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author | Robert Morris <[email protected]> | 2019-07-02 11:45:06 -0400 |
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committer | Robert Morris <[email protected]> | 2019-07-02 11:45:06 -0400 |
commit | f59c1bf1d82da4b445c1cff10c228ea55fa035d4 (patch) | |
tree | 894695263c3509c2923d59ee6ba77857134701dc /kernel/vm.c | |
parent | b27f275014cb473960b9e4d36b03455e404116a7 (diff) | |
download | xv6-labs-f59c1bf1d82da4b445c1cff10c228ea55fa035d4.tar.gz xv6-labs-f59c1bf1d82da4b445c1cff10c228ea55fa035d4.tar.bz2 xv6-labs-f59c1bf1d82da4b445c1cff10c228ea55fa035d4.zip |
try to continue from walk() failing to allocate a page-table page
Diffstat (limited to 'kernel/vm.c')
-rw-r--r-- | kernel/vm.c | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/kernel/vm.c b/kernel/vm.c index d5ff594..bdb53c2 100644 --- a/kernel/vm.c +++ b/kernel/vm.c @@ -119,8 +119,9 @@ walkaddr(pagetable_t pagetable, uint64 va) // Create PTEs for virtual addresses starting at va that refer to // physical addresses starting at pa. va and size might not -// be page-aligned. -void +// be page-aligned. Returns 0 on success, -1 if walk() couldn't +// allocate a needed page-table page. +int mappages(pagetable_t pagetable, uint64 va, uint64 size, uint64 pa, int perm) { uint64 a, last; @@ -130,7 +131,7 @@ mappages(pagetable_t pagetable, uint64 va, uint64 size, uint64 pa, int perm) last = PGROUNDDOWN(va + size - 1); for(;;){ if((pte = walk(pagetable, a, 1)) == 0) - panic("mappages: walk"); + return -1; if(*pte & PTE_V) panic("remap"); *pte = PA2PTE(pa) | perm | PTE_V; @@ -139,6 +140,7 @@ mappages(pagetable_t pagetable, uint64 va, uint64 size, uint64 pa, int perm) a += PGSIZE; pa += PGSIZE; } + return 0; } // Remove mappings from a page table. The mappings in @@ -222,7 +224,11 @@ uvmalloc(pagetable_t pagetable, uint64 oldsz, uint64 newsz) return 0; } memset(mem, 0, PGSIZE); - mappages(pagetable, a, PGSIZE, (uint64)mem, PTE_W|PTE_X|PTE_R|PTE_U); + if(mappages(pagetable, a, PGSIZE, (uint64)mem, PTE_W|PTE_X|PTE_R|PTE_U) != 0){ + kfree(mem); + uvmdealloc(pagetable, a, oldsz); + return 0; + } } return newsz; } @@ -293,7 +299,10 @@ uvmcopy(pagetable_t old, pagetable_t new, uint64 sz) if((mem = kalloc()) == 0) goto err; memmove(mem, (char*)pa, PGSIZE); - mappages(new, i, PGSIZE, (uint64)mem, flags); + if(mappages(new, i, PGSIZE, (uint64)mem, flags) != 0){ + kfree(mem); + goto err; + } } return 0; |