| Message ID | 20200616075545.312684-2-avagin@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: add the time namespace support | expand |
On Tue, Jun 16, 2020 at 12:55:40AM -0700, Andrei Vagin wrote: > This is required to support time namespaces where a time namespace data > page is different for each namespace. Can you please give a bit more of an introduction to the changes here? As-is, this doesn't give reviewers the necessary context to understand the change, nor does it justify it. Ideally, a commit message for this should look something like: | Currently the vdso has no awareness of time namespaces, which may | apply distinct offsets to processes in different namespaces. To handle | this within the vdso, we'll need to expose a per-namespace data page. | | As a preparatory step, this patch separates the vdso data page from | the code pages, and has it faulted in via its own fault callback. | Subsquent patches will extend this to support distinct pages per time | namespace. Otherwise, I have a few minor comments below. > Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> > Reviewed-by: Dmitry Safonov <dima@arista.com> > Signed-off-by: Andrei Vagin <avagin@gmail.com> > --- > arch/arm64/kernel/vdso.c | 24 +++++++++++++++--------- > 1 file changed, 15 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c > index 4e016574bd91..b0aec4e8c9b4 100644 > --- a/arch/arm64/kernel/vdso.c > +++ b/arch/arm64/kernel/vdso.c > @@ -108,28 +108,32 @@ static int __vdso_init(enum vdso_abi abi) > PAGE_SHIFT; > > /* Allocate the vDSO pagelist, plus a page for the data. */ > - vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages + 1, > + vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages, > sizeof(struct page *), > GFP_KERNEL); The comment above is now stale. Can you please update it, or (event better) delete it entirely? > if (vdso_pagelist == NULL) > return -ENOMEM; > > - /* Grab the vDSO data page. */ > - vdso_pagelist[0] = phys_to_page(__pa_symbol(vdso_data)); > - > - > /* Grab the vDSO code pages. */ > pfn = sym_to_pfn(vdso_info[abi].vdso_code_start); > > for (i = 0; i < vdso_info[abi].vdso_pages; i++) > - vdso_pagelist[i + 1] = pfn_to_page(pfn + i); > + vdso_pagelist[i] = pfn_to_page(pfn + i); > > - vdso_info[abi].dm->pages = &vdso_pagelist[0]; > - vdso_info[abi].cm->pages = &vdso_pagelist[1]; > + vdso_info[abi].cm->pages = vdso_pagelist; > > return 0; > } > > +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; > +} This might look better as: | if (vmf->pgoff != 0) | return VM_FAULT_SIGBUS; | | return vmf_insert_pfn(vma, vmf->address, sym_to_pfn(vdso_data)); > + > static int __setup_additional_pages(enum vdso_abi abi, > struct mm_struct *mm, > struct linux_binprm *bprm, > @@ -150,7 +154,7 @@ static int __setup_additional_pages(enum vdso_abi abi, > } > > ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE, > - VM_READ|VM_MAYREAD, > + VM_READ|VM_MAYREAD|VM_PFNMAP, This change needs to be explained in the commit message. WHy is it necessary, and why only so for the data page? Thanks, Mark. > vdso_info[abi].dm); > if (IS_ERR(ret)) > goto up_fail; > @@ -209,6 +213,7 @@ static struct vm_special_mapping aarch32_vdso_maps[] = { > #ifdef CONFIG_COMPAT_VDSO > [AA32_MAP_VVAR] = { > .name = "[vvar]", > + .fault = vvar_fault, > }, > [AA32_MAP_VDSO] = { > .name = "[vdso]", > @@ -376,6 +381,7 @@ enum aarch64_map { > static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = { > [AA64_MAP_VVAR] = { > .name = "[vvar]", > + .fault = vvar_fault, > }, > [AA64_MAP_VDSO] = { > .name = "[vdso]", > -- > 2.24.1 >
On Tue, Jun 16, 2020 at 11:59:20AM +0100, Mark Rutland wrote: > On Tue, Jun 16, 2020 at 12:55:40AM -0700, Andrei Vagin wrote: > > This is required to support time namespaces where a time namespace data > > page is different for each namespace. > > Can you please give a bit more of an introduction to the changes here? > As-is, this doesn't give reviewers the necessary context to understand > the change, nor does it justify it. > > Ideally, a commit message for this should look something like: Mark, thank you for the review. I will write more details message and fix this patch according with your other comments. > > | Currently the vdso has no awareness of time namespaces, which may > | apply distinct offsets to processes in different namespaces. To handle > | this within the vdso, we'll need to expose a per-namespace data page. > | > | As a preparatory step, this patch separates the vdso data page from > | the code pages, and has it faulted in via its own fault callback. > | Subsquent patches will extend this to support distinct pages per time > | namespace. > > Otherwise, I have a few minor comments below. > > > Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> > > Reviewed-by: Dmitry Safonov <dima@arista.com> > > Signed-off-by: Andrei Vagin <avagin@gmail.com> > > --- > > arch/arm64/kernel/vdso.c | 24 +++++++++++++++--------- > > 1 file changed, 15 insertions(+), 9 deletions(-) > > > > diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c > > index 4e016574bd91..b0aec4e8c9b4 100644 > > --- a/arch/arm64/kernel/vdso.c > > +++ b/arch/arm64/kernel/vdso.c > > @@ -108,28 +108,32 @@ static int __vdso_init(enum vdso_abi abi) > > PAGE_SHIFT; > > > > /* Allocate the vDSO pagelist, plus a page for the data. */ > > - vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages + 1, > > + vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages, > > sizeof(struct page *), > > GFP_KERNEL); > > The comment above is now stale. Can you please update it, or (event > better) delete it entirely? I will delete it. > > > if (vdso_pagelist == NULL) > > return -ENOMEM; > > > > - /* Grab the vDSO data page. */ > > - vdso_pagelist[0] = phys_to_page(__pa_symbol(vdso_data)); > > - > > - > > /* Grab the vDSO code pages. */ > > pfn = sym_to_pfn(vdso_info[abi].vdso_code_start); > > > > for (i = 0; i < vdso_info[abi].vdso_pages; i++) > > - vdso_pagelist[i + 1] = pfn_to_page(pfn + i); > > + vdso_pagelist[i] = pfn_to_page(pfn + i); > > > > - vdso_info[abi].dm->pages = &vdso_pagelist[0]; > > - vdso_info[abi].cm->pages = &vdso_pagelist[1]; > > + vdso_info[abi].cm->pages = vdso_pagelist; > > > > return 0; > > } > > > > +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; > > +} > > This might look better as: In the next patch, this function will handle more pages and this form will look better. > > | if (vmf->pgoff != 0) > | return VM_FAULT_SIGBUS; > | > | return vmf_insert_pfn(vma, vmf->address, sym_to_pfn(vdso_data)); > > > + > > static int __setup_additional_pages(enum vdso_abi abi, > > struct mm_struct *mm, > > struct linux_binprm *bprm, > > @@ -150,7 +154,7 @@ static int __setup_additional_pages(enum vdso_abi abi, > > } > > > > ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE, > > - VM_READ|VM_MAYREAD, > > + VM_READ|VM_MAYREAD|VM_PFNMAP, > > This change needs to be explained in the commit message. WHy is it > necessary, and why only so for the data page? I will update the commit message. VM_PFNMAP is required to handle faults from a vma fault callback. In this case, it is vvar_fault. > > Thanks, > Mark. > > > vdso_info[abi].dm); > > if (IS_ERR(ret)) > > goto up_fail; > > @@ -209,6 +213,7 @@ static struct vm_special_mapping aarch32_vdso_maps[] = { > > #ifdef CONFIG_COMPAT_VDSO > > [AA32_MAP_VVAR] = { > > .name = "[vvar]", > > + .fault = vvar_fault, > > }, > > [AA32_MAP_VDSO] = { > > .name = "[vdso]", > > @@ -376,6 +381,7 @@ enum aarch64_map { > > static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = { > > [AA64_MAP_VVAR] = { > > .name = "[vvar]", > > + .fault = vvar_fault, > > }, > > [AA64_MAP_VDSO] = { > > .name = "[vdso]", > > -- > > 2.24.1 > >
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c index 4e016574bd91..b0aec4e8c9b4 100644 --- a/arch/arm64/kernel/vdso.c +++ b/arch/arm64/kernel/vdso.c @@ -108,28 +108,32 @@ static int __vdso_init(enum vdso_abi abi) PAGE_SHIFT; /* Allocate the vDSO pagelist, plus a page for the data. */ - vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages + 1, + vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages, sizeof(struct page *), GFP_KERNEL); if (vdso_pagelist == NULL) return -ENOMEM; - /* Grab the vDSO data page. */ - vdso_pagelist[0] = phys_to_page(__pa_symbol(vdso_data)); - - /* Grab the vDSO code pages. */ pfn = sym_to_pfn(vdso_info[abi].vdso_code_start); for (i = 0; i < vdso_info[abi].vdso_pages; i++) - vdso_pagelist[i + 1] = pfn_to_page(pfn + i); + vdso_pagelist[i] = pfn_to_page(pfn + i); - vdso_info[abi].dm->pages = &vdso_pagelist[0]; - vdso_info[abi].cm->pages = &vdso_pagelist[1]; + vdso_info[abi].cm->pages = vdso_pagelist; return 0; } +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; +} + static int __setup_additional_pages(enum vdso_abi abi, struct mm_struct *mm, struct linux_binprm *bprm, @@ -150,7 +154,7 @@ static int __setup_additional_pages(enum vdso_abi abi, } ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE, - VM_READ|VM_MAYREAD, + VM_READ|VM_MAYREAD|VM_PFNMAP, vdso_info[abi].dm); if (IS_ERR(ret)) goto up_fail; @@ -209,6 +213,7 @@ static struct vm_special_mapping aarch32_vdso_maps[] = { #ifdef CONFIG_COMPAT_VDSO [AA32_MAP_VVAR] = { .name = "[vvar]", + .fault = vvar_fault, }, [AA32_MAP_VDSO] = { .name = "[vdso]", @@ -376,6 +381,7 @@ enum aarch64_map { static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = { [AA64_MAP_VVAR] = { .name = "[vvar]", + .fault = vvar_fault, }, [AA64_MAP_VDSO] = { .name = "[vdso]",