Commit-ID: 6baf4bec02dbc41645c3a5130ee15a8e1d62b80f Gitweb: https://git.kernel.org/tip/6baf4bec02dbc41645c3a5130ee15a8e1d62b80f Author: Dave Hansen <[email protected]> AuthorDate: Fri, 6 Apr 2018 13:55:07 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 9 Apr 2018 18:27:33 +0200
x86/espfix: Document use of _PAGE_GLOBAL 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 <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Arjan van de Ven <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Dan Williams <[email protected]> Cc: David Woodhouse <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Juergen Gross <[email protected]> Cc: Kees Cook <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Nadav Amit <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/kernel/espfix_64.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c index e5ec3cafa72e..aebd0d5bc086 100644 --- a/arch/x86/kernel/espfix_64.c +++ b/arch/x86/kernel/espfix_64.c @@ -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);
