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@xxxxxxxxxxxx> --- arch/arm/mm/mmap.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c index d65d0e6ed10a..fa0c79447b78 100644 --- a/arch/arm/mm/mmap.c +++ b/arch/arm/mm/mmap.c @@ -71,6 +71,8 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, info.length = len; 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); info.align_mask = do_align ? (PAGE_MASK & (SHMLBA - 1)) : 0; info.align_offset = pgoff << PAGE_SHIFT; return vm_unmapped_area(&info); @@ -122,6 +124,12 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, info.length = len; info.low_limit = FIRST_USER_ADDRESS; 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)); info.align_mask = do_align ? (PAGE_MASK & (SHMLBA - 1)) : 0; info.align_offset = pgoff << PAGE_SHIFT; addr = vm_unmapped_area(&info); @@ -137,6 +145,8 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, info.flags = 0; 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); addr = vm_unmapped_area(&info); } -- 2.45.0
