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authorAndrei Vagin <avagin@gmail.com>2020-06-24 01:33:18 -0700
committerCatalin Marinas <catalin.marinas@arm.com>2020-07-24 13:15:20 +0100
commit3503d56cc7233ced602e38a4c13caa64f00ab2aa (patch)
treebc7f29974127abc054e722d88dcd1a3c51750140 /arch/arm64
parent1b6867d2916bb91e94ddcc9c709e4779419fe391 (diff)
downloadlinux-3503d56cc7233ced602e38a4c13caa64f00ab2aa.tar.bz2
arm64/vdso: Add time namespace page
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. The time-namespace page isn't allocated on !CONFIG_TIME_NAMESPACE, but vma is the same size, which simplifies criu/vdso migration between different kernel configs. Signed-off-by: Andrei Vagin <avagin@gmail.com> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Reviewed-by: Dmitry Safonov <dima@arista.com> Cc: Mark Rutland <mark.rutland@arm.com> Link: https://lore.kernel.org/r/20200624083321.144975-4-avagin@gmail.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/include/asm/vdso.h2
-rw-r--r--arch/arm64/include/asm/vdso/compat_gettimeofday.h12
-rw-r--r--arch/arm64/include/asm/vdso/gettimeofday.h8
-rw-r--r--arch/arm64/kernel/vdso.c19
-rw-r--r--arch/arm64/kernel/vdso/vdso.lds.S5
-rw-r--r--arch/arm64/kernel/vdso32/vdso.lds.S5
6 files changed, 46 insertions, 5 deletions
diff --git a/arch/arm64/include/asm/vdso.h b/arch/arm64/include/asm/vdso.h
index 07468428fd29..f99dcb94b438 100644
--- a/arch/arm64/include/asm/vdso.h
+++ b/arch/arm64/include/asm/vdso.h
@@ -12,6 +12,8 @@
*/
#define VDSO_LBASE 0x0
+#define __VVAR_PAGES 2
+
#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 33ac18060bfc..fcb559726920 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -40,6 +40,12 @@ enum vdso_abi {
#endif /* CONFIG_COMPAT_VDSO */
};
+enum vvar_pages {
+ VVAR_DATA_PAGE_OFFSET,
+ VVAR_TIMENS_PAGE_OFFSET,
+ VVAR_NR_PAGES,
+};
+
struct vdso_abi_info {
const char *name;
const char *vdso_code_start;
@@ -125,6 +131,11 @@ static int __vdso_init(enum vdso_abi abi)
}
#ifdef CONFIG_TIME_NS
+struct vdso_data *arch_get_vdso_data(void *vvar_page)
+{
+ return (struct vdso_data *)(vvar_page);
+}
+
/*
* 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.
@@ -173,9 +184,11 @@ static int __setup_additional_pages(enum vdso_abi abi,
unsigned long gp_flags = 0;
void *ret;
+ BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
+
vdso_text_len = vdso_info[abi].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)) {
@@ -183,7 +196,7 @@ static int __setup_additional_pages(enum vdso_abi abi,
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_info[abi].dm);
if (IS_ERR(ret))
@@ -192,7 +205,7 @@ static int __setup_additional_pages(enum vdso_abi abi,
if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
gp_flags = VM_ARM64_BTI;
- 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|gp_flags|
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 337d03522048..3348ce5ea306 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