git: 37e5d49e1e5e - main - vm: Fix address hints of 0 with MAP_32BIT

The branch main has been updated by alc:

URL: https://cgit.FreeBSD.org/src/commit/?id=37e5d49e1e5e750bf2a200ef2e117d14c4e9a578

commit 37e5d49e1e5e750bf2a200ef2e117d14c4e9a578
Author:     Alan Cox <alc@FreeBSD.org>
AuthorDate: 2023-08-03 07:07:14 +0000
Commit:     Alan Cox <alc@FreeBSD.org>
CommitDate: 2023-08-12 07:35:21 +0000

    vm: Fix address hints of 0 with MAP_32BIT
    
    Also, rename min_addr to default_addr, which better reflects what it
    represents.  The min_addr is not a minimum address in the same way that
    max_addr is actually a maximum address that can be allocated.  For
    example, a non-zero hint can be less than min_addr and be allocated.
    
    Reported by:    dchagin
    Reviewed by:    dchagin, kib, markj
    Fixes:  d8e6f4946cec0 "vm: Fix anonymous memory clustering under ASLR"
    Differential Revision:  https://reviews.freebsd.org/D41397
---
 sys/vm/vm_map.c  | 16 ++++++++--------
 sys/vm/vm_mmap.c | 14 ++++++++++----
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
index 8d98af7709cd..c77c00b8b5c6 100644
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -2255,19 +2255,19 @@ done:
 
 /*
  *	vm_map_find_min() is a variant of vm_map_find() that takes an
- *	additional parameter (min_addr) and treats the given address
- *	(*addr) differently.  Specifically, it treats *addr as a hint
+ *	additional parameter ("default_addr") and treats the given address
+ *	("*addr") differently.  Specifically, it treats "*addr" as a hint
  *	and not as the minimum address where the mapping is created.
  *
  *	This function works in two phases.  First, it tries to
  *	allocate above the hint.  If that fails and the hint is
- *	greater than min_addr, it performs a second pass, replacing
- *	the hint with min_addr as the minimum address for the
+ *	greater than "default_addr", it performs a second pass, replacing
+ *	the hint with "default_addr" as the minimum address for the
  *	allocation.
  */
 int
 vm_map_find_min(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
-    vm_offset_t *addr, vm_size_t length, vm_offset_t min_addr,
+    vm_offset_t *addr, vm_size_t length, vm_offset_t default_addr,
     vm_offset_t max_addr, int find_space, vm_prot_t prot, vm_prot_t max,
     int cow)
 {
@@ -2277,14 +2277,14 @@ vm_map_find_min(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
 	hint = *addr;
 	if (hint == 0) {
 		cow |= MAP_NO_HINT;
-		*addr = hint = min_addr;
+		*addr = hint = default_addr;
 	}
 	for (;;) {
 		rv = vm_map_find(map, object, offset, addr, length, max_addr,
 		    find_space, prot, max, cow);
-		if (rv == KERN_SUCCESS || min_addr >= hint)
+		if (rv == KERN_SUCCESS || default_addr >= hint)
 			return (rv);
-		*addr = hint = min_addr;
+		*addr = hint = default_addr;
 	}
 }
 
diff --git a/sys/vm/vm_mmap.c b/sys/vm/vm_mmap.c
index 7876a055ca91..d904c4f38e40 100644
--- a/sys/vm/vm_mmap.c
+++ b/sys/vm/vm_mmap.c
@@ -1555,7 +1555,7 @@ vm_mmap_object(vm_map_t map, vm_offset_t *addr, vm_size_t size, vm_prot_t prot,
     vm_prot_t maxprot, int flags, vm_object_t object, vm_ooffset_t foff,
     boolean_t writecounted, struct thread *td)
 {
-	vm_offset_t max_addr;
+	vm_offset_t default_addr, max_addr;
 	int docow, error, findspace, rv;
 	bool curmap, fitit;
 
@@ -1630,10 +1630,16 @@ vm_mmap_object(vm_map_t map, vm_offset_t *addr, vm_size_t size, vm_prot_t prot,
 			max_addr = MAP_32BIT_MAX_ADDR;
 #endif
 		if (curmap) {
-			rv = vm_map_find_min(map, object, foff, addr, size,
+			default_addr =
 			    round_page((vm_offset_t)td->td_proc->p_vmspace->
-			    vm_daddr + lim_max(td, RLIMIT_DATA)), max_addr,
-			    findspace, prot, maxprot, docow);
+			    vm_daddr + lim_max(td, RLIMIT_DATA));
+#ifdef MAP_32BIT
+			if ((flags & MAP_32BIT) != 0)
+				default_addr = 0;
+#endif
+			rv = vm_map_find_min(map, object, foff, addr, size,
+			    default_addr, max_addr, findspace, prot, maxprot,
+			    docow);
 		} else {
 			rv = vm_map_find(map, object, foff, addr, size,
 			    max_addr, findspace, prot, maxprot, docow);