Forks and COW situations show that we need vm objects rather than vm_files.

This is the first commit towards implementing vm object based paging with
right COW methods.

TODO

@@ -400,6 +400,58 @@ Current todo:
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 - Use shmat/shmget/shmdt to map block device areas to FS0 and start implementing the VFS.
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+todo:
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+- Generate 4 vmfiles:
+- env, stack, data, bss.
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+- Fill in env as a private file.
+  As faults occur on env, simply map file to process.
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+- Create an empty data, bss and stack file.
+  As faults occur on real data, copy on write onto proc->data file, by creating shadows.
+  As faults occur on devzero, copy on write onto proc->stack file, by creating shadows.
+  As faults occur on bss, copy on write onto proc->bss file, by creating shadows.
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+  FORK:
+  If a fork occurs, copy all vmas into new task.
+  Find all RW and VM_PRIVATE regions. All RW shadows are eligible.
+  Create a fork file for each RW/VM_PRIVATE region. E.g.
+  task->fork->data
+  task->fork->stack
+  task->fork->bss
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+  All RW/PRIVATE shadows become RO, with task->fork owners, rather than their original
+  owners e.g. proc->data, proc->stack etc. All pages under shadow are moved onto those files.
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+  Increase file refcount for forker tasks.
+  As faults occur on fork->stack/bss/data, copy on write onto proc->stack/bss/data, by making
+  shadows RW again and copying those faulted pages from fork files onto the proc->x files.
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