Fix BPF probe memory helpers

This set adds probe_read_{user,kernel}(), probe_read_str_{user,kernel}() helpers, fixes probe_write_user() helper and selftests. For details please see individual patches.

Thanks!

v2 -> v3:
- noticed two more things that are fixed in here:
- bpf uapi helper description used 'int size' for *_str helpers, now u32
- we need TASK_SIZE_MAX + guard page on x86-64 in patch 2 otherwise we'll trigger the 00c42373d397 warn as well, so full range covered now
v1 -> v2:
- standardize unsafe_ptr terminology in uapi header comment (Andrii)
- probe_read_{user,kernel}[_str] naming scheme (Andrii)
- use global data in last test case, remove relaxed_maps (Andrii)
- add strict non-pagefault kernel read funcs to avoid warning in kernel probe read helpers (Alexei)

Daniel Borkmann (8):
uaccess: Add non-pagefault user-space write function
uaccess: Add strict non-pagefault kernel-space read function
bpf: Make use of probe_user_write in probe write helper
bpf: Add probe_read_{user,kernel} and probe_read_{user,kernel}_str helpers
bpf: Switch BPF probe insns to bpf_probe_read_kernel
bpf, samples: Use bpf_probe_read_user where appropriate
bpf, testing: Convert prog tests to probe_read_{user,kernel}{,_str} helper bpf, testing: Add selftest to read/write sockaddr from user space

 arch/x86/mm/Makefile                          |   2 +-
 arch/x86/mm/maccess.c                         |  43 ++++
 include/linux/uaccess.h                       |  16 ++
 include/uapi/linux/bpf.h                      | 122 ++++++++----
 kernel/bpf/core.c                             |   9 +-
 kernel/trace/bpf_trace.c                      | 187 +++++++++++++-----
 mm/maccess.c                                  |  70 ++++++-
 samples/bpf/map_perf_test_kern.c              |   4 +-
 samples/bpf/test_map_in_map_kern.c            |   4 +-
 samples/bpf/test_probe_write_user_kern.c      |   2 +-
 tools/include/uapi/linux/bpf.h                | 122 ++++++++----
 .../selftests/bpf/prog_tests/probe_user.c     |  78 ++++++++
 tools/testing/selftests/bpf/progs/kfree_skb.c |   4 +-
 tools/testing/selftests/bpf/progs/pyperf.h    |  67 ++++---
 .../testing/selftests/bpf/progs/strobemeta.h  |  36 ++--
 .../selftests/bpf/progs/test_probe_user.c     |  26 +++
 .../selftests/bpf/progs/test_tcp_estats.c     |   2 +-
 17 files changed, 597 insertions(+), 197 deletions(-)
 create mode 100644 arch/x86/mm/maccess.c
 create mode 100644 tools/testing/selftests/bpf/prog_tests/probe_user.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_probe_user.c

2.21.0