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lguest: make check_gpte et. al return bool. 

This is a bit neater: we can immediately return if a PTE/PGD/PMD entry
is invalid (which also kills the guest).  It means we don't risk using
invalid entries as we reshuffle the code.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2013-04-22 14:10:39 +09:30
parent 93a2cdff98
commit e1d12606f7
1 changed files with 23 additions and 10 deletions
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33
drivers/lguest/page_tables.c
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@ -259,26 +259,35 @@ static void release_pte(pte_t pte)
}
/*:*/
static void check_gpte(struct lg_cpu *cpu, pte_t gpte)
static bool check_gpte(struct lg_cpu *cpu, pte_t gpte)
{
if ((pte_flags(gpte) & _PAGE_PSE) ||
pte_pfn(gpte) >= cpu->lg->pfn_limit)
pte_pfn(gpte) >= cpu->lg->pfn_limit) {
kill_guest(cpu, "bad page table entry");
return false;
}
return true;
}
static void check_gpgd(struct lg_cpu *cpu, pgd_t gpgd)
static bool check_gpgd(struct lg_cpu *cpu, pgd_t gpgd)
{
if ((pgd_flags(gpgd) & ~CHECK_GPGD_MASK) ||
(pgd_pfn(gpgd) >= cpu->lg->pfn_limit))
(pgd_pfn(gpgd) >= cpu->lg->pfn_limit)) {
kill_guest(cpu, "bad page directory entry");
return false;
}
return true;
}
#ifdef CONFIG_X86_PAE
static void check_gpmd(struct lg_cpu *cpu, pmd_t gpmd)
static bool check_gpmd(struct lg_cpu *cpu, pmd_t gpmd)
{
if ((pmd_flags(gpmd) & ~_PAGE_TABLE) ||
(pmd_pfn(gpmd) >= cpu->lg->pfn_limit))
(pmd_pfn(gpmd) >= cpu->lg->pfn_limit)) {
kill_guest(cpu, "bad page middle directory entry");
return false;
}
return true;
}
#endif
@ -336,7 +345,8 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
return false;
}
/* We check that the Guest pgd is OK. */
check_gpgd(cpu, gpgd);
if (!check_gpgd(cpu, gpgd))
return false;
/*
* And we copy the flags to the shadow PGD entry. The page
* number in the shadow PGD is the page we just allocated.
@ -372,7 +382,8 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
}
/* We check that the Guest pmd is OK. */
check_gpmd(cpu, gpmd);
if (!check_gpmd(cpu, gpmd))
return false;
/*
* And we copy the flags to the shadow PMD entry. The page
@ -421,7 +432,8 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
* Check that the Guest PTE flags are OK, and the page number is below
* the pfn_limit (ie. not mapping the Launcher binary).
*/
check_gpte(cpu, gpte);
if (!check_gpte(cpu, gpte))
return false;
/* Add the _PAGE_ACCESSED and (for a write) _PAGE_DIRTY flag */
gpte = pte_mkyoung(gpte);
@ -857,7 +869,8 @@ static void do_set_pte(struct lg_cpu *cpu, int idx,
* micro-benchmark.
*/
if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) {
check_gpte(cpu, gpte);
if (!check_gpte(cpu, gpte))
return;
set_pte(spte,
gpte_to_spte(cpu, gpte,
pte_flags(gpte) & _PAGE_DIRTY));