 lines

arch/arm64/include/asm/vdso/gettimeofday.h +7 -0

index 5a534432aa5d..553bdc19a91f 100644
@@ -97,6 +97,14 @@ const struct vdso_data *__arch_get_vdso_data(void)
 	return _vdso_data;
 }
 
+#ifdef CONFIG_TIME_NS
+static __always_inline
+const struct vdso_data *__arch_get_timens_vdso_data(void)
+{
+	return _timens_data;
+}
+#endif

Andrei Vagin

author

2020-04-15 02:35 UTC #8 lore raw

Re: [PATCH v2 3/6] arm64/vdso: Add time napespace page

Quoted 33 lines · Mark Rutland

Quoted 30 lines · Andrei Vagin
Allocate the time namespace page among VVAR pages. Provide __arch_get_timens_vdso_data() helper for VDSO code to get the code-relative position of VVARs on that special page.
If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page. 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.
The extra check in the case that vdso_data->seq is odd, e.g. a concurrent update of the VDSO data is in progress, is not really affecting regular tasks which are not part of a time namespace as the task is spin waiting for the update to finish and vdso_data->seq to become even again.
If a time namespace task hits that code path, it invokes the corresponding time getter function which retrieves the real VVAR page, reads host time and then adds the offset for the requested clock which is stored in the special VVAR page.
Signed-off-by Andrei Vagin <[email protected]>
---
 arch/arm64/include/asm/vdso.h                 |  6 ++++++
 .../include/asm/vdso/compat_gettimeofday.h    | 11 ++++++++++
 arch/arm64/include/asm/vdso/gettimeofday.h    |  8 ++++++++
 arch/arm64/kernel/vdso.c                      | 20 ++++++++++++++++---
 arch/arm64/kernel/vdso/vdso.lds.S             |  5 ++++-
 arch/arm64/kernel/vdso32/vdso.lds.S           |  5 ++++-
 include/vdso/datapage.h                       |  1 +
 7 files changed, 51 insertions(+), 5 deletions(-)

Quoted 14 lines

arch/arm64/include/asm/vdso/compat_gettimeofday.h static __always_inline const struct vdso_data *__arch_get_vdso_data(void) · line 172
Quoted 10 lines
arch/arm64/include/asm/vdso/compat_gettimeofday.h +10 -0
+#ifdef CONFIG_TIME_NS
+static __always_inline const struct vdso_data *__arch_get_timens_vdso_data(void)
+{
+     const struct vdso_data *ret;
+
+     asm volatile("mov %0, %1" : "=r"(ret) : "r"(_timens_data));
+
+     return ret;
+}
+#endif
What is this inline assembly for? The commit message doesn't mention it, there's no explanation here, and the native version doesn't do likewise so it seems rather surprising.

__arch_get_vdso_data is right before this function and there is a comment which explains this:
https://github.com/torvalds/linux/blob/master/arch/arm64/include/asm/vdso/compat_gettimeofday.h#L137

"""
/*
* This simply puts &_vdso_data into ret. The reason why we don't use
* ret = _vdso_data is that the compiler tends to optimize this in a
* very suboptimal way: instead of keeping &_vdso_data in a register,
* it goes through a relocation almost every time _vdso_data must be
* accessed (even in subfunctions). This is both time and space
* consuming: each relocation uses a word in the code section, and it
* has to be loaded at runtime.
*
* This trick hides the assignment from the compiler. Since it cannot
* track where the pointer comes from, it will only use one relocation
* where __arch_get_vdso_data() is called, and then keep the result in
* a register.
*/
"""

I decided to not duplicate the comment because these two functions are very similar and close to each other.

Thanks,
Andrei

_______________________________________________
linux-arm-kernel mailing list
[email protected]
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Mark Rutland

reviewer

2020-04-15 10:05 UTC #9 lore raw

Re: [PATCH v2 3/6] arm64/vdso: Add time napespace page

Quoted 70 lines · Andrei Vagin

Quoted 33 lines · Mark Rutland
Quoted 30 lines · Andrei Vagin
Allocate the time namespace page among VVAR pages. Provide __arch_get_timens_vdso_data() helper for VDSO code to get the code-relative position of VVARs on that special page.
If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page. 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.
The extra check in the case that vdso_data->seq is odd, e.g. a concurrent update of the VDSO data is in progress, is not really affecting regular tasks which are not part of a time namespace as the task is spin waiting for the update to finish and vdso_data->seq to become even again.
If a time namespace task hits that code path, it invokes the corresponding time getter function which retrieves the real VVAR page, reads host time and then adds the offset for the requested clock which is stored in the special VVAR page.
Signed-off-by Andrei Vagin <[email protected]>
---
 arch/arm64/include/asm/vdso.h                 |  6 ++++++
 .../include/asm/vdso/compat_gettimeofday.h    | 11 ++++++++++
 arch/arm64/include/asm/vdso/gettimeofday.h    |  8 ++++++++
 arch/arm64/kernel/vdso.c                      | 20 ++++++++++++++++---
 arch/arm64/kernel/vdso/vdso.lds.S             |  5 ++++-
 arch/arm64/kernel/vdso32/vdso.lds.S           |  5 ++++-
 include/vdso/datapage.h                       |  1 +
 7 files changed, 51 insertions(+), 5 deletions(-)
Quoted 14 lines
arch/arm64/include/asm/vdso/compat_gettimeofday.h static __always_inline const struct vdso_data *__arch_get_vdso_data(void) · line 172
Quoted 10 lines
arch/arm64/include/asm/vdso/compat_gettimeofday.h +10 -0
+#ifdef CONFIG_TIME_NS
+static __always_inline const struct vdso_data *__arch_get_timens_vdso_data(void)
+{
+     const struct vdso_data *ret;
+
+     asm volatile("mov %0, %1" : "=r"(ret) : "r"(_timens_data));
+
+     return ret;
+}
+#endif
What is this inline assembly for? The commit message doesn't mention it, there's no explanation here, and the native version doesn't do likewise so it seems rather surprising.
__arch_get_vdso_data is right before this function and there is a comment which explains this:
https://github.com/torvalds/linux/blob/master/arch/arm64/include/asm/vdso/compat_gettimeofday.h#L137
"""
/*
* This simply puts &_vdso_data into ret. The reason why we don't use
* ret = _vdso_data is that the compiler tends to optimize this in a
* very suboptimal way: instead of keeping &_vdso_data in a register,
* it goes through a relocation almost every time _vdso_data must be
* accessed (even in subfunctions). This is both time and space
* consuming: each relocation uses a word in the code section, and it
* has to be loaded at runtime.
*
* This trick hides the assignment from the compiler. Since it cannot
* track where the pointer comes from, it will only use one relocation
* where __arch_get_vdso_data() is called, and then keep the result in
* a register.
*/
"""

Quoted 2 lines

I decided to not duplicate the comment because these two functions are very similar and close to each other.

Ah, I was not aware of that context. Could we just add a trivial comment to say "see __arch_get_vdso_data" or something like that?

It's a shame we're not using OPTIMIZER_HIDE_VAR() for that, as it can generate slightly better code and is easier to read than bare asm.

Thanks,
Mark.

Vincenzo Frascino

maintainer

2020-04-15 10:15 UTC #10 lore raw

Re: [PATCH v2 3/6] arm64/vdso: Add time napespace page

Hi Mark,

Quoted 2 lines · Mark Rutland

It's a shame we're not using OPTIMIZER_HIDE_VAR() for that, as it can generate slightly better code and is easier to read than bare asm.

We are not because I was not aware when I wrote this code that such a macro existed :)

But you are right it clearly makes the code more readable. To make up for it, I am happy to make the effort to introduce it for both the cases and replace the assembler once this patch series gets merged.

Signature · 7 lines

Regards,
Vincenzo

_______________________________________________
linux-arm-kernel mailing list
[email protected]
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Mark Rutland

reviewer

2020-04-15 12:28 UTC #11 lore raw

Re: [PATCH v2 3/6] arm64/vdso: Add time napespace page

Quoted 6 lines · Vincenzo Frascino

Hi Mark,
Quoted 2 lines · Mark Rutland
It's a shame we're not using OPTIMIZER_HIDE_VAR() for that, as it can generate slightly better code and is easier to read than bare asm.

Quoted 6 lines

We are not because I was not aware when I wrote this code that such a macro existed :)
But you are right it clearly makes the code more readable. To make up for it, I am happy to make the effort to introduce it for both the cases and replace the assembler once this patch series gets merged.

Sounds good to me!

Mark.

_______________________________________________
linux-arm-kernel mailing list
[email protected]
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Andrei Vagin

author

2020-02-25 07:37 UTC #12 lore raw

PATCH v2 4/6 arm64/vdso: Handle faults on timens page

In reply to Andrei Vagin

If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page.

Signed-off-by Andrei Vagin <[email protected]>

---
 arch/arm64/kernel/vdso.c | 57 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 53 insertions(+), 4 deletions(-)

arch/arm64/kernel/vdso.c +53 -4

index b3e7ce24e59b..fb32c6f76078 100644
@@ -18,6 +18,7 @@
 #include <linux/sched.h>
 #include <linux/signal.h>
 #include <linux/slab.h>
+#include <linux/time_namespace.h>
 #include <linux/timekeeper_internal.h>
 #include <linux/vmalloc.h>
 #include <vdso/datapage.h>

@@ -175,15 +176,63 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 	up_write(&mm->mmap_sem);
 	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 inline 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)
 {
-	if (vmf->pgoff == 0)
-		return vmf_insert_pfn(vma, vmf->address,
-				sym_to_pfn(vdso_data));
-	return VM_FAULT_SIGBUS;
+	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 = sym_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 = sym_to_pfn(vdso_data);
+		break;
+#endif /* CONFIG_TIME_NS */
+	default:
+		return VM_FAULT_SIGBUS;
+	}
+
+	return vmf_insert_pfn(vma, vmf->address, pfn);
 }
 
 static int __setup_additional_pages(enum arch_vdso_type arch_index,

Signature · 1 line

2.24.1

Vincenzo Frascino

maintainer Reviewed-by on v2 4/6

2020-04-09 12:03 UTC #13 lore raw

Re: [PATCH v2 4/6] arm64/vdso: Handle faults on timens page

Quoted 5 lines · Andrei Vagin

If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page.
Signed-off-by Andrei Vagin <[email protected]>

Reviewed-by Vincenzo Frascino <[email protected]>

Quoted 85 lines

---
 arch/arm64/kernel/vdso.c | 57 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 53 insertions(+), 4 deletions(-)

arch/arm64/kernel/vdso.c +53 -4

index b3e7ce24e59b..fb32c6f76078 100644
@@ -18,6 +18,7 @@
 #include <linux/sched.h>
 #include <linux/signal.h>
 #include <linux/slab.h>
+#include <linux/time_namespace.h>
 #include <linux/timekeeper_internal.h>
 #include <linux/vmalloc.h>
 #include <vdso/datapage.h>

@@ -175,15 +176,63 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 	up_write(&mm->mmap_sem);
 	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 inline 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)
 {
-	if (vmf->pgoff == 0)
-		return vmf_insert_pfn(vma, vmf->address,
-				sym_to_pfn(vdso_data));
-	return VM_FAULT_SIGBUS;
+	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 = sym_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 = sym_to_pfn(vdso_data);
+		break;
+#endif /* CONFIG_TIME_NS */
+	default:
+		return VM_FAULT_SIGBUS;
+	}
+
+	return vmf_insert_pfn(vma, vmf->address, pfn);
 }
 
 static int __setup_additional_pages(enum arch_vdso_type arch_index,

Signature · 2 lines

Regards,
Vincenzo

Andrei Vagin

author

2020-02-25 07:37 UTC #14 lore raw

PATCH v2 5/6 arm64/vdso: Restrict splitting VVAR VMA

In reply to Andrei Vagin

Forbid splitting VVAR VMA resulting in a stricter ABI and reducing the amount of corner-cases to consider while working further on VDSO time namespace support.

As the offset from timens to VVAR page is computed compile-time, the pages in VVAR should stay together and not being partically mremap()'ed.

Signed-off-by Andrei Vagin <[email protected]>

---
 arch/arm64/kernel/vdso.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

arch/arm64/kernel/vdso.c +13 -0

index fb32c6f76078..c003f7ee383a 100644
@@ -235,6 +235,17 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 	return vmf_insert_pfn(vma, vmf->address, pfn);
 }
 
+static int vvar_mremap(const struct vm_special_mapping *sm,
+		       struct vm_area_struct *new_vma)
+{
+	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
+
+	if (new_size != VVAR_NR_PAGES * PAGE_SIZE)
+		return -EINVAL;
+
+	return 0;
+}
+
 static int __setup_additional_pages(enum arch_vdso_type arch_index,
 				    struct mm_struct *mm,
 				    struct linux_binprm *bprm,

@@ -315,6 +326,7 @@ static struct vm_special_mapping aarch32_vdso_spec[C_PAGES] = {
 	{
 		.name = "[vvar]",
 		.fault = vvar_fault,
+		.mremap = vvar_mremap,
 	},
 	{
 		.name = "[vdso]",

@@ -497,6 +509,7 @@ static struct vm_special_mapping vdso_spec[A_PAGES] __ro_after_init = {
 	{
 		.name	= "[vvar]",
 		.fault = vvar_fault,
+		.mremap = vvar_mremap,
 	},
 	{
 		.name	= "[vdso]",

Signature · 1 line

2.24.1

Vincenzo Frascino

maintainer Reviewed-by on v2 5/6

2020-04-09 12:04 UTC #15 lore raw

Re: [PATCH v2 5/6] arm64/vdso: Restrict splitting VVAR VMA

Quoted 8 lines · Andrei Vagin

Forbid splitting VVAR VMA resulting in a stricter ABI and reducing the amount of corner-cases to consider while working further on VDSO time namespace support.
As the offset from timens to VVAR page is computed compile-time, the pages in VVAR should stay together and not being partically mremap()'ed.
Signed-off-by Andrei Vagin <[email protected]>

Reviewed-by Vincenzo Frascino <[email protected]>

Quoted 43 lines

---
 arch/arm64/kernel/vdso.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

arch/arm64/kernel/vdso.c +13 -0

index fb32c6f76078..c003f7ee383a 100644
@@ -235,6 +235,17 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 	return vmf_insert_pfn(vma, vmf->address, pfn);
 }
 
+static int vvar_mremap(const struct vm_special_mapping *sm,
+		       struct vm_area_struct *new_vma)
+{
+	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
+
+	if (new_size != VVAR_NR_PAGES * PAGE_SIZE)
+		return -EINVAL;
+
+	return 0;
+}
+
 static int __setup_additional_pages(enum arch_vdso_type arch_index,
 				    struct mm_struct *mm,
 				    struct linux_binprm *bprm,

@@ -315,6 +326,7 @@ static struct vm_special_mapping aarch32_vdso_spec[C_PAGES] = {
 	{
 		.name = "[vvar]",
 		.fault = vvar_fault,
+		.mremap = vvar_mremap,
 	},
 	{
 		.name = "[vdso]",

@@ -497,6 +509,7 @@ static struct vm_special_mapping vdso_spec[A_PAGES] __ro_after_init = {
 	{
 		.name	= "[vvar]",
 		.fault = vvar_fault,
+		.mremap = vvar_mremap,
 	},
 	{
 		.name	= "[vdso]",

Signature · 2 lines

Regards,
Vincenzo

Andrei Vagin

author

2020-02-25 07:37 UTC #16 lore raw

PATCH v2 6/6 arm64: enable time namespace support

In reply to Andrei Vagin

CONFIG_TIME_NS is dependes on GENERIC_VDSO_TIME_NS.

Signed-off-by Andrei Vagin <[email protected]>

---
 arch/arm64/Kconfig | 1 +
 1 file changed, 1 insertion(+)

arch/arm64/Kconfig +1 -0

index c6c32fb7f546..660ad0b0e6bb 100644
@@ -110,6 +110,7 @@ config ARM64
 	select GENERIC_STRNLEN_USER
 	select GENERIC_TIME_VSYSCALL
 	select GENERIC_GETTIMEOFDAY
+	select GENERIC_VDSO_TIME_NS
 	select HANDLE_DOMAIN_IRQ
 	select HARDIRQS_SW_RESEND
 	select HAVE_PCI

Signature · 1 line

2.24.1

Vincenzo Frascino

maintainer Reviewed-by on v2 6/6

2020-04-09 12:05 UTC #17 lore raw

Re: [PATCH v2 6/6] arm64: enable time namespace support

Quoted 3 lines · Andrei Vagin

CONFIG_TIME_NS is dependes on GENERIC_VDSO_TIME_NS.
Signed-off-by Andrei Vagin <[email protected]>

Reviewed-by Vincenzo Frascino <[email protected]>

Quoted 17 lines

---
 arch/arm64/Kconfig | 1 +
 1 file changed, 1 insertion(+)

arch/arm64/Kconfig +1 -0

index c6c32fb7f546..660ad0b0e6bb 100644
@@ -110,6 +110,7 @@ config ARM64
 	select GENERIC_STRNLEN_USER
 	select GENERIC_TIME_VSYSCALL
 	select GENERIC_GETTIMEOFDAY
+	select GENERIC_VDSO_TIME_NS
 	select HANDLE_DOMAIN_IRQ
 	select HARDIRQS_SW_RESEND
 	select HAVE_PCI

Signature · 2 lines

Regards,
Vincenzo

Andrei Vagin

author

2020-04-01 06:50 UTC #18 lore raw

In reply to Andrei Vagin

Hi Vincenzo,

Have you had a chance to look at this series? Let me know if I need to rebase this patch set and resend it again.

Thanks,
Andrei

Vincenzo Frascino

maintainer

2020-04-01 09:01 UTC #19 lore raw

Hi Andrei,

Quoted 5 lines · Andrei Vagin

Hi Vincenzo,
Have you had a chance to look at this series? Let me know if I need to rebase this patch set and resend it again.

Sorry I still did not get the chance to have a look at your v2. I will try to do it by the end of this week, beginning of next.

Quoted 3 lines

Thanks,
Andrei

Signature · 2 lines

Regards,
Vincenzo

Vincenzo Frascino

maintainer

2020-04-09 13:23 UTC #20 lore raw

In reply to Andrei Vagin

Hi Andrei,

Quoted 14 lines · Andrei Vagin

Allocate the time namespace page among VVAR pages and add the logic to handle faults on VVAR properly.
If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page. 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.
The extra check in the case that vdso_data->seq is odd, e.g. a concurrent update of the VDSO data is in progress, is not really affecting regular tasks which are not part of a time namespace as the task is spin waiting for the update to finish and vdso_data->seq to become even again.

Quoted 7 lines

If a time namespace task hits that code path, it invokes the corresponding time getter function which retrieves the real VVAR page, reads host time and then adds the offset for the requested clock which is stored in the special VVAR page.
v2: Code cleanups suggested by Vincenzo.

Sorry for the delay, I completed this morning the review of your patches and I do not have anymore comments on them. Thank you for making the effort and bringing the time namespace support to arm64.

I have though a question on something I encountered during the testing of the
patches: I noticed that all the tests related to CLOCK_BOOTTIME_ALARM fail on arm64 (please find the results below the scissors). Is this expected?

--->8---

1..4
ok 1 clockid: 1 abs:0
ok 2 clockid: 1 abs:1
not ok 3 # error clock_gettime: Invalid argument
not ok 4 # error clock_gettime: Invalid argument Bail out!
# Pass 2 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 2
1..1
ok 1 exec
# Pass 1 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0
1..8
not ok 1 # error Warning: failed to find clock_gettime in vDSO

./timens.sh: line 5: 15382 Segmentation fault (core dumped) ./gettime_perf
1..1
ok 1 Passed for /proc/uptime
# Pass 1 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0
1..10
ok 1 Passed for CLOCK_BOOTTIME (syscall)
ok 2 Passed for CLOCK_BOOTTIME (vdso)
not ok 3 # error syscall(SYS_clock_gettime(9)): Invalid argument not ok 4 # error clock_gettime(9): Invalid argument
ok 5 Passed for CLOCK_MONOTONIC (syscall)
ok 6 Passed for CLOCK_MONOTONIC (vdso)
ok 7 Passed for CLOCK_MONOTONIC_COARSE (syscall)
ok 8 Passed for CLOCK_MONOTONIC_COARSE (vdso)
ok 9 Passed for CLOCK_MONOTONIC_RAW (syscall)
ok 10 Passed for CLOCK_MONOTONIC_RAW (vdso)
Bail out!
# Pass 8 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 2
1..3
ok 1 clockid=7
ok 2 clockid=1
not ok 3 # error timerfd_create: Operation not supported Bail out!
# Pass 2 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 1
1..3
ok 1 clockid=7
ok 2 clockid=1
ok 3 clockid=9
# Pass 3 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0

[...]

Signature · 2 lines

Regards,
Vincenzo

Andrei Vagin

author

2020-04-11 07:34 UTC #21 lore raw

Quoted 23 lines · Vincenzo Frascino

Hi Andrei,
Quoted 19 lines · Andrei Vagin
Allocate the time namespace page among VVAR pages and add the logic to handle faults on VVAR properly.
If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page. 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.
The extra check in the case that vdso_data->seq is odd, e.g. a concurrent update of the VDSO data is in progress, is not really affecting regular tasks which are not part of a time namespace as the task is spin waiting for the update to finish and vdso_data->seq to become even again.
If a time namespace task hits that code path, it invokes the corresponding time getter function which retrieves the real VVAR page, reads host time and then adds the offset for the requested clock which is stored in the special VVAR page.

Quoted 6 lines

Quoted 2 lines
v2: Code cleanups suggested by Vincenzo.
Sorry for the delay, I completed this morning the review of your patches and I do not have anymore comments on them. Thank you for making the effort and bringing the time namespace support to arm64.

Thank you for the review of these patches.

Quoted 4 lines

I have though a question on something I encountered during the testing of the
patches: I noticed that all the tests related to CLOCK_BOOTTIME_ALARM fail on arm64 (please find the results below the scissors). Is this expected?

static int alarm_clock_get_timespec(clockid_t which_clock, struct timespec64 *tp)

{
        struct alarm_base *base = &alarm_bases[clock2alarm(which_clock)];

        if (!alarmtimer_get_rtcdev())
                return -EINVAL;

It is probably that you get EINVAL from here ^^^. I will send a separate patch to handle this case in tests properly.

Thanks,
Andrei

Vincenzo Frascino

maintainer

2020-04-14 09:02 UTC #22 lore raw

Hi Andrei,

Quoted 5 lines · Andrei Vagin

Quoted 3 lines · Vincenzo Frascino
Hi Andrei,

[...]

Quoted 13 lines

Quoted 3 lines
Sorry for the delay, I completed this morning the review of your patches and I do not have anymore comments on them. Thank you for making the effort and bringing the time namespace support to arm64.
Thank you for the review of these patches.
Quoted 4 lines
I have though a question on something I encountered during the testing of the
patches: I noticed that all the tests related to CLOCK_BOOTTIME_ALARM fail on arm64 (please find the results below the scissors). Is this expected?
static int alarm_clock_get_timespec(clockid_t which_clock, struct timespec64 *tp)

Quoted 9 lines

{
        struct alarm_base *base = &alarm_bases[clock2alarm(which_clock)];

        if (!alarmtimer_get_rtcdev())
                return -EINVAL;
It is probably that you get EINVAL from here ^^^. I will send a separate patch to handle this case in tests properly.

This makes sense :) Please let me know when you post the fix so I can test it again.

Are you planning as well to rebase this set?

Quoted 3 lines

Thanks,
Andrei

Signature · 2 lines

Regards,
Vincenzo

Andrei Vagin

author

2020-04-15 16:15 UTC #23 lore raw

Quoted 16 lines · Vincenzo Frascino

Hi Andrei,
Quoted 12 lines · Andrei Vagin
Quoted 4 lines · Vincenzo Frascino
I have though a question on something I encountered during the testing of the
patches: I noticed that all the tests related to CLOCK_BOOTTIME_ALARM fail on arm64 (please find the results below the scissors). Is this expected?
static int alarm_clock_get_timespec(clockid_t which_clock, struct timespec64 *tp)
{
        struct alarm_base *base = &alarm_bases[clock2alarm(which_clock)];

Quoted 8 lines

Quoted 6 lines
        if (!alarmtimer_get_rtcdev())
                return -EINVAL;
It is probably that you get EINVAL from here ^^^. I will send a separate patch to handle this case in tests properly.
This makes sense :) Please let me know when you post the fix so I can test it again.

I have sent this fix: https://lkml.org/lkml/2020/4/15/72

Quoted 2 lines

Are you planning as well to rebase this set?

What is the right tree to rebase on?

Thanks,
Andrei

_______________________________________________
linux-arm-kernel mailing list
[email protected]
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Vincenzo Frascino

maintainer

2020-04-15 16:35 UTC #24 lore raw

Hi Andrei,

Quoted 21 lines · Andrei Vagin

Quoted 19 lines · Vincenzo Frascino
Hi Andrei,
Quoted 15 lines · Andrei Vagin
Quoted 4 lines · Vincenzo Frascino
I have though a question on something I encountered during the testing of the
patches: I noticed that all the tests related to CLOCK_BOOTTIME_ALARM fail on arm64 (please find the results below the scissors). Is this expected?
static int alarm_clock_get_timespec(clockid_t which_clock, struct timespec64 *tp)
{
        struct alarm_base *base = &alarm_bases[clock2alarm(which_clock)];

        if (!alarmtimer_get_rtcdev())
                return -EINVAL;

Quoted 8 lines

Quoted 5 lines
Quoted 3 lines
It is probably that you get EINVAL from here ^^^. I will send a separate patch to handle this case in tests properly.
This makes sense :) Please let me know when you post the fix so I can test it again.
I have sent this fix: https://lkml.org/lkml/2020/4/15/72

That's good, I will try it by the end of this week or beginning of next and let you know the results.

Quoted 4 lines

Quoted 2 lines
Are you planning as well to rebase this set?>
What is the right tree to rebase on?

I guess master, I was asking because it would make easier my testing :)

Quoted 3 lines

Thanks,
Andrei

Signature · 7 lines

Regards,
Vincenzo

_______________________________________________
linux-arm-kernel mailing list
[email protected]
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel