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Commit c9e433e4 authored by Rusty Russell's avatar Rusty Russell
Browse files

lguest: add infrastructure to check mappings. 



We normally abort the guest unconditionally when it gives us a bad address,
but in the next patch we want to copy some bytes which may not be mapped.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 8ed31300

drivers/lguest/lg.h

+1 −0
Original line number Diff line number Diff line
@@ -202,6 +202,7 @@ void guest_set_pte(struct lg_cpu *cpu, unsigned long gpgdir, 
void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages);

bool demand_page(struct lg_cpu *cpu, unsigned long cr2, int errcode);

void pin_page(struct lg_cpu *cpu, unsigned long vaddr);

bool __guest_pa(struct lg_cpu *cpu, unsigned long vaddr, unsigned long *paddr);

unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr);

void page_table_guest_data_init(struct lg_cpu *cpu);

drivers/lguest/page_tables.c

+29 −13
Original line number Diff line number Diff line
@@ -647,7 +647,7 @@ void guest_pagetable_flush_user(struct lg_cpu *cpu) 
/*:*/



/* We walk down the guest page tables to get a guest-physical address */

unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr)

bool __guest_pa(struct lg_cpu *cpu, unsigned long vaddr, unsigned long *paddr)

{

	pgd_t gpgd;

	pte_t gpte;
@@ -656,31 +656,47 @@ unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr) 
#endif



	/* Still not set up?  Just map 1:1. */

	if (unlikely(cpu->linear_pages))

		return vaddr;

	if (unlikely(cpu->linear_pages)) {

		*paddr = vaddr;

		return true;

	}



	/* First step: get the top-level Guest page table entry. */

	gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t);

	/* Toplevel not present?  We can't map it in. */

	if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) {

		kill_guest(cpu, "Bad address %#lx", vaddr);

		return -1UL;

	}

	if (!(pgd_flags(gpgd) & _PAGE_PRESENT))

		goto fail;



#ifdef CONFIG_X86_PAE

	gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);

	if (!(pmd_flags(gpmd) & _PAGE_PRESENT)) {

		kill_guest(cpu, "Bad address %#lx", vaddr);

		return -1UL;

	}

	if (!(pmd_flags(gpmd) & _PAGE_PRESENT))

		goto fail;

	gpte = lgread(cpu, gpte_addr(cpu, gpmd, vaddr), pte_t);

#else

	gpte = lgread(cpu, gpte_addr(cpu, gpgd, vaddr), pte_t);

#endif

	if (!(pte_flags(gpte) & _PAGE_PRESENT))

		kill_guest(cpu, "Bad address %#lx", vaddr);

		goto fail;



	*paddr = pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK);

	return true;



fail:

	*paddr = -1UL;

	return false;

}



	return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK);

/*

 * This is the version we normally use: kills the Guest if it uses a

 * bad address

 */

unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr)

{

	unsigned long paddr;



	if (!__guest_pa(cpu, vaddr, &paddr))

		kill_guest(cpu, "Bad address %#lx", vaddr);

	return paddr;

}



/*