[PATCH v3 bpf-next 0/3] Improve verifier log readability

[Christy Lee <christylee@fb.com>]

Simplify verifier logs and improve readability.

Changelog:
----------
v2 -> v3:
v2: https://lore.kernel.org/all/20211215192225.1278237-1-christylee@fb.com/

Patch 1:
* Fixed typo
* Added print_all bool arg to print_verifier_state()

Patch 2:
* Changed alignment from 32 to 40, fixed off-by-one error
* Renamed print_prev_insn_state() to print_insn_state()
* Fixed formatting to make the code more readable

v1 -> v2:
v1: https://lore.kernel.org/bpf/20211213182117.682461-1-christylee@fb.com/

Patch 2/3:
* Verifier will skip insn_idx when the insn is longer than 8 bytes,
  example:
  0000000000000000 <good_prog>:
       0:	18 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00	r2 = 0 ll
       2:	63 12 00 00 00 00 00 00	*(u32 *)(r2 + 0) = r1
       3:	61 20 04 00 00 00 00 00	r0 = *(u32 *)(r2 + 4)
       4:	95 00 00 00 00 00 00 00	exit
  It's incorrect to check that prev_insn_idx = insn_idx - 1, skip this
  check and print the verifier state on the correct line.
  Before:
  0: R1=ctx(id=0,off=0,imm=0) R10=fp0
  ; a[0] = (int)(long)ctx;
  0: (18) r2 = 0xffffc900006de000
  2: R2_w=map_value(id=0,off=0,ks=4,vs=16,imm=0)
  2: (63) *(u32 *)(r2 +0) = r1
  After:
  0: R1=ctx(id=0,off=0,imm=0) R10=fp0
  ; a[0] = (int)(long)ctx;
  0: (18) r2 = 0xffffc900006de000 ; R2_w=map_value(id=0,off=0,ks=4,vs=16,imm=0)
  2: (63) *(u32 *)(r2 +0) = r1
* Track previous line logging length in env, allow aligning intsruction
  from anywhere in the verifier
* Fixed bug where the verifier printed verifier state after checking
  source memory access but before check destination memory access,
  this ensures the aligned verifier state contains all scratched
  registers

Patch 3/3:
* Added one more case where we should only log in log_level=2

Christy Lee (3):
  Only print scratched registers and stack slots to verifier logs
  Right align verifier states in verifier logs
  Only output backtracking information in log level 2

 include/linux/bpf_verifier.h                  |  10 +
 kernel/bpf/verifier.c                         | 130 ++++++++---
 .../testing/selftests/bpf/prog_tests/align.c  | 214 +++++++++---------
 3 files changed, 225 insertions(+), 129 deletions(-)

--
2.30.2