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Subject[PATCHv2 0/5] Fix compatible mmap() return pointer over 4Gb
Changes since v1:
- Recalculate mmap_base instead of using max possible virtual address
for compat/native syscall. That will make policy for allocation the
same in 32-bit binaries and in 32-bit syscalls in 64-bit binaries.
I need this because sys_mmap() in restored 32-bit process shouldn't
hit the stack area.
- Fixed mmap() with MAP_32BIT flag in the same usecases
- used in_compat_syscall() helper rather TS_COMPAT check (Andy noticed)
- introduced find_top() helper as suggested by Andy to simplify code
- fixed test error-handeling: it checked the result of sys_mmap() with
MMAP_FAILED, which is not correct, as it calls raw syscall - now
checks return value to be aligned to PAGE_SIZE.

Description from v1 [2]:

A fix for bug in mmap() that I referenced in [1].
Also selftest for it.

I would like to mark the fix as for stable v4.9 kernel if it'll
be accepted, as I try to support compatible 32-bit C/R
after v4.9 and working compatible mmap() is really wanted there.


Cc: Thomas Gleixner <>
Cc: Ingo Molnar <>
Cc: "H. Peter Anvin" <>
Cc: Andy Lutomirski <>
Cc: Borislav Petkov <>

Dmitry Safonov (5):
x86/mm: split arch_mmap_rnd() on compat/native versions
x86/mm: introduce mmap_{,legacy}_base
x86/mm: fix native mmap() in compat bins and vice-versa
x86/mm: for MAP_32BIT check in_compat_syscall() instead TIF_ADDR32
selftests/x86: add test to check compat mmap() return addr

arch/x86/include/asm/elf.h | 14 +-
arch/x86/include/asm/processor.h | 2 +-
arch/x86/kernel/sys_x86_64.c | 48 +++++-
arch/x86/mm/hugetlbpage.c | 2 +-
arch/x86/mm/mmap.c | 56 ++++---
tools/testing/selftests/x86/Makefile | 2 +-
tools/testing/selftests/x86/test_compat_mmap.c | 208 +++++++++++++++++++++++++
7 files changed, 301 insertions(+), 31 deletions(-)
create mode 100644 tools/testing/selftests/x86/test_compat_mmap.c


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