84 lines
3.0 KiB
Diff
84 lines
3.0 KiB
Diff
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# Commit cf6d39f81992c29a637c603dbabf1e21a0ea563f
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# Date 2015-09-25 09:05:29 +0200
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# Author Jan Beulich <jbeulich@suse.com>
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# Committer Jan Beulich <jbeulich@suse.com>
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x86/PV: properly populate descriptor tables
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Us extending the GDT limit past the Xen descriptors so far meant that
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guests (including user mode programs) accessing any descriptor table
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slot above the original OS'es limit but below the first Xen descriptor
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caused a #PF, converted to a #GP in our #PF handler. Which is quite
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different from the native behavior, where some of such accesses (LAR
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and LSL) don't fault. Mimic that behavior by mapping a blank page into
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unused slots.
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While not strictly required, treat the LDT the same for consistency.
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Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
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Signed-off-by: Jan Beulich <jbeulich@suse.com>
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Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
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--- a/xen/arch/x86/mm.c
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+++ b/xen/arch/x86/mm.c
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@@ -505,12 +505,13 @@ void update_cr3(struct vcpu *v)
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make_cr3(v, cr3_mfn);
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}
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+static const char __section(".bss.page_aligned") zero_page[PAGE_SIZE];
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static void invalidate_shadow_ldt(struct vcpu *v, int flush)
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{
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l1_pgentry_t *pl1e;
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- int i;
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- unsigned long pfn;
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+ unsigned int i;
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+ unsigned long pfn, zero_pfn = PFN_DOWN(__pa(zero_page));
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struct page_info *page;
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BUG_ON(unlikely(in_irq()));
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@@ -526,8 +527,10 @@ static void invalidate_shadow_ldt(struct
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for ( i = 16; i < 32; i++ )
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{
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pfn = l1e_get_pfn(pl1e[i]);
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- if ( pfn == 0 ) continue;
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- l1e_write(&pl1e[i], l1e_empty());
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+ if ( !(l1e_get_flags(pl1e[i]) & _PAGE_PRESENT) || pfn == zero_pfn )
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+ continue;
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+ l1e_write(&pl1e[i],
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+ l1e_from_pfn(zero_pfn, __PAGE_HYPERVISOR & ~_PAGE_RW));
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page = mfn_to_page(pfn);
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ASSERT_PAGE_IS_TYPE(page, PGT_seg_desc_page);
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ASSERT_PAGE_IS_DOMAIN(page, v->domain);
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@@ -4360,16 +4363,18 @@ long do_update_va_mapping_otherdomain(un
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void destroy_gdt(struct vcpu *v)
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{
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l1_pgentry_t *pl1e;
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- int i;
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- unsigned long pfn;
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+ unsigned int i;
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+ unsigned long pfn, zero_pfn = PFN_DOWN(__pa(zero_page));
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v->arch.pv_vcpu.gdt_ents = 0;
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pl1e = gdt_ldt_ptes(v->domain, v);
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for ( i = 0; i < FIRST_RESERVED_GDT_PAGE; i++ )
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{
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- if ( (pfn = l1e_get_pfn(pl1e[i])) != 0 )
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+ pfn = l1e_get_pfn(pl1e[i]);
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+ if ( (l1e_get_flags(pl1e[i]) & _PAGE_PRESENT) && pfn != zero_pfn )
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put_page_and_type(mfn_to_page(pfn));
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- l1e_write(&pl1e[i], l1e_empty());
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+ l1e_write(&pl1e[i],
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+ l1e_from_pfn(zero_pfn, __PAGE_HYPERVISOR & ~_PAGE_RW));
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v->arch.pv_vcpu.gdt_frames[i] = 0;
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}
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}
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@@ -4382,7 +4387,7 @@ long set_gdt(struct vcpu *v,
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struct domain *d = v->domain;
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l1_pgentry_t *pl1e;
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/* NB. There are 512 8-byte entries per GDT page. */
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- int i, nr_pages = (entries + 511) / 512;
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+ unsigned int i, nr_pages = (entries + 511) / 512;
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if ( entries > FIRST_RESERVED_GDT_ENTRY )
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return -EINVAL;
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