diff mbox series

[3/6] arm64/vdso: Add time namespace page

Message ID 20200602180259.76361-4-avagin@gmail.com (mailing list archive)
State New, archived
Headers show
Series arm64: add the time namespace support | expand

Commit Message

Andrei Vagin June 2, 2020, 6:02 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.

Cc: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
---
 arch/arm64/include/asm/vdso.h                 |  6 +++++
 .../include/asm/vdso/compat_gettimeofday.h    | 12 ++++++++++
 arch/arm64/include/asm/vdso/gettimeofday.h    |  8 +++++++
 arch/arm64/kernel/vdso.c                      | 22 ++++++++++++++++---
 arch/arm64/kernel/vdso/vdso.lds.S             |  5 ++++-
 arch/arm64/kernel/vdso32/vdso.lds.S           |  5 ++++-
 include/vdso/datapage.h                       |  1 +
 7 files changed, 54 insertions(+), 5 deletions(-)

Comments

Dmitry Safonov June 2, 2020, 7:29 p.m. UTC | #1 
Hi Andrei,

On 6/2/20 7:02 PM, Andrei Vagin wrote:
[..]
> --- a/arch/arm64/include/asm/vdso.h
> +++ b/arch/arm64/include/asm/vdso.h
> @@ -12,6 +12,12 @@
>   */
>  #define VDSO_LBASE	0x0
>  
> +#ifdef CONFIG_TIME_NS
> +#define __VVAR_PAGES    2
> +#else
> +#define __VVAR_PAGES    1
> +#endif
> +
>  #ifndef __ASSEMBLY__

Not an issue as-is, but:

on x86 vdso+vvar is always the same size with/without CONFIG_TIME_NAMESPACE.

Timens page isn't allocated on !CONFIG_TIME_NAMESPACE, but vma is the
same size. Which simplifies criu/vdso migration between different kernel
configs.

Not any critical, but just to note..

Thanks,
          Dima
kernel test robot June 2, 2020, 10:04 p.m. UTC | #2 
Hi Andrei,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on soc/for-next]
[also build test WARNING on arm/for-next kvmarm/next v5.7]
[cannot apply to arm64/for-next/core next-20200602]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Andrei-Vagin/arm64-add-the-time-namespace-support/20200603-020504
base:   https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git for-next
config: arm64-randconfig-r004-20200602 (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 2388a096e7865c043e83ece4e26654bd3d1a20d5)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm64 cross compiling tool for clang build
        # apt-get install binutils-aarch64-linux-gnu
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All warnings (new ones prefixed by >>, old ones prefixed by <<):

>> arch/arm64/kernel/vdso.c:93:19: warning: no previous prototype for function 'arch_get_vdso_data' [-Wmissing-prototypes]
struct vdso_data *arch_get_vdso_data(void *vvar_page)
^
arch/arm64/kernel/vdso.c:93:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
struct vdso_data *arch_get_vdso_data(void *vvar_page)
^
static
1 warning generated.

vim +/arch_get_vdso_data +93 arch/arm64/kernel/vdso.c

    91	
    92	
  > 93	struct vdso_data *arch_get_vdso_data(void *vvar_page)
    94	{
    95		return (struct vdso_data *)(vvar_page);
    96	}
    97	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
kernel test robot June 3, 2020, 6:42 a.m. UTC | #3 
Hi Andrei,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on soc/for-next]
[also build test WARNING on arm/for-next xlnx/master kvmarm/next v5.7]
[cannot apply to arm64/for-next/core next-20200602]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Andrei-Vagin/arm64-add-the-time-namespace-support/20200603-020504
base:   https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git for-next
config: arm64-allnoconfig (attached as .config)
compiler: aarch64-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=arm64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All warnings (new ones prefixed by >>, old ones prefixed by <<):

>> arch/arm64/kernel/vdso.c:93:19: warning: no previous prototype for 'arch_get_vdso_data' [-Wmissing-prototypes]
93 | struct vdso_data *arch_get_vdso_data(void *vvar_page)
|                   ^~~~~~~~~~~~~~~~~~

vim +/arch_get_vdso_data +93 arch/arm64/kernel/vdso.c

    91	
    92	
  > 93	struct vdso_data *arch_get_vdso_data(void *vvar_page)
    94	{
    95		return (struct vdso_data *)(vvar_page);
    96	}
    97	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
diff mbox series

Patch

diff --git a/arch/arm64/include/asm/vdso.h b/arch/arm64/include/asm/vdso.h
index 07468428fd29..351c145d3808 100644
--- a/arch/arm64/include/asm/vdso.h
+++ b/arch/arm64/include/asm/vdso.h
@@ -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>
diff --git a/arch/arm64/include/asm/vdso/compat_gettimeofday.h b/arch/arm64/include/asm/vdso/compat_gettimeofday.h
index b6907ae78e53..b7c549d46d18 100644
--- a/arch/arm64/include/asm/vdso/compat_gettimeofday.h
+++ b/arch/arm64/include/asm/vdso/compat_gettimeofday.h
@@ -152,6 +152,18 @@  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;
+
+	/* See __arch_get_vdso_data(). */
+	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 afba6ba332f8..cf39eae5eaaf 100644
--- a/arch/arm64/include/asm/vdso/gettimeofday.h
+++ b/arch/arm64/include/asm/vdso/gettimeofday.h
@@ -96,6 +96,14 @@  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 33df3cdf7982..1fa6f9362e56 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -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,
+#ifdef CONFIG_TIME_NS
+	VVAR_TIMENS_PAGE_OFFSET,
+#endif /* CONFIG_TIME_NS */
+	VVAR_NR_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)
@@ -180,9 +194,11 @@  static int __setup_additional_pages(enum arch_vdso_type arch_index,
 	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
 	void *ret;
 
+	BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
+
 	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 +206,13 @@  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..d808ad31e01f 100644
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S
@@ -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
diff --git a/arch/arm64/kernel/vdso32/vdso.lds.S b/arch/arm64/kernel/vdso32/vdso.lds.S
index a3944927eaeb..06cc60a9630f 100644
--- a/arch/arm64/kernel/vdso32/vdso.lds.S
+++ b/arch/arm64/kernel/vdso32/vdso.lds.S
@@ -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
diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index 7955c56d6b3c..ee810cae4e1e 100644
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h
@@ -109,6 +109,7 @@  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")));
 
 /*
  * The generic vDSO implementation requires that gettimeofday.h