With latest llvm, bpf selftest test_progs, which has +alu32 enabled, failed for
strobemeta.o and a few other subtests. The reason is due to that
verifier did not provide better var_off.mask after jmp32 instructions.
This patch set addressed this issue and after the fix, test_progs passed
with alu32.
Patch #1 provided detailed explanation of the problem and the fix.
Patch #2 added three tests in test_verifier.
Changelog:
v1 -> v2:
- do not directly manipulate tnum.{value,mask} in __reg_bound_offset32(),
using tnum_lshift/tnum_rshift functions instead
- do __reg_bound_offset32() after regular 64bit __reg_bound_offset()
since the latter may give a better upper 32bit var_off, which can
be inherited by __reg_bound_offset32().
Yonghong Song (2):
bpf: provide better register bounds after jmp32 instructions
tools/bpf: add verifier tests for better jmp32 register bounds
kernel/bpf/verifier.c | 19 +++++
tools/testing/selftests/bpf/verifier/jmp32.c | 83 ++++++++++++++++++++
2 files changed, 102 insertions(+)
--
2.17.1
