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Assert that the size in mappages() is always positive

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If va % PGSIZE == 0 and size == 0, we have last < a at the start of
the loop so we might never terminate.  That being said, this
particular case couldn't be triggered for now.
This commit is contained in:
l0stman 2020-11-10 08:31:16 +03:00 committed by Frans Kaashoek
parent f55def8a64
commit 9195142959
1 changed files with 4 additions and 1 deletions
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5
kernel/vm.c
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@ -140,13 +140,16 @@ mappages(pagetable_t pagetable, uint64 va, uint64 size, uint64 pa, int perm)
uint64 a, last; uint64 a, last;
pte_t *pte; pte_t *pte;
if(size == 0)
panic("mappages: size");
a = PGROUNDDOWN(va); a = PGROUNDDOWN(va);
last = PGROUNDDOWN(va + size - 1); last = PGROUNDDOWN(va + size - 1);
for(;;){ for(;;){
if((pte = walk(pagetable, a, 1)) == 0) if((pte = walk(pagetable, a, 1)) == 0)
return -1; return -1;
if(*pte & PTE_V) if(*pte & PTE_V)
panic("remap"); panic("mappages: remap");
*pte = PA2PTE(pa) | perm | PTE_V; *pte = PA2PTE(pa) | perm | PTE_V;
if(a == last) if(a == last)
break; break;