From 47436aa4ad054c1c7c8231618e86ebd9305308dc Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Mon, 22 Oct 2007 11:03:36 +1000 Subject: Boot with virtual == physical to get closer to native Linux. 1) This allows us to get alot closer to booting bzImages. 2) It means we don't have to know page_offset. 3) The Guest needs to modify the boot pagetables to create the PAGE_OFFSET mapping before jumping to C code. 4) guest_pa() walks the page tables rather than using page_offset. 5) We don't use page_offset to figure out whether to emulate: it was always kinda quesationable, and won't work for instructions done before remapping (bzImage unpacking in particular). 6) We still want the kernel address for tlb flushing: have the initial hypercall give us that, too. Signed-off-by: Rusty Russell --- drivers/lguest/page_tables.c | 47 +++++++++++++++++++++++++++++++++++++------- 1 file changed, 40 insertions(+), 7 deletions(-) (limited to 'drivers/lguest/page_tables.c') diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index bfe3650b28d..fe3c7575647 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -13,6 +13,7 @@ #include #include #include +#include #include "lg.h" /*M:008 We hold reference to pages, which prevents them from being swapped. @@ -345,7 +346,7 @@ static void flush_user_mappings(struct lguest *lg, int idx) { unsigned int i; /* Release every pgd entry up to the kernel's address. */ - for (i = 0; i < pgd_index(lg->page_offset); i++) + for (i = 0; i < pgd_index(lg->kernel_address); i++) release_pgd(lg, lg->pgdirs[idx].pgdir + i); } @@ -358,6 +359,25 @@ void guest_pagetable_flush_user(struct lguest *lg) } /*:*/ +/* We walk down the guest page tables to get a guest-physical address */ +unsigned long guest_pa(struct lguest *lg, unsigned long vaddr) +{ + pgd_t gpgd; + pte_t gpte; + + /* First step: get the top-level Guest page table entry. */ + gpgd = __pgd(lgread_u32(lg, gpgd_addr(lg, vaddr))); + /* Toplevel not present? We can't map it in. */ + if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) + kill_guest(lg, "Bad address %#lx", vaddr); + + gpte = __pte(lgread_u32(lg, gpte_addr(lg, gpgd, vaddr))); + if (!(pte_flags(gpte) & _PAGE_PRESENT)) + kill_guest(lg, "Bad address %#lx", vaddr); + + return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK); +} + /* We keep several page tables. This is a simple routine to find the page * table (if any) corresponding to this top-level address the Guest has given * us. */ @@ -500,7 +520,7 @@ void guest_set_pte(struct lguest *lg, { /* Kernel mappings must be changed on all top levels. Slow, but * doesn't happen often. */ - if (vaddr >= lg->page_offset) { + if (vaddr >= lg->kernel_address) { unsigned int i; for (i = 0; i < ARRAY_SIZE(lg->pgdirs); i++) if (lg->pgdirs[i].pgdir) @@ -550,11 +570,6 @@ void guest_set_pmd(struct lguest *lg, unsigned long gpgdir, u32 idx) * its first page table is. We set some things up here: */ int init_guest_pagetable(struct lguest *lg, unsigned long pgtable) { - /* In flush_user_mappings() we loop from 0 to - * "pgd_index(lg->page_offset)". This assumes it won't hit - * the Switcher mappings, so check that now. */ - if (pgd_index(lg->page_offset) >= SWITCHER_PGD_INDEX) - return -EINVAL; /* We start on the first shadow page table, and give it a blank PGD * page. */ lg->pgdidx = 0; @@ -565,6 +580,24 @@ int init_guest_pagetable(struct lguest *lg, unsigned long pgtable) return 0; } +/* When the Guest calls LHCALL_LGUEST_INIT we do more setup. */ +void page_table_guest_data_init(struct lguest *lg) +{ + /* We get the kernel address: above this is all kernel memory. */ + if (get_user(lg->kernel_address, &lg->lguest_data->kernel_address) + /* We tell the Guest that it can't use the top 4MB of virtual + * addresses used by the Switcher. */ + || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem) + || put_user(lg->pgdirs[lg->pgdidx].gpgdir,&lg->lguest_data->pgdir)) + kill_guest(lg, "bad guest page %p", lg->lguest_data); + + /* In flush_user_mappings() we loop from 0 to + * "pgd_index(lg->kernel_address)". This assumes it won't hit the + * Switcher mappings, so check that now. */ + if (pgd_index(lg->kernel_address) >= SWITCHER_PGD_INDEX) + kill_guest(lg, "bad kernel address %#lx", lg->kernel_address); +} + /* When a Guest dies, our cleanup is fairly simple. */ void free_guest_pagetable(struct lguest *lg) { -- cgit v1.2.3