Messages in this thread |  | | Subject | Re: [PATCH 4/5] arm64/vdso: Handle faults on timens page | From | Vincenzo Frascino <> | Date | Thu, 20 Feb 2020 12:07:20 +0000 |
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Hi Andrei,
On 04/02/2020 17:59, Andrei Vagin wrote: > 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. > > Signed-off-by: Andrei Vagin <avagin@gmail.com> > --- > arch/arm64/kernel/vdso.c | 55 +++++++++++++++++++++++++++++++++++++--- > 1 file changed, 51 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c > index bc93e26ae485..2e553468b183 100644 > --- a/arch/arm64/kernel/vdso.c > +++ b/arch/arm64/kernel/vdso.c > @@ -23,6 +23,7 @@ > #include <vdso/datapage.h> > #include <vdso/helpers.h> > #include <vdso/vsyscall.h> > +#include <linux/time_namespace.h> >
Nit: Could you please group this with the linux/ headers and keep the alphabetical order.
> #include <asm/cacheflush.h> > #include <asm/signal32.h> > @@ -171,15 +172,61 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) > up_write(&mm->mmap_sem); > return 0; > } > + > +static struct page *find_timens_vvar_page(struct vm_area_struct *vma) > +{ > + if (likely(vma->vm_mm == current->mm)) > + return current->nsproxy->time_ns->vvar_page; > + > + /* > + * VM_PFNMAP | VM_IO protect .fault() handler from being called > + * through interfaces like /proc/$pid/mem or > + * process_vm_{readv,writev}() as long as there's no .access() > + * in special_mapping_vmops(). > + * For more details check_vma_flags() and __access_remote_vm() > + */ > + > + WARN(1, "vvar_page accessed remotely"); > + > + return NULL; > +} > +#else > +static inline struct page *find_timens_vvar_page(struct vm_area_struct *vma) > +{ > + return NULL; > +} > #endif > > static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, > struct vm_area_struct *vma, struct vm_fault *vmf) > { > - if (vmf->pgoff == 0) > - return vmf_insert_pfn(vma, vmf->address, > - sym_to_pfn(vdso_data)); > - return VM_FAULT_SIGBUS; > + struct page *timens_page = find_timens_vvar_page(vma); > + unsigned long pfn; > + > + switch (vmf->pgoff) { > + case VVAR_DATA_PAGE_OFFSET: > + if (timens_page) > + pfn = page_to_pfn(timens_page); > + else > + pfn = sym_to_pfn(vdso_data); > + break; > + case VVAR_TIMENS_PAGE_OFFSET: > + /* > + * If a task belongs to a time namespace then a namespace > + * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and > + * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET > + * offset. > + * See also the comment near timens_setup_vdso_data(). > + */ > + if (!timens_page) > + return VM_FAULT_SIGBUS; > + pfn = sym_to_pfn(vdso_data); > + break; > + default: > + return VM_FAULT_SIGBUS; > + } > + > + return vmf_insert_pfn(vma, vmf->address, pfn); > } > > static int __setup_additional_pages(enum arch_vdso_type arch_index, >
-- Regards, Vincenzo [unhandled content-type:application/pgp-keys] |  |