[PATCH 11/16] mips: mm: Support MAP_BELOW_HINT

[Charlie Jenkins]

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 at rivosinc.com>
---
 arch/mips/mm/mmap.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index 7e11d7b58761..1595fda284cd 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -79,6 +79,13 @@ 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(info.high_limit,
+					      (addr + len) - (STACK_TOP - mm->mmap_base));
 		addr = vm_unmapped_area(&info);
 
 		if (!(addr & ~PAGE_MASK))
@@ -94,6 +101,8 @@ 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