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/s390/mm/mmap.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c index 206756946589..29e20351ca85 100644 --- a/arch/s390/mm/mmap.c +++ b/arch/s390/mm/mmap.c @@ -105,6 +105,8 @@ unsigned long 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 = get_align_mask(filp, flags); info.align_offset = pgoff << PAGE_SHIFT; addr = vm_unmapped_area(&info); @@ -143,6 +145,12 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp, unsigned long ad info.length = len; 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); info.align_mask = get_align_mask(filp, flags); info.align_offset = pgoff << PAGE_SHIFT; addr = vm_unmapped_area(&info); @@ -158,6 +166,8 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp, unsigned long ad info.flags = 0; info.low_limit = TASK_UNMAPPED_BASE; info.high_limit = TASK_SIZE; + if (flags & MAP_BELOW_HINT) + info.high_limit = MIN(TASK_SIZE, addr + len); addr = vm_unmapped_area(&info); if (offset_in_page(addr)) return addr;