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| author | Jeremy Fitzhardinge <jeremy@xensource.com> | 2007-07-17 18:37:05 -0700 |
|---|---|---|
| committer | Jeremy Fitzhardinge <jeremy@goop.org> | 2007-07-18 08:47:43 -0700 |
| commit | 9a4029fd3409eb224eb62c32d9792071382694ec (patch) | |
| tree | 04a8f54abadf6a3c8afff3281b120108c4e33d45 /arch | |
| parent | f4f97b3ea90130520afb478cbc2918be2b6587b8 (diff) | |
| download | lwn-9a4029fd3409eb224eb62c32d9792071382694ec.tar.gz lwn-9a4029fd3409eb224eb62c32d9792071382694ec.zip | |
xen: ignore RW mapping of RO pages in pagetable_init
When setting up the initial pagetable, which includes mappings of all
low physical memory, ignore a mapping which tries to set the RW bit on
an RO pte. An RO pte indicates a page which is part of the current
pagetable, and so it cannot be allowed to become RW.
Once xen_pagetable_setup_done is called, set_pte reverts to its normal
behaviour.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Acked-by: Chris Wright <chrisw@sous-sol.org>
Cc: ebiederm@xmission.com (Eric W. Biederman)
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/i386/xen/enlighten.c | 27 |
1 files changed, 25 insertions, 2 deletions
diff --git a/arch/i386/xen/enlighten.c b/arch/i386/xen/enlighten.c index 86e68e680116..9550ae3b1fb1 100644 --- a/arch/i386/xen/enlighten.c +++ b/arch/i386/xen/enlighten.c @@ -505,7 +505,7 @@ static void xen_write_cr3(unsigned long cr3) /* Early in boot, while setting up the initial pagetable, assume everything is pinned. */ -static void xen_alloc_pt_init(struct mm_struct *mm, u32 pfn) +static __init void xen_alloc_pt_init(struct mm_struct *mm, u32 pfn) { BUG_ON(mem_map); /* should only be used early */ make_lowmem_page_readonly(__va(PFN_PHYS(pfn))); @@ -557,10 +557,32 @@ static void *xen_kmap_atomic_pte(struct page *page, enum km_type type) } #endif +static __init pte_t mask_rw_pte(pte_t *ptep, pte_t pte) +{ + /* If there's an existing pte, then don't allow _PAGE_RW to be set */ + if (pte_val_ma(*ptep) & _PAGE_PRESENT) + pte = __pte_ma(((pte_val_ma(*ptep) & _PAGE_RW) | ~_PAGE_RW) & + pte_val_ma(pte)); + + return pte; +} + +/* Init-time set_pte while constructing initial pagetables, which + doesn't allow RO pagetable pages to be remapped RW */ +static __init void xen_set_pte_init(pte_t *ptep, pte_t pte) +{ + pte = mask_rw_pte(ptep, pte); + + xen_set_pte(ptep, pte); +} + static __init void xen_pagetable_setup_start(pgd_t *base) { pgd_t *xen_pgd = (pgd_t *)xen_start_info->pt_base; + /* special set_pte for pagetable initialization */ + paravirt_ops.set_pte = xen_set_pte_init; + init_mm.pgd = base; /* * copy top-level of Xen-supplied pagetable into place. For @@ -607,6 +629,7 @@ static __init void xen_pagetable_setup_done(pgd_t *base) /* This will work as long as patching hasn't happened yet (which it hasn't) */ paravirt_ops.alloc_pt = xen_alloc_pt; + paravirt_ops.set_pte = xen_set_pte; if (!xen_feature(XENFEAT_auto_translated_physmap)) { /* @@ -745,7 +768,7 @@ static const struct paravirt_ops xen_paravirt_ops __initdata = { .kmap_atomic_pte = xen_kmap_atomic_pte, #endif - .set_pte = xen_set_pte, + .set_pte = NULL, /* see xen_pagetable_setup_* */ .set_pte_at = xen_set_pte_at, .set_pmd = xen_set_pmd, |