lguest: extract shadow PTE walking / allocating.
We want a separate find_pte() function so we can call it for populating the switcher PTE entries. We can also use it in page_writable(). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
Родитель
e1d12606f7
Коммит
17427e08fa
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@ -291,6 +291,88 @@ static bool check_gpmd(struct lg_cpu *cpu, pmd_t gpmd)
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}
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#endif
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/*H:331
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* This is the core routine to walk the shadow page tables and find the page
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* table entry for a specific address.
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*
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* If allocate is set, then we allocate any missing levels, setting the flags
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* on the new page directory and mid-level directories using the arguments
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* (which are copied from the Guest's page table entries).
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*/
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static pte_t *find_spte(struct lg_cpu *cpu, unsigned long vaddr, bool allocate,
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int pgd_flags, int pmd_flags)
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{
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pgd_t *spgd;
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/* Mid level for PAE. */
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#ifdef CONFIG_X86_PAE
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pmd_t *spmd;
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#endif
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/* Get top level entry. */
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spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr);
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if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) {
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/* No shadow entry: allocate a new shadow PTE page. */
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unsigned long ptepage;
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/* If they didn't want us to allocate anything, stop. */
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if (!allocate)
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return NULL;
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ptepage = get_zeroed_page(GFP_KERNEL);
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/*
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* This is not really the Guest's fault, but killing it is
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* simple for this corner case.
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*/
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if (!ptepage) {
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kill_guest(cpu, "out of memory allocating pte page");
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return NULL;
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}
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/*
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* And we copy the flags to the shadow PGD entry. The page
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* number in the shadow PGD is the page we just allocated.
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*/
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set_pgd(spgd, __pgd(__pa(ptepage) | pgd_flags));
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}
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/*
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* Intel's Physical Address Extension actually uses three levels of
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* page tables, so we need to look in the mid-level.
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*/
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#ifdef CONFIG_X86_PAE
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/* Now look at the mid-level shadow entry. */
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spmd = spmd_addr(cpu, *spgd, vaddr);
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if (!(pmd_flags(*spmd) & _PAGE_PRESENT)) {
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/* No shadow entry: allocate a new shadow PTE page. */
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unsigned long ptepage;
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/* If they didn't want us to allocate anything, stop. */
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if (!allocate)
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return NULL;
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ptepage = get_zeroed_page(GFP_KERNEL);
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/*
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* This is not really the Guest's fault, but killing it is
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* simple for this corner case.
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*/
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if (!ptepage) {
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kill_guest(cpu, "out of memory allocating pmd page");
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return NULL;
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}
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/*
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* And we copy the flags to the shadow PMD entry. The page
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* number in the shadow PMD is the page we just allocated.
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*/
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set_pmd(spmd, __pmd(__pa(ptepage) | pmd_flags));
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}
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#endif
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/* Get the pointer to the shadow PTE entry we're going to set. */
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return spte_addr(cpu, *spgd, vaddr);
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}
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/*H:330
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* (i) Looking up a page table entry when the Guest faults.
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*
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@ -304,17 +386,11 @@ static bool check_gpmd(struct lg_cpu *cpu, pmd_t gpmd)
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*/
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bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
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{
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pgd_t gpgd;
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pgd_t *spgd;
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unsigned long gpte_ptr;
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pte_t gpte;
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pte_t *spte;
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/* Mid level for PAE. */
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#ifdef CONFIG_X86_PAE
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pmd_t *spmd;
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pmd_t gpmd;
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#endif
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pgd_t gpgd;
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/* We never demand page the Switcher, so trying is a mistake. */
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if (vaddr >= switcher_addr)
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@ -329,67 +405,31 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
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/* Toplevel not present? We can't map it in. */
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if (!(pgd_flags(gpgd) & _PAGE_PRESENT))
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return false;
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}
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/* Now look at the matching shadow entry. */
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spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr);
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if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) {
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/* No shadow entry: allocate a new shadow PTE page. */
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unsigned long ptepage = get_zeroed_page(GFP_KERNEL);
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/*
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* This is not really the Guest's fault, but killing it is
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* simple for this corner case.
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/*
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* This kills the Guest if it has weird flags or tries to
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* refer to a "physical" address outside the bounds.
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*/
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if (!ptepage) {
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kill_guest(cpu, "out of memory allocating pte page");
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return false;
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}
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/* We check that the Guest pgd is OK. */
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if (!check_gpgd(cpu, gpgd))
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return false;
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/*
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* And we copy the flags to the shadow PGD entry. The page
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* number in the shadow PGD is the page we just allocated.
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*/
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set_pgd(spgd, __pgd(__pa(ptepage) | pgd_flags(gpgd)));
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}
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/* This "mid-level" entry is only used for non-linear, PAE mode. */
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gpmd = __pmd(_PAGE_TABLE);
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#ifdef CONFIG_X86_PAE
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if (unlikely(cpu->linear_pages)) {
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/* Faking up a linear mapping. */
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gpmd = __pmd(_PAGE_TABLE);
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} else {
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if (likely(!cpu->linear_pages)) {
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gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);
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/* Middle level not present? We can't map it in. */
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if (!(pmd_flags(gpmd) & _PAGE_PRESENT))
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return false;
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}
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/* Now look at the matching shadow entry. */
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spmd = spmd_addr(cpu, *spgd, vaddr);
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if (!(pmd_flags(*spmd) & _PAGE_PRESENT)) {
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/* No shadow entry: allocate a new shadow PTE page. */
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unsigned long ptepage = get_zeroed_page(GFP_KERNEL);
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/*
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* This is not really the Guest's fault, but killing it is
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* simple for this corner case.
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/*
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* This kills the Guest if it has weird flags or tries to
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* refer to a "physical" address outside the bounds.
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*/
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if (!ptepage) {
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kill_guest(cpu, "out of memory allocating pte page");
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return false;
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}
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/* We check that the Guest pmd is OK. */
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if (!check_gpmd(cpu, gpmd))
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return false;
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/*
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* And we copy the flags to the shadow PMD entry. The page
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* number in the shadow PMD is the page we just allocated.
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*/
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set_pmd(spmd, __pmd(__pa(ptepage) | pmd_flags(gpmd)));
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}
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/*
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@ -441,7 +481,9 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
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gpte = pte_mkdirty(gpte);
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/* Get the pointer to the shadow PTE entry we're going to set. */
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spte = spte_addr(cpu, *spgd, vaddr);
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spte = find_spte(cpu, vaddr, true, pgd_flags(gpgd), pmd_flags(gpmd));
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if (!spte)
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return false;
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/*
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* If there was a valid shadow PTE entry here before, we release it.
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@ -493,33 +535,23 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
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*/
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static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr)
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{
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pgd_t *spgd;
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pte_t *spte;
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unsigned long flags;
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#ifdef CONFIG_X86_PAE
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pmd_t *spmd;
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#endif
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/* You can't put your stack in the Switcher! */
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if (vaddr >= switcher_addr)
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return false;
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/* Look at the current top level entry: is it present? */
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spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr);
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if (!(pgd_flags(*spgd) & _PAGE_PRESENT))
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/* If there's no shadow PTE, it's not writable. */
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spte = find_spte(cpu, vaddr, false, 0, 0);
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if (!spte)
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return false;
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#ifdef CONFIG_X86_PAE
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spmd = spmd_addr(cpu, *spgd, vaddr);
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if (!(pmd_flags(*spmd) & _PAGE_PRESENT))
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return false;
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#endif
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/*
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* Check the flags on the pte entry itself: it must be present and
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* writable.
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*/
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flags = pte_flags(*(spte_addr(cpu, *spgd, vaddr)));
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flags = pte_flags(*spte);
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return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW);
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}
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