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authorRusty Russell <rusty@rustcorp.com.au>2013-04-22 14:10:39 +0930
committerRusty Russell <rusty@rustcorp.com.au>2013-04-22 15:31:39 +0930
commite1d12606f756bdb8328a66a2873dca6c46bcb4e5 (patch)
tree25464220a1fe74504cd5a8d0801913594e25539d
parent93a2cdff98243df06bafd3c4f3b31b38f0d0fe3e (diff)
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>
-rw-r--r--drivers/lguest/page_tables.c33
1 files changed, 23 insertions, 10 deletions
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
index 758466299b0d..f074f34acb86 100644
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -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));