[PATCH v6 0/7] Increased address space for 64 bit

[Benjamin Berg <benjamin@sipsolutions.net>]

From: Benjamin Berg <benjamin.berg@intel.com>

The new version of the patchset uses execveat on a memfd instead of
cloning twice to disable rseq. This should be much more robust going
forward as it will also avoid issues with other new features like mseal.

This patchset fixes a few bugs, adds a new method of discovering the
host task size and finally adds four level page table support. All of
this means the userspace TASK_SIZE is much larger and in turns permits
userspace applications that need a lot of virtual addresses to work
fine.

One such application is ASAN which uses a fixed address in memory that
would otherwise not be addressable.

v6:
* Apply fixes pointed out by Tiwei Bie
* Add temporary file fallback as memfd is not always supported

v5:
* Use execveat with memfd instead of double clone

v4:
* Do not use WNOHANG in wait for CLONE_VFORK

v3:
* Undo incorrect change in child wait loop

v2:
* Improved double clone logic using CLONE_VFORK
* Kconfig fixes pointed out by Tiwei Bie

Benjamin Berg (7):
  um: Add generic stub_syscall6 function
  um: Add generic stub_syscall1 function
  um: use execveat to create userspace MMs
  um: Fix stub_start address calculation
  um: Limit TASK_SIZE to the addressable range
  um: Discover host_task_size from envp
  um: Add 4 level page table support

 arch/um/Kconfig                         |   1 +
 arch/um/include/asm/page.h              |  14 +-
 arch/um/include/asm/pgalloc.h           |  11 +-
 arch/um/include/asm/pgtable-4level.h    | 119 +++++++++++++++++
 arch/um/include/asm/pgtable.h           |   6 +-
 arch/um/include/shared/as-layout.h      |   2 +-
 arch/um/include/shared/os.h             |   2 +-
 arch/um/include/shared/skas/stub-data.h |  11 ++
 arch/um/kernel/mem.c                    |  17 ++-
 arch/um/kernel/um_arch.c                |  14 +-
 arch/um/os-Linux/main.c                 |   9 +-
 arch/um/os-Linux/skas/process.c         | 171 ++++++++++++++++--------
 arch/x86/um/.gitignore                  |   2 +
 arch/x86/um/Kconfig                     |  38 ++++--
 arch/x86/um/Makefile                    |  32 ++++-
 arch/x86/um/os-Linux/task_size.c        |  19 ++-
 arch/x86/um/shared/sysdep/stub_32.h     |  22 +++
 arch/x86/um/shared/sysdep/stub_64.h     |  27 ++++
 arch/x86/um/stub_elf.c                  |  86 ++++++++++++
 arch/x86/um/stub_elf_embed.S            |  11 ++
 20 files changed, 528 insertions(+), 86 deletions(-)
 create mode 100644 arch/um/include/asm/pgtable-4level.h
 create mode 100644 arch/x86/um/.gitignore
 create mode 100644 arch/x86/um/stub_elf.c
 create mode 100644 arch/x86/um/stub_elf_embed.S

-- 
2.45.2