From: Christophe Leroy christophe.leroy@csgroup.eu Subject: mm, hugetlb: allow for "high" userspace addresses

This is a fix for commit f6795053dac8 ("mm: mmap: Allow for "high" userspace addresses") for hugetlb.

This patch adds support for "high" userspace addresses that are optionally supported on the system and have to be requested via a hint mechanism ("high" addr parameter to mmap).

Architectures such as powerpc and x86 achieve this by making changes to their architectural versions of hugetlb_get_unmapped_area() function. However, arm64 uses the generic version of that function.

So take into account arch_get_mmap_base() and arch_get_mmap_end() in hugetlb_get_unmapped_area(). To allow that, move those two macros out of mm/mmap.c into include/linux/sched/mm.h

If these macros are not defined in architectural code then they default to (TASK_SIZE) and (base) so should not introduce any behavioural changes to architectures that do not define them.

For the time being, only ARM64 is affected by this change.

Catalin (ARM64) said

: We should have fixed hugetlb_get_unmapped_area() as well when we added : support for 52-bit VA. The reason for commit f6795053dac8 was to prevent : normal mmap() from returning addresses above 48-bit by default as some : user-space had hard assumptions about this. : : It's a slight ABI change if you do this for hugetlb_get_unmapped_area() : but I doubt anyone would notice. It's more likely that the current : behaviour would cause issues, so I'd rather have them consistent. : : Basically when arm64 gained support for 52-bit addresses we did not : want user-space calling mmap() to suddenly get such high addresses, : otherwise we could have inadvertently broken some programs (similar : behaviour to x86 here). Hence we added commit f6795053dac8. But we : missed hugetlbfs which could still get such high mmap() addresses. So : in theory that's a potential regression that should have bee addressed : at the same time as commit f6795053dac8 (and before arm64 enabled : 52-bit addresses).

Link: https://lkml.kernel.org/r/ab847b6edb197bffdfe189e70fb4ac76bfe79e0d.165003374... Fixes: f6795053dac8 ("mm: mmap: Allow for "high" userspace addresses") Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu Reviewed-by: Catalin Marinas catalin.marinas@arm.com Cc: Steve Capper steve.capper@arm.com Cc: Will Deacon will.deacon@arm.com Cc: stable@vger.kernel.org [5.0.x] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/hugetlbfs/inode.c | 9 +++++---- include/linux/sched/mm.h | 8 ++++++++ mm/mmap.c | 8 -------- 3 files changed, 13 insertions(+), 12 deletions(-)

--- a/fs/hugetlbfs/inode.c~mm-hugetlbfs-allow-for-high-userspace-addresses +++ a/fs/hugetlbfs/inode.c @@ -206,7 +206,7 @@ hugetlb_get_unmapped_area_bottomup(struc info.flags = 0; info.length = len; info.low_limit = current->mm->mmap_base; - info.high_limit = TASK_SIZE; + info.high_limit = arch_get_mmap_end(addr); info.align_mask = PAGE_MASK & ~huge_page_mask(h); info.align_offset = 0; return vm_unmapped_area(&info); @@ -222,7 +222,7 @@ hugetlb_get_unmapped_area_topdown(struct info.flags = VM_UNMAPPED_AREA_TOPDOWN; info.length = len; info.low_limit = max(PAGE_SIZE, mmap_min_addr); - info.high_limit = current->mm->mmap_base; + info.high_limit = arch_get_mmap_base(addr, current->mm->mmap_base); info.align_mask = PAGE_MASK & ~huge_page_mask(h); info.align_offset = 0; addr = vm_unmapped_area(&info); @@ -237,7 +237,7 @@ hugetlb_get_unmapped_area_topdown(struct VM_BUG_ON(addr != -ENOMEM); info.flags = 0; info.low_limit = current->mm->mmap_base; - info.high_limit = TASK_SIZE; + info.high_limit = arch_get_mmap_end(addr); addr = vm_unmapped_area(&info); }

@@ -251,6 +251,7 @@ hugetlb_get_unmapped_area(struct file *f struct mm_struct *mm = current->mm; struct vm_area_struct *vma; struct hstate *h = hstate_file(file); + const unsigned long mmap_end = arch_get_mmap_end(addr);

if (len & ~huge_page_mask(h)) return -EINVAL; @@ -266,7 +267,7 @@ hugetlb_get_unmapped_area(struct file *f if (addr) { addr = ALIGN(addr, huge_page_size(h)); vma = find_vma(mm, addr); - if (TASK_SIZE - len >= addr && + if (mmap_end - len >= addr && (!vma || addr + len <= vm_start_gap(vma))) return addr; } --- a/include/linux/sched/mm.h~mm-hugetlbfs-allow-for-high-userspace-addresses +++ a/include/linux/sched/mm.h @@ -136,6 +136,14 @@ static inline void mm_update_next_owner( #endif /* CONFIG_MEMCG */

#ifdef CONFIG_MMU +#ifndef arch_get_mmap_end +#define arch_get_mmap_end(addr) (TASK_SIZE) +#endif + +#ifndef arch_get_mmap_base +#define arch_get_mmap_base(addr, base) (base) +#endif + extern void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack); extern unsigned long --- a/mm/mmap.c~mm-hugetlbfs-allow-for-high-userspace-addresses +++ a/mm/mmap.c @@ -2117,14 +2117,6 @@ unsigned long vm_unmapped_area(struct vm return addr; }

-#ifndef arch_get_mmap_end -#define arch_get_mmap_end(addr) (TASK_SIZE) -#endif - -#ifndef arch_get_mmap_base -#define arch_get_mmap_base(addr, base) (base) -#endif - /* Get an address range which is currently unmapped. * For shmat() with addr=0. * _