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vm_map_protect(): add VM_MAP_PROTECT_GROWSDOWN flag

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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
This commit is contained in:
Konstantin Belousov 2023-07-28 03:40:53 +03:00
parent b6037edbd1
commit 90049eabcf
2 changed files with 20 additions and 0 deletions
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19
sys/vm/vm_map.c
View file

@ -2758,6 +2758,7 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
vm_map_entry_t entry, first_entry, in_tran, prev_entry;
vm_object_t obj;
struct ucred *cred;
vm_offset_t orig_start;
vm_prot_t check_prot, max_prot, old_prot;
int rv;
@ -2769,8 +2770,10 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
!CONTAINS_BITS(new_maxprot, new_prot))
return (KERN_OUT_OF_BOUNDS);
orig_start = start;
again:
in_tran = NULL;
start = orig_start;
vm_map_lock(map);
if ((map->flags & MAP_WXORX) != 0 &&
@ -2793,6 +2796,22 @@ again:
if (!vm_map_lookup_entry(map, start, &first_entry))
first_entry = vm_map_entry_succ(first_entry);
if ((flags & VM_MAP_PROTECT_GROWSDOWN) != 0 &&
(first_entry->eflags & MAP_ENTRY_GROWS_DOWN) != 0) {
/*
* Handle Linux's PROT_GROWSDOWN flag.
* It means that protection is applied down to the
* whole stack, including the specified range of the
* mapped region, and the grow down region (AKA
* guard).
*/
while (!CONTAINS_BITS(first_entry->eflags,
MAP_ENTRY_GUARD | MAP_ENTRY_STACK_GAP_DN) &&
first_entry != vm_map_entry_first(map))
first_entry = vm_map_entry_pred(first_entry);
start = first_entry->start;
}
/*
* Make a first pass to check for protection violations.
*/

1
sys/vm/vm_map.h
View file

@ -522,6 +522,7 @@ vm_map_entry_succ(vm_map_entry_t entry)
#define VM_MAP_PROTECT_SET_PROT 0x0001
#define VM_MAP_PROTECT_SET_MAXPROT 0x0002
#define VM_MAP_PROTECT_GROWSDOWN 0x0004
int vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
vm_prot_t new_prot, vm_prot_t new_maxprot, int flags);