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VM: fix corruption from recursive PDE allocation

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Change-Id: I6176b849fefca4bed3e92648b0d72ff47658915c
This commit is contained in:
David van Moolenbroek 2014-02-25 15:04:02 +01:00 committed by Lionel Sambuc
parent 415782f70f
commit f199fc0bfe
1 changed files with 12 additions and 2 deletions
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14
servers/vm/pagetable.c
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@ -487,6 +487,7 @@ static int pt_ptalloc(pt_t *pt, int pde, u32_t flags)
/* Allocate a page table and write its address into the page directory. */
int i;
phys_bytes pt_phys;
u32_t *p;
/* Argument must make sense. */
assert(pde >= 0 && pde < ARCH_VM_DIR_ENTRIES);
@ -498,9 +499,18 @@ static int pt_ptalloc(pt_t *pt, int pde, u32_t flags)
assert(!(pt->pt_dir[pde] & ARCH_VM_PDE_PRESENT));
assert(!pt->pt_pt[pde]);
/* Get storage for the page table. */
if(!(pt->pt_pt[pde] = vm_allocpage(&pt_phys, VMP_PAGETABLE)))
/* Get storage for the page table. The allocation call may in fact
* recursively create the directory entry as a side effect. In that
* case, we free the newly allocated page and do nothing else.
*/
if (!(p = vm_allocpage(&pt_phys, VMP_PAGETABLE)))
return ENOMEM;
if (pt->pt_pt[pde]) {
vm_freepages((vir_bytes) p, 1);
assert(pt->pt_pt[pde]);
return OK;
}
pt->pt_pt[pde] = p;
for(i = 0; i < ARCH_VM_PT_ENTRIES; i++)
pt->pt_pt[pde][i] = 0; /* Empty entry. */