Messages in this thread | | | Subject | Re: [PATCH v2 3/6] arm64/vdso: Add time napespace page | From | Vincenzo Frascino <> | Date | Thu, 9 Apr 2020 13:03:03 +0100 |
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On 2/25/20 7:37 AM, 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>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> --- > 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(-) > > 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 81b0c394f1d8..042814339a63 100644 > --- a/arch/arm64/include/asm/vdso/compat_gettimeofday.h > +++ b/arch/arm64/include/asm/vdso/compat_gettimeofday.h > @@ -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 */ > diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h b/arch/arm64/include/asm/vdso/gettimeofday.h > index 5a534432aa5d..553bdc19a91f 100644 > --- a/arch/arm64/include/asm/vdso/gettimeofday.h > +++ b/arch/arm64/include/asm/vdso/gettimeofday.h > @@ -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 */ > diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c > index 6ac9cdeac5be..b3e7ce24e59b 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 = 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| > 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 30c4cb0428d1..3494b5536b63 100644 > --- a/include/vdso/datapage.h > +++ b/include/vdso/datapage.h > @@ -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__ */ > >
-- Regards, Vincenzo
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