[PATCH RFC v2 3/4] mm: Support MAP_BELOW_HINT in vm_unmapped_area()
From: Charlie Jenkins <hidden>
Date: 2024-08-29 07:16:24
Also in:
linux-alpha, linux-arch, linux-kselftest, linux-mips, linux-mm, linux-s390, linux-sh, lkml, loongarch, sparclinux
Subsystem:
memory management, memory mapping, the rest · Maintainers:
Andrew Morton, Liam R. Howlett, Lorenzo Stoakes, Linus Torvalds
To ensure that all memory allocations comply with the new MAP_BELOW_HINT flag, set the high_limit in vm_unmapped_area() to the hint address + length at most. All callers to this function set the high_limit to something reasonable, usually with space for a random offset and a gap for the stack. To respect the provided high_limit, take the minimum of hint+length and the given high_limit. Signed-off-by: Charlie Jenkins <redacted> --- mm/mmap.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/mm/mmap.c b/mm/mmap.c
index 34ba0db23678..459ad380c673 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c@@ -1766,6 +1766,9 @@ unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info) { unsigned long addr; + if (info->hint != 0 && info->mmap_flags & MAP_BELOW_HINT) + info->high_limit = MIN(info->high_limit, info->hint + info->length); + if (info->flags & VM_UNMAPPED_AREA_TOPDOWN) addr = unmapped_area_topdown(info); else
--
2.45.0