[PATCH 0/3] RFC: add init_allocations=1 boot option

[Alexander Potapenko <glider@google.com>]

Following the recent discussions here's another take at initializing
pages and heap objects with zeroes. This is needed to prevent possible
information leaks and make the control-flow bugs that depend on
uninitialized values more deterministic.

The patchset introduces a new boot option, init_allocations, which
makes page allocator and SL[AOU]B initialize newly allocated memory.
init_allocations=0 doesn't (hopefully) add any overhead to the
allocation fast path (no noticeable slowdown on hackbench).

With only the the first of the proposed patches the slowdown numbers are:
 - 1.1% (stdev 0.2%) sys time slowdown building Linux kernel
 - 3.1% (stdev 0.3%) sys time slowdown on af_inet_loopback benchmark
 - 9.4% (stdev 0.5%) sys time slowdown on hackbench

The second patch introduces a GFP flag that allows to disable
initialization for certain allocations. The third page is an example of
applying it to af_unix.c, which helps hackbench greatly.

Slowdown numbers for the whole patchset are:
 - 1.8% (stdev 0.8%) on kernel build
 - 6.5% (stdev 0.2%) on af_inet_loopback
 - 0.12% (stdev 0.6%) on hackbench


Alexander Potapenko (3):
  mm: security: introduce the init_allocations=1 boot option
  gfp: mm: introduce __GFP_NOINIT
  net: apply __GFP_NOINIT to AF_UNIX sk_buff allocations

 drivers/infiniband/core/uverbs_ioctl.c |  2 +-
 include/linux/gfp.h                    |  6 ++++-
 include/linux/mm.h                     |  8 +++++++
 include/linux/slab_def.h               |  1 +
 include/linux/slub_def.h               |  1 +
 include/net/sock.h                     |  5 +++++
 kernel/kexec_core.c                    |  4 ++--
 mm/dmapool.c                           |  2 +-
 mm/page_alloc.c                        | 18 ++++++++++++++-
 mm/slab.c                              | 14 ++++++------
 mm/slab.h                              |  1 +
 mm/slab_common.c                       | 15 +++++++++++++
 mm/slob.c                              |  3 ++-
 mm/slub.c                              |  9 ++++----
 net/core/sock.c                        | 31 +++++++++++++++++++++-----
 net/unix/af_unix.c                     | 13 ++++++-----
 16 files changed, 104 insertions(+), 29 deletions(-)

-- 
2.21.0.392.gf8f6787159e-goog