Messages in this thread |  | | Subject | Re: [PATCH 5/5] arm64/vdso: Restrict splitting VVAR VMA | From | Vincenzo Frascino <> | Date | Thu, 20 Feb 2020 12:22:52 +0000 |
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Hi Andrei,
On 04/02/2020 17:59, Andrei Vagin wrote: > Forbid splitting VVAR VMA resulting in a stricter ABI and reducing the > amount of corner-cases to consider while working further on VDSO time > namespace support. > > As the offset from timens to VVAR page is computed compile-time, the pages > in VVAR should stay together and not being partically mremap()'ed. >
I agree on the concept, but why do we need to redefine mremap? special_mapping_mremap() (mm/mmap.c +3317) seems doing already the same thing if we leave mremap == NULL as is.
> Signed-off-by: Andrei Vagin <avagin@gmail.com> > --- > arch/arm64/kernel/vdso.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c > index 2e553468b183..e6ebdc184c1e 100644 > --- a/arch/arm64/kernel/vdso.c > +++ b/arch/arm64/kernel/vdso.c > @@ -229,6 +229,17 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, > return vmf_insert_pfn(vma, vmf->address, pfn); > } > > +static int vvar_mremap(const struct vm_special_mapping *sm, > + struct vm_area_struct *new_vma) > +{ > + unsigned long new_size = new_vma->vm_end - new_vma->vm_start; > + > + if (new_size != VVAR_NR_PAGES * PAGE_SIZE) > + return -EINVAL; > + > + return 0; > +} > + > static int __setup_additional_pages(enum arch_vdso_type arch_index, > struct mm_struct *mm, > struct linux_binprm *bprm, > @@ -311,6 +322,7 @@ static struct vm_special_mapping aarch32_vdso_spec[C_PAGES] = { > { > .name = "[vvar]", > .fault = vvar_fault, > + .mremap = vvar_mremap, > }, > { > .name = "[vdso]", > @@ -493,6 +505,7 @@ static struct vm_special_mapping vdso_spec[A_PAGES] __ro_after_init = { > { > .name = "[vvar]", > .fault = vvar_fault, > + .mremap = vvar_mremap, > }, > { > .name = "[vdso]", >
-- Regards, Vincenzo [unhandled content-type:application/pgp-keys] |  |