[PATCH 09/16] loongarch: mm: Support MAP_BELOW_HINT

Charlie Jenkins
2024-08-28T05:49:57Z

Add support for MAP_BELOW_HINT to mmap by restricting high_limit to addr
when the flag is enabled.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
arch/loongarch/mm/mmap.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/arch/loongarch/mm/mmap.c b/arch/loongarch/mm/mmap.c
index 889030985135..66a5badf849b 100644
--- a/arch/loongarch/mm/mmap.c
+++ b/arch/loongarch/mm/mmap.c
@@ -70,6 +70,13 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,
info.flags = VM_UNMAPPED_AREA_TOPDOWN;
info.low_limit = PAGE_SIZE;
info.high_limit = mm->mmap_base;
+ if (flags & MAP_BELOW_HINT)
+ /*
+ * Subtract (STACK_TOP - mm->mmap_base) to get random
+ * offset defined in mmap_base() in mm/util.c
+ */
+ info.high_limit = MIN(mm->mmap_base,
+ (addr + len) - (STACK_TOP - mm->mmap_base))
addr = vm_unmapped_area(&info);

if (!(addr & ~PAGE_MASK))
@@ -84,7 +91,11 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,
}

info.low_limit = mm->mmap_base;
+
info.high_limit = TASK_SIZE;
+ if (flags & MAP_BELOW_HINT)
+ info.high_limit = MIN(info.high_limit, addr + len);
+
return vm_unmapped_area(&info);
}

--
2.45.0