[PATCH bpf-next v2 0/2] Use overflow.h helpers to check for overflows

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This patch set refactors kernel/bpf/verifier.c to use type-agnostic,
generic overflow-check helpers defined in include/linux/overflow.h to
check for addition and subtraction overflow, and drop the
signed_*_overflows() helpers we currently have in kernel/bpf/verifier.c.
There should be no functional change in how the verifier works.

The main motivation is to make future refactoring[1] easier.

While check_mul_overflow() also exists and could potentially replace what
we have in scalar*_min_max_mul(), it does not help with refactoring and
would either change how the verifier works (e.g. lifting restriction on
umax<=U32_MAX and u32_max<=U16_MAX) or make the code slightly harder to
read, so it is left for future endeavour.

Changes from v1 <https://lore.kernel.org/r/20240623070324.12634-1-shung-hsi.yu@xxxxxxxx>:
- use pointers to values in dst_reg directly as the sum/diff pointer and
  remove the else branch (Jiri)
- change local variables to be dst_reg pointers instead of src_reg values
- include comparison of generated assembly before & after the change
  (Alexei)

1: https://github.com/kernel-patches/bpf/pull/7205/commits

Shung-Hsi Yu (2):
  bpf: use check_add_overflow() to check for addition overflows
  bpf: use check_sub_overflow() to check for subtraction overflows

 kernel/bpf/verifier.c | 151 ++++++++++++------------------------------
 1 file changed, 42 insertions(+), 109 deletions(-)

-- 
2.45.2





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