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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: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2015-02-11 15:15:09 +10:30
parent 8ed313001a
commit c9e433e4b8
2 changed files with 30 additions and 13 deletions
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1
drivers/lguest/lg.h
View File

@ -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);

42
drivers/lguest/page_tables.c
View File

@ -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;
return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK);
*paddr = pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK);
return true;
fail:
*paddr = -1UL;
return false;
}
/*
* 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;
}
/*