diff options
| -rw-r--r-- | drivers/lguest/lg.h | 1 | ||||
| -rw-r--r-- | drivers/lguest/page_tables.c | 42 |
2 files changed, 33 insertions, 10 deletions
diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h index faac9fc..005929a 100644 --- a/drivers/lguest/lg.h +++ b/drivers/lguest/lg.h @@ -16,6 +16,7 @@ struct pgdir { unsigned long gpgdir; + bool switcher_mapped; pgd_t *pgdir; }; diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index 1f48f27..d1a5de4 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -736,18 +736,39 @@ static unsigned int new_pgdir(struct lg_cpu *cpu, /*H:501 * We do need the Switcher code mapped at all times, so we allocate that - * part of the Guest page table here, and populate it when we're about to run - * the guest. + * part of the Guest page table here. We map the Switcher code immediately, + * but defer mapping of the guest register page and IDT/LDT etc page until + * just before we run the guest in map_switcher_in_guest(). + * + * We *could* do this setup in map_switcher_in_guest(), but at that point + * we've interrupts disabled, and allocating pages like that is fraught: we + * can't sleep if we need to free up some memory. */ static bool allocate_switcher_mapping(struct lg_cpu *cpu) { int i; for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) { - if (!find_spte(cpu, switcher_addr + i * PAGE_SIZE, true, - CHECK_GPGD_MASK, _PAGE_TABLE)) + pte_t *pte = find_spte(cpu, switcher_addr + i * PAGE_SIZE, true, + CHECK_GPGD_MASK, _PAGE_TABLE); + if (!pte) return false; + + /* + * Map the switcher page if not already there. It might + * already be there because we call allocate_switcher_mapping() + * in guest_set_pgd() just in case it did discard our Switcher + * mapping, but it probably didn't. + */ + if (i == 0 && !(pte_flags(*pte) & _PAGE_PRESENT)) { + /* Get a reference to the Switcher page. */ + get_page(lg_switcher_pages[0]); + /* Create a read-only, exectuable, kernel-style PTE */ + set_pte(pte, + mk_pte(lg_switcher_pages[0], PAGE_KERNEL_RX)); + } } + cpu->lg->pgdirs[cpu->cpu_pgd].switcher_mapped = true; return true; } @@ -768,6 +789,7 @@ static void release_all_pagetables(struct lguest *lg) /* Every PGD entry. */ for (j = 0; j < PTRS_PER_PGD; j++) release_pgd(lg->pgdirs[i].pgdir + j); + lg->pgdirs[i].switcher_mapped = false; } } @@ -827,8 +849,10 @@ void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable) if (repin) pin_stack_pages(cpu); - if (!allocate_switcher_mapping(cpu)) - kill_guest(cpu, "Cannot populate switcher mapping"); + if (!cpu->lg->pgdirs[cpu->cpu_pgd].switcher_mapped) { + if (!allocate_switcher_mapping(cpu)) + kill_guest(cpu, "Cannot populate switcher mapping"); + } } /*:*/ @@ -1076,10 +1100,8 @@ void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages) struct page *percpu_switcher_page, *regs_page; pte_t *pte; - /* Code page should always be mapped, and executable. */ - pte = find_spte(cpu, switcher_addr, false, 0, 0); - get_page(lg_switcher_pages[0]); - set_pte(pte, mk_pte(lg_switcher_pages[0], PAGE_KERNEL_RX)); + /* Switcher page should always be mapped! */ + BUG_ON(!cpu->lg->pgdirs[cpu->cpu_pgd].switcher_mapped); /* Clear all the Switcher mappings for any other CPUs. */ /* FIXME: This is dumb: update only when Host CPU changes. */ |
