This series fixes the fallback of the top-down mmap: in case of
failure, a bottom-up scheme can be tried as a last resort between
the top-down mmap base and the stack, hoping for a large unused stack
limit.
Lots of architectures and even mm code start this fallback
at TASK_UNMAPPED_BASE, which is useless since the top-down scheme
already failed on the whole address space: instead, simply use
mmap_base.
Along the way, it allows to get rid of of mmap_legacy_base and
mmap_compat_legacy_base from mm_struct.
Note that arm and mips already implement this behaviour.
Alexandre Ghiti (8):
s390: Start fallback of top-down mmap at mm->mmap_base
sh: Start fallback of top-down mmap at mm->mmap_base
sparc: Start fallback of top-down mmap at mm->mmap_base
x86, hugetlbpage: Start fallback of top-down mmap at mm->mmap_base
mm: Start fallback top-down mmap at mm->mmap_base
parisc: Use mmap_base, not mmap_legacy_base, as low_limit for
bottom-up mmap
x86: Use mmap_*base, not mmap_*legacy_base, as low_limit for bottom-up
mmap
mm: Remove mmap_legacy_base and mmap_compat_legacy_code fields from
mm_struct
arch/parisc/kernel/sys_parisc.c | 8 +++-----
arch/s390/mm/mmap.c | 2 +-
arch/sh/mm/mmap.c | 2 +-
arch/sparc/kernel/sys_sparc_64.c | 2 +-
arch/sparc/mm/hugetlbpage.c | 2 +-
arch/x86/include/asm/elf.h | 2 +-
arch/x86/kernel/sys_x86_64.c | 4 ++--
arch/x86/mm/hugetlbpage.c | 7 ++++---
arch/x86/mm/mmap.c | 20 +++++++++-----------
include/linux/mm_types.h | 2 --
mm/debug.c | 4 ++--
mm/mmap.c | 2 +-
12 files changed, 26 insertions(+), 31 deletions(-)
--
2.20.1
In case of mmap failure in top-down mode, there is no need to go through
the whole address space again for the bottom-up fallback: the goal of this
fallback is to find, as a last resort, space between the top-down mmap base
and the stack, which is the only place not covered by the top-down mmap.
Signed-off-by: Alexandre Ghiti <[email protected]>
---
arch/s390/mm/mmap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index cbc718ba6d78..4a222969843b 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -166,7 +166,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
if (addr & ~PAGE_MASK) {
VM_BUG_ON(addr != -ENOMEM);
info.flags = 0;
- info.low_limit = TASK_UNMAPPED_BASE;
+ info.low_limit = mm->mmap_base;
info.high_limit = TASK_SIZE;
addr = vm_unmapped_area(&info);
if (addr & ~PAGE_MASK)
--
2.20.1
Really sorry about that, my connection is weird this morning, I'll retry
tomorrow.
Sorry again,
Alex
On 6/19/19 1:42 AM, Alexandre Ghiti wrote:
> In case of mmap failure in top-down mode, there is no need to go through
> the whole address space again for the bottom-up fallback: the goal of this
> fallback is to find, as a last resort, space between the top-down mmap base
> and the stack, which is the only place not covered by the top-down mmap.
>
> Signed-off-by: Alexandre Ghiti <[email protected]>
> ---
> arch/s390/mm/mmap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
> index cbc718ba6d78..4a222969843b 100644
> --- a/arch/s390/mm/mmap.c
> +++ b/arch/s390/mm/mmap.c
> @@ -166,7 +166,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
> if (addr & ~PAGE_MASK) {
> VM_BUG_ON(addr != -ENOMEM);
> info.flags = 0;
> - info.low_limit = TASK_UNMAPPED_BASE;
> + info.low_limit = mm->mmap_base;
> info.high_limit = TASK_SIZE;
> addr = vm_unmapped_area(&info);
> if (addr & ~PAGE_MASK)