[PATCH RFC v2 3/4] mm: Support MAP_BELOW_HINT in vm_unmapped_area()
Charlie Jenkins <[email protected]>
| Newsgroups | gmane.linux.ports.ppc64.devel,gmane.linux.kernel.cross-arch,gmane.linux.kernel,gmane.linux.ports.alpha,gmane.linux.kernel.arc,gmane.linux.ports.arm.kernel,gmane.linux.ports.mips,gmane.linux.ports.parisc,gmane.linux.ports.sh.devel,gmane.linux.ports.sparc,gmane.linux.kernel.mm |
|---|---|
| Message-ID | <[email protected]> |
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 <[email protected]> --- 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