Messages in this thread Patch in this message |  | | Subject | Re: [PATCH 3/5] arm64/vdso: Add time napespace page | From | Vincenzo Frascino <> | Date | Thu, 20 Feb 2020 12:03:27 +0000 |
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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__ */ > >
-- Regards, Vincenzo [unhandled content-type:application/pgp-keys] |  |