forked from luck/tmp_suning_uos_patched
Revert "x86/mm/legacy: Populate the user page-table with user pgd's"
This reverts commit1f40a46cf4
. It turned out that this patch is not sufficient to enable PTI on 32 bit systems with legacy 2-level page-tables. In this paging mode the huge-page PTEs are in the top-level page-table directory, where also the mirroring to the user-space page-table happens. So every huge PTE exits twice, in the kernel and in the user page-table. That means that accessed/dirty bits need to be fetched from two PTEs in this mode to be safe, but this is not trivial to implement because it needs changes to generic code just for the sake of enabling PTI with 32-bit legacy paging. As all systems that need PTI should support PAE anyway, remove support for PTI when 32-bit legacy paging is used. Fixes:7757d607c6
('x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32') Reported-by: Meelis Roos <mroos@linux.ee> Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: hpa@zytor.com Cc: linux-mm@kvack.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Andrea Arcangeli <aarcange@redhat.com> Link: https://lkml.kernel.org/r/1536922754-31379-1-git-send-email-joro@8bytes.org
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cf40361ede
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61a6bd83ab
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@ -19,9 +19,6 @@ static inline void native_set_pte(pte_t *ptep , pte_t pte)
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static inline void native_set_pmd(pmd_t *pmdp, pmd_t pmd)
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{
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#ifdef CONFIG_PAGE_TABLE_ISOLATION
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pmd.pud.p4d.pgd = pti_set_user_pgtbl(&pmdp->pud.p4d.pgd, pmd.pud.p4d.pgd);
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#endif
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*pmdp = pmd;
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}
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@ -61,9 +58,6 @@ static inline pte_t native_ptep_get_and_clear(pte_t *xp)
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#ifdef CONFIG_SMP
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static inline pmd_t native_pmdp_get_and_clear(pmd_t *xp)
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{
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#ifdef CONFIG_PAGE_TABLE_ISOLATION
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pti_set_user_pgtbl(&xp->pud.p4d.pgd, __pgd(0));
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#endif
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return __pmd(xchg((pmdval_t *)xp, 0));
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}
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#else
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@ -73,9 +67,6 @@ static inline pmd_t native_pmdp_get_and_clear(pmd_t *xp)
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#ifdef CONFIG_SMP
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static inline pud_t native_pudp_get_and_clear(pud_t *xp)
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{
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#ifdef CONFIG_PAGE_TABLE_ISOLATION
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pti_set_user_pgtbl(&xp->p4d.pgd, __pgd(0));
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#endif
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return __pud(xchg((pudval_t *)xp, 0));
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}
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#else
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@ -57,7 +57,7 @@ config SECURITY_NETWORK
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config PAGE_TABLE_ISOLATION
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bool "Remove the kernel mapping in user mode"
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default y
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depends on X86 && !UML
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depends on (X86_64 || X86_PAE) && !UML
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help
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This feature reduces the number of hardware side channels by
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ensuring that the majority of kernel addresses are not mapped
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