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| author | Mole Shang <[email protected]> | 2024-02-17 11:55:33 +0800 |
|---|---|---|
| committer | Mole Shang <[email protected]> | 2024-02-17 12:22:07 +0800 |
| commit | e8e0a7b4c97064eb5e9415726d7e38aaceccd3fd (patch) | |
| tree | fb42ba5be7a8ae608b968266f62fd71fa889a89d /kernel/cow.c | |
| parent | a6af72924b115c1177d18d9b1eaba56623e4248b (diff) | |
| parent | d85aec2689c4250d0384904bdc11aa618c726bec (diff) | |
| download | xv6-labs-e8e0a7b4c97064eb5e9415726d7e38aaceccd3fd.tar.gz xv6-labs-e8e0a7b4c97064eb5e9415726d7e38aaceccd3fd.tar.bz2 xv6-labs-e8e0a7b4c97064eb5e9415726d7e38aaceccd3fd.zip | |
Merge branch 'thread' into fs
Conflicts:
.gitignore
Makefile
conf/lab.mk
kernel/param.h
Diffstat (limited to 'kernel/cow.c')
| -rw-r--r-- | kernel/cow.c | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/kernel/cow.c b/kernel/cow.c new file mode 100644 index 0000000..b3634fc --- /dev/null +++ b/kernel/cow.c @@ -0,0 +1,30 @@ +// COW pagefault handler +#include "types.h" +#include "riscv.h" +#include "defs.h" + +int +cow_handler(pagetable_t pagetable, uint64 va) +{ + // you can't really write to rediculous pointers + if(va >= MAXVA || PGROUNDDOWN(va) == 0) + return -1; + pte_t *pte = walk(pagetable, va, 0); + if(pte == 0 || (*pte & PTE_V) == 0 || (*pte & PTE_U) == 0) + return -1; + if(*pte & PTE_C){ + uint64 pa_orig = PTE2PA(*pte); + uint64 pa_new = (uint64)kalloc(); + if(pa_new == 0){ + printf("cow pagefault: kalloc failed\n"); + return -1; + } + // copy the page and add write permission + memmove((void*)pa_new, (void*)pa_orig, PGSIZE); + uint64 flags = (PTE_FLAGS(*pte) | PTE_W) & ~PTE_C; + *pte = PA2PTE(pa_new) | flags; + kfree((void*)pa_orig); + } else if ((*pte & PTE_W) == 0) + return -1; + return 0; +} |