vm_map_protect(): add VM_MAP_PROTECT_GROWSDOWN flag
which requests to propagate lowest stack segment protection to the grow gap. This seems to be required for Linux emulation. Reported by: dchagin Reviewed by: alc, markj Tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D41099
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@ -2758,6 +2758,7 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
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vm_map_entry_t entry, first_entry, in_tran, prev_entry;
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vm_object_t obj;
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struct ucred *cred;
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vm_offset_t orig_start;
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vm_prot_t check_prot, max_prot, old_prot;
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int rv;
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@ -2769,8 +2770,10 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
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!CONTAINS_BITS(new_maxprot, new_prot))
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return (KERN_OUT_OF_BOUNDS);
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orig_start = start;
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again:
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in_tran = NULL;
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start = orig_start;
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vm_map_lock(map);
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if ((map->flags & MAP_WXORX) != 0 &&
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@ -2793,6 +2796,22 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
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if (!vm_map_lookup_entry(map, start, &first_entry))
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first_entry = vm_map_entry_succ(first_entry);
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if ((flags & VM_MAP_PROTECT_GROWSDOWN) != 0 &&
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(first_entry->eflags & MAP_ENTRY_GROWS_DOWN) != 0) {
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/*
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* Handle Linux's PROT_GROWSDOWN flag.
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* It means that protection is applied down to the
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* whole stack, including the specified range of the
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* mapped region, and the grow down region (AKA
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* guard).
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*/
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while (!CONTAINS_BITS(first_entry->eflags,
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MAP_ENTRY_GUARD | MAP_ENTRY_STACK_GAP_DN) &&
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first_entry != vm_map_entry_first(map))
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first_entry = vm_map_entry_pred(first_entry);
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start = first_entry->start;
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}
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/*
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* Make a first pass to check for protection violations.
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*/
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@ -522,6 +522,7 @@ vm_map_entry_succ(vm_map_entry_t entry)
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#define VM_MAP_PROTECT_SET_PROT 0x0001
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#define VM_MAP_PROTECT_SET_MAXPROT 0x0002
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#define VM_MAP_PROTECT_GROWSDOWN 0x0004
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int vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
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vm_prot_t new_prot, vm_prot_t new_maxprot, int flags);
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