diff mbox series

[3/5] arm64/vdso: Add time napespace page

Message ID 20200204175913.74901-4-avagin@gmail.com (mailing list archive)
State New, archived
Headers show
Series arm64: add the time namespace support | expand

Commit Message

Andrei Vagin Feb. 4, 2020, 5:59 p.m. UTC 
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 <avagin@gmail.com>
---
 arch/arm64/Kconfig                               |  1 +
 .../arm64/include/asm/vdso/compat_gettimeofday.h | 11 +++++++++++
 arch/arm64/include/asm/vdso/gettimeofday.h       |  8 ++++++++
 arch/arm64/kernel/vdso.c                         | 16 +++++++++++++---
 arch/arm64/kernel/vdso/vdso.lds.S                |  3 ++-
 arch/arm64/kernel/vdso32/vdso.lds.S              |  3 ++-
 include/vdso/datapage.h                          |  1 +
 7 files changed, 38 insertions(+), 5 deletions(-)

Comments

Vincenzo Frascino Feb. 20, 2020, 12:03 p.m. UTC | #1 
Hi Andrei,

On 04/02/2020 17:59, Andrei Vagin wrote:
> 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 <avagin@gmail.com>
> ---
>  arch/arm64/Kconfig                               |  1 +
>  .../arm64/include/asm/vdso/compat_gettimeofday.h | 11 +++++++++++
>  arch/arm64/include/asm/vdso/gettimeofday.h       |  8 ++++++++
>  arch/arm64/kernel/vdso.c                         | 16 +++++++++++++---
>  arch/arm64/kernel/vdso/vdso.lds.S                |  3 ++-
>  arch/arm64/kernel/vdso32/vdso.lds.S              |  3 ++-
>  include/vdso/datapage.h                          |  1 +
>  7 files changed, 38 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index e688dfad0b72..a671c2e36e5f 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -109,6 +109,7 @@ 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

Could you please add the selection in a separate patch at the end of this series?

> diff --git a/arch/arm64/include/asm/vdso/compat_gettimeofday.h b/arch/arm64/include/asm/vdso/compat_gettimeofday.h
> index 537b1e695365..30a674f598c7 100644
> --- a/arch/arm64/include/asm/vdso/compat_gettimeofday.h
> +++ b/arch/arm64/include/asm/vdso/compat_gettimeofday.h
> @@ -161,6 +161,17 @@ 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 */
> diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h b/arch/arm64/include/asm/vdso/gettimeofday.h
> index b08f476b72b4..aa38e80dfbc4 100644
> --- a/arch/arm64/include/asm/vdso/gettimeofday.h
> +++ b/arch/arm64/include/asm/vdso/gettimeofday.h
> @@ -98,6 +98,14 @@ 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 */
> diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
> index 5ef808ddf08c..bc93e26ae485 100644
> --- a/arch/arm64/kernel/vdso.c
> +++ b/arch/arm64/kernel/vdso.c
> @@ -46,6 +46,10 @@ enum arch_vdso_type {
>  #define VDSO_TYPES		(ARM64_VDSO + 1)
>  #endif /* CONFIG_COMPAT_VDSO */
>  
> +#define VVAR_DATA_PAGE_OFFSET	0
> +#define VVAR_TIMENS_PAGE_OFFSET	1
> +#define VVAR_NR_PAGES		2
> +

Maybe we could change this in an enumeration. Something like:

enum vvar_pages {
	VVAR_DATA_PAGE_OFFSET = 0,
#ifdef CONFIG_TIME_NS
	VVAR_TIMENS_PAGE_OFFSET = 1,
#endif /* CONFIG_TIME_NS */
	VVAR_NR_PAGES = __VDSO_PAGES,
	(look at the change suggested below for vdso.h)
};

>  struct __vdso_abi {
>  	const char *name;
>  	const char *vdso_code_start;
> @@ -81,6 +85,12 @@ 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 +192,7 @@ 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 +200,13 @@ 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|
> diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
> index 7ad2d3a0cd48..a90b7d14e990 100644
> --- a/arch/arm64/kernel/vdso/vdso.lds.S
> +++ b/arch/arm64/kernel/vdso/vdso.lds.S
> @@ -17,7 +17,8 @@ OUTPUT_ARCH(aarch64)
>  
>  SECTIONS
>  {
> -	PROVIDE(_vdso_data = . - PAGE_SIZE);
> +	PROVIDE(_vdso_data = . - 2 * PAGE_SIZE);

Maybe we could have some conditional definition on CONFIG_TIME_NS in vdso.h:

#ifdef CONFIG_TIME_NS
#define __VVAR_PAGES	2
#else
#define __VVAR_PAGES 	1
#endif

and then here:

PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);

just to not forget what "2" stands for. What do you think?

> +	PROVIDE(_timens_data = _vdso_data + PAGE_SIZE);
>  	. = VDSO_LBASE + SIZEOF_HEADERS;
>  
>  	.hash		: { *(.hash) }			:text
> diff --git a/arch/arm64/kernel/vdso32/vdso.lds.S b/arch/arm64/kernel/vdso32/vdso.lds.S
> index a3944927eaeb..3e432b536e53 100644
> --- a/arch/arm64/kernel/vdso32/vdso.lds.S
> +++ b/arch/arm64/kernel/vdso32/vdso.lds.S
> @@ -17,7 +17,8 @@ OUTPUT_ARCH(arm)
>  
>  SECTIONS
>  {
> -	PROVIDE_HIDDEN(_vdso_data = . - PAGE_SIZE);
> +	PROVIDE_HIDDEN(_vdso_data = . - 2 * PAGE_SIZE);

Ditto.

> +	PROVIDE_HIDDEN(_timens_data = _vdso_data + PAGE_SIZE);
>  	. = VDSO_LBASE + SIZEOF_HEADERS;
>  
>  	.hash		: { *(.hash) }			:text
> diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
> index c5f347cc5e55..57eec6caca69 100644
> --- a/include/vdso/datapage.h
> +++ b/include/vdso/datapage.h
> @@ -100,6 +100,7 @@ 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__ */
>  
>
diff mbox series

Patch

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index e688dfad0b72..a671c2e36e5f 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -109,6 +109,7 @@  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
diff --git a/arch/arm64/include/asm/vdso/compat_gettimeofday.h b/arch/arm64/include/asm/vdso/compat_gettimeofday.h
index 537b1e695365..30a674f598c7 100644
--- a/arch/arm64/include/asm/vdso/compat_gettimeofday.h
+++ b/arch/arm64/include/asm/vdso/compat_gettimeofday.h
@@ -161,6 +161,17 @@  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 */
diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h b/arch/arm64/include/asm/vdso/gettimeofday.h
index b08f476b72b4..aa38e80dfbc4 100644
--- a/arch/arm64/include/asm/vdso/gettimeofday.h
+++ b/arch/arm64/include/asm/vdso/gettimeofday.h
@@ -98,6 +98,14 @@  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 */
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 5ef808ddf08c..bc93e26ae485 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -46,6 +46,10 @@  enum arch_vdso_type {
 #define VDSO_TYPES		(ARM64_VDSO + 1)
 #endif /* CONFIG_COMPAT_VDSO */
 
+#define VVAR_DATA_PAGE_OFFSET	0
+#define VVAR_TIMENS_PAGE_OFFSET	1
+#define VVAR_NR_PAGES		2
+
 struct __vdso_abi {
 	const char *name;
 	const char *vdso_code_start;
@@ -81,6 +85,12 @@  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 +192,7 @@  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 +200,13 @@  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|
diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
index 7ad2d3a0cd48..a90b7d14e990 100644
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S
@@ -17,7 +17,8 @@  OUTPUT_ARCH(aarch64)
 
 SECTIONS
 {
-	PROVIDE(_vdso_data = . - PAGE_SIZE);
+	PROVIDE(_vdso_data = . - 2 * PAGE_SIZE);
+	PROVIDE(_timens_data = _vdso_data + PAGE_SIZE);
 	. = VDSO_LBASE + SIZEOF_HEADERS;
 
 	.hash		: { *(.hash) }			:text
diff --git a/arch/arm64/kernel/vdso32/vdso.lds.S b/arch/arm64/kernel/vdso32/vdso.lds.S
index a3944927eaeb..3e432b536e53 100644
--- a/arch/arm64/kernel/vdso32/vdso.lds.S
+++ b/arch/arm64/kernel/vdso32/vdso.lds.S
@@ -17,7 +17,8 @@  OUTPUT_ARCH(arm)
 
 SECTIONS
 {
-	PROVIDE_HIDDEN(_vdso_data = . - PAGE_SIZE);
+	PROVIDE_HIDDEN(_vdso_data = . - 2 * PAGE_SIZE);
+	PROVIDE_HIDDEN(_timens_data = _vdso_data + PAGE_SIZE);
 	. = VDSO_LBASE + SIZEOF_HEADERS;
 
 	.hash		: { *(.hash) }			:text
diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index c5f347cc5e55..57eec6caca69 100644
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h
@@ -100,6 +100,7 @@  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__ */