Re: [PATCH v6 3/7] mseal, system mappings: enable x86-64

Liam R. Howlett
2025-02-24T21:07:18Z

* jeffxu@chromium.org <jeffxu@chromium.org> [250224 12:45]:
> From: Jeff Xu <jeffxu@chromium.org>
>
> Provide support for CONFIG_MSEAL_SYSTEM_MAPPINGS on x86-64,
> covering the vdso, vvar, vvar_vclock.
>
> Production release testing passes on Android and Chrome OS.
>
> Signed-off-by: Jeff Xu <jeffxu@chromium.org>
> ---
> arch/x86/Kconfig | 1 +
> arch/x86/entry/vdso/vma.c | 16 ++++++++++------
> 2 files changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 87198d957e2f..8fa17032ca46 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -26,6 +26,7 @@ config X86_64
> depends on 64BIT
> # Options that are inherently 64-bit kernel only:
> select ARCH_HAS_GIGANTIC_PAGE
> + select ARCH_HAS_MSEAL_SYSTEM_MAPPINGS
> select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
> select ARCH_SUPPORTS_PER_VMA_LOCK
> select ARCH_SUPPORTS_HUGE_PFNMAP if TRANSPARENT_HUGEPAGE
> diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
> index 39e6efc1a9ca..54677964d0b5 100644
> --- a/arch/x86/entry/vdso/vma.c
> +++ b/arch/x86/entry/vdso/vma.c
> @@ -247,6 +247,7 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
> struct mm_struct *mm = current->mm;
> struct vm_area_struct *vma;
> unsigned long text_start;
> + unsigned long vm_flags;
> int ret = 0;
>
> if (mmap_write_lock_killable(mm))
> @@ -264,11 +265,12 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
> /*
> * MAYWRITE to allow gdb to COW and set breakpoints
> */
> + vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC;
> + vm_flags |= MSEAL_SYSTEM_MAPPINGS_VM_FLAG;
> vma = _install_special_mapping(mm,
> text_start,
> image->size,
> - VM_READ|VM_EXEC|
> - VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
> + vm_flags,

Why not just | VM_SEALED_SYSMAP here, and everywhere else?

> &vdso_mapping);
>
> if (IS_ERR(vma)) {
> @@ -276,11 +278,12 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
> goto up_fail;
> }
>
> + vm_flags = VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|VM_PFNMAP;
> + vm_flags |= MSEAL_SYSTEM_MAPPINGS_VM_FLAG;
> vma = _install_special_mapping(mm,
> addr,
> (__VVAR_PAGES - VDSO_NR_VCLOCK_PAGES) * PAGE_SIZE,
> - VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
> - VM_PFNMAP,
> + vm_flags,
> &vvar_mapping);
>
> if (IS_ERR(vma)) {
> @@ -289,11 +292,12 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
> goto up_fail;
> }
>
> + vm_flags = VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|VM_PFNMAP;
> + vm_flags |= MSEAL_SYSTEM_MAPPINGS_VM_FLAG;
> vma = _install_special_mapping(mm,
> addr + (__VVAR_PAGES - VDSO_NR_VCLOCK_PAGES) * PAGE_SIZE,
> VDSO_NR_VCLOCK_PAGES * PAGE_SIZE,
> - VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
> - VM_PFNMAP,
> + vm_flags,
> &vvar_vclock_mapping);
>
> if (IS_ERR(vma)) {
> --
> 2.48.1.601.g30ceb7b040-goog
>