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authorFrans Kaashoek <[email protected]>2019-07-19 08:38:51 -0400
committerFrans Kaashoek <[email protected]>2019-07-19 08:38:51 -0400
commit91566327012cad2ca99df47f9321dfc012d8a7ff (patch)
treee9cb082d502a9f56857270264bea254149a3318d /spinp
parentb924e44f06c9c0882a2cffe6c9215b12c5aee2e6 (diff)
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One way of supporting a guard page below kstack: allocate kstacks in
procinit() and map them high up (below TRAMPOLNE) with an empty mapping below each stack. Never free a kernel stack. Another way would be to allocate and map them dynamically, but then we need to reload page table when switching processes in scheduler() and/or have a kernel pagetable per proc (if we want k->stack to be the same virtual address in each process). One gotcha: kernel addresses are not equal to physical addresses for stack addresses. A stack address must be translated if we need its physical address (e.g., virtio passes a stack address to the disk).
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