| Date | Mon, 04 Dec 2017 15:07:41 +0100 | From | Thomas Gleixner <> | Subject | [patch 35/60] x86/espfix: Ensure that ESPFIX is visible in user PGD |
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From: Dave Hansen <dave.hansen@linux.intel.com>
Clone the ESPFIX alias mapping area so the entry/exit code has access to it even with the user space page tables.
[ tglx: Remove the per cpu user mapped oddity ]
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
--- arch/x86/kernel/espfix_64.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
--- a/arch/x86/kernel/espfix_64.c +++ b/arch/x86/kernel/espfix_64.c @@ -129,6 +129,22 @@ void __init init_espfix_bsp(void) p4d = p4d_alloc(&init_mm, pgd, ESPFIX_BASE_ADDR); p4d_populate(&init_mm, p4d, espfix_pud_page); + /* + * Just copy the top-level PGD that is mapping the espfix area to + * ensure it is mapped into the user page tables. + * + * For 5-level paging, the espfix pgd was populated when + * kpti_init() pre-populated all the pgd entries. The above + * p4d_alloc() would never do anything and the p4d_populate() would + * be done to a p4d already mapped in the userspace pgd. + */ +#ifdef CONFIG_KERNEL_PAGE_TABLE_ISOLATION + if (CONFIG_PGTABLE_LEVELS <= 4) { + set_pgd(kernel_to_user_pgdp(pgd), + __pgd(_KERNPG_TABLE | (p4d_pfn(*p4d) << PAGE_SHIFT))); + } +#endif + /* Randomize the locations */ init_espfix_random();
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