From: Arjan van de Ven Date: Fri, 6 Jan 2006 08:12:03 +0000 (-0800) Subject: [PATCH] x86/x86_64: mark rodata section read only: generic x86-64 bugfix X-Git-Tag: v2.6.16-rc1~936^2~194 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c728252c7a072628bd3932ff87943d1e12423359;p=linux-2.6 [PATCH] x86/x86_64: mark rodata section read only: generic x86-64 bugfix Bug fix required for the .rodata work on x86-64: when change_page_attr() and friends need to break up a 2Mb page into 4Kb pages, it always set the NX bit on the PMD, which causes the cpu to consider the entire 2Mb region to be NX regardless of the actual PTE perms. This is fine in general, with one big exception: the 2Mb page that covers the last part of the kernel .text! The fix is to not invent a new permission for the new PMD entry, but to just inherit the existing one minus the PSE bit. Signed-off-by: Arjan van de Ven Signed-off-by: Ingo Molnar Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/x86_64/mm/pageattr.c b/arch/x86_64/mm/pageattr.c index b90e8fe9ee..35f1f1aab0 100644 --- a/arch/x86_64/mm/pageattr.c +++ b/arch/x86_64/mm/pageattr.c @@ -128,6 +128,7 @@ __change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot, pte_t *kpte; struct page *kpte_page; unsigned kpte_flags; + pgprot_t ref_prot2; kpte = lookup_address(address); if (!kpte) return 0; kpte_page = virt_to_page(((unsigned long)kpte) & PAGE_MASK); @@ -140,10 +141,14 @@ __change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot, * split_large_page will take the reference for this change_page_attr * on the split page. */ - struct page *split = split_large_page(address, prot, ref_prot); + + struct page *split; + ref_prot2 = __pgprot(pgprot_val(pte_pgprot(*lookup_address(address))) & ~(1<<_PAGE_BIT_PSE)); + + split = split_large_page(address, prot, ref_prot2); if (!split) return -ENOMEM; - set_pte(kpte,mk_pte(split, ref_prot)); + set_pte(kpte,mk_pte(split, ref_prot2)); kpte_page = split; } get_page(kpte_page); diff --git a/include/asm-x86_64/pgtable.h b/include/asm-x86_64/pgtable.h index ecf58c7c16..02888d7a49 100644 --- a/include/asm-x86_64/pgtable.h +++ b/include/asm-x86_64/pgtable.h @@ -122,6 +122,8 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm, unsigned long #define pte_same(a, b) ((a).pte == (b).pte) +#define pte_pgprot(a) (__pgprot((a).pte & ~PHYSICAL_PAGE_MASK)) + #define PMD_SIZE (1UL << PMD_SHIFT) #define PMD_MASK (~(PMD_SIZE-1)) #define PUD_SIZE (1UL << PUD_SHIFT)