Messages in this thread Patch in this message |  | | Subject | [PATCH 04/11] x86/espfix: document use of _PAGE_GLOBAL | From | Dave Hansen <> | Date | Fri, 06 Apr 2018 13:55:07 -0700 |
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From: Dave Hansen <dave.hansen@linux.intel.com>
The "normal" kernel page table creation mechanisms using PAGE_KERNEL_* page protections will never set _PAGE_GLOBAL with PTI. The few places in the kernel that always want _PAGE_GLOBAL must avoid using PAGE_KERNEL_*.
Document that we want it here and its use is not accidental.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Kees Cook <keescook@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Juergen Gross <jgross@suse.com> Cc: x86@kernel.org Cc: Nadav Amit <namit@vmware.com> ---
b/arch/x86/kernel/espfix_64.c | 4 ++++ 1 file changed, 4 insertions(+)
diff -puN arch/x86/kernel/espfix_64.c~espfix-use-kern-defaults-not-supported arch/x86/kernel/espfix_64.c --- a/arch/x86/kernel/espfix_64.c~espfix-use-kern-defaults-not-supported 2018-04-06 10:47:55.343796126 -0700 +++ b/arch/x86/kernel/espfix_64.c 2018-04-06 10:47:55.346796126 -0700 @@ -195,6 +195,10 @@ void init_espfix_ap(int cpu) pte_p = pte_offset_kernel(&pmd, addr); stack_page = page_address(alloc_pages_node(node, GFP_KERNEL, 0)); + /* + * __PAGE_KERNEL_* includes _PAGE_GLOBAL, which we want since + * this is mapped to userspace. + */ pte = __pte(__pa(stack_page) | ((__PAGE_KERNEL_RO | _PAGE_ENC) & ptemask)); for (n = 0; n < ESPFIX_PTE_CLONES; n++) set_pte(&pte_p[n*PTE_STRIDE], pte); _
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