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| author | Robert Morris <rtm@csail.mit.edu> | 2019-07-02 11:45:06 -0400 |
|---|---|---|
| committer | Robert Morris <rtm@csail.mit.edu> | 2019-07-02 11:45:06 -0400 |
| commit | f59c1bf1d82da4b445c1cff10c228ea55fa035d4 (patch) | |
| tree | 894695263c3509c2923d59ee6ba77857134701dc | |
| 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
| -rw-r--r-- | kernel/defs.h | 4 | ||||
| -rw-r--r-- | kernel/vm.c | 19 | ||||
| -rw-r--r-- | user/usertests.c | 2 |
3 files changed, 17 insertions, 8 deletions
diff --git a/kernel/defs.h b/kernel/defs.h index 1c0b39a..bd89af0 100644 --- a/kernel/defs.h +++ b/kernel/defs.h @@ -185,9 +185,9 @@ pagetable_t uvmcreate(void); void uvminit(pagetable_t, uchar *, uint); uint64 uvmalloc(pagetable_t, uint64, uint64); uint64 uvmdealloc(pagetable_t, uint64, uint64); -int uvmcopy(pagetable_t, pagetable_t, uint64); +int uvmcopy(pagetable_t, pagetable_t, uint64); void uvmfree(pagetable_t, uint64); -void mappages(pagetable_t, uint64, uint64, uint64, int); +int mappages(pagetable_t, uint64, uint64, uint64, int); void unmappages(pagetable_t, uint64, uint64, int); uint64 walkaddr(pagetable_t, uint64); int copyout(pagetable_t, uint64, char *, uint64); 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; diff --git a/user/usertests.c b/user/usertests.c index 0aafe73..ef70bfb 100644 --- a/user/usertests.c +++ b/user/usertests.c @@ -1473,7 +1473,7 @@ sbrktest(void) // can one grow address space to something big? a = sbrk(0); - amt = (BIG) - (uint64)a; + amt = BIG - (uint64)a; p = sbrk(amt); if (p != a) { printf(stdout, "sbrk test failed to grow big address space; enough phys mem?\n"); |