linux-kernel - [PATCH v3 0/7] x86/cfi,bpf: Fix CFI vs eBPF

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Message-Id: <20231215091216.135791411@infradead.org>
Date: Fri, 15 Dec 2023 10:12:16 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: paul.walmsley@...ive.com,
 palmer@...belt.com,
 aou@...s.berkeley.edu,
 tglx@...utronix.de,
 mingo@...hat.com,
 bp@...en8.de,
 dave.hansen@...ux.intel.com,
 x86@...nel.org,
 hpa@...or.com,
 davem@...emloft.net,
 dsahern@...nel.org,
 daniel@...earbox.net,
 andrii@...nel.org,
 martin.lau@...ux.dev,
 song@...nel.org,
 yonghong.song@...ux.dev,
 john.fastabend@...il.com,
 kpsingh@...nel.org,
 sdf@...gle.com,
 haoluo@...gle.com,
 jolsa@...nel.org,
 Arnd Bergmann <arnd@...db.de>,
 samitolvanen@...gle.com,
 keescook@...omium.org,
 nathan@...nel.org,
 ndesaulniers@...gle.com,
 linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org,
 bpf@...r.kernel.org,
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 llvm@...ts.linux.dev,
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 peterz@...radead.org
Subject: [PATCH v3 0/7] x86/cfi,bpf: Fix CFI vs eBPF

Hi!

What started with the simple observation that bpf_dispatcher_*_func() was
broken for calling CFI functions with a __nocfi calling context for FineIBT
ended up with a complete BPF wide CFI fixup.

With these changes on the BPF selftest suite passes without crashing -- there's
still a few failures, but Alexei has graciously offered to look into those.

(Alexei, I have presumed your SoB on the very last patch, please update
as you see fit)

Changes since v2 are numerous but include:
 - cfi_get_offset() -- as a means to communicate the offset (ast)
 - 5 new patches fixing various BPF internals to be CFI clean

Note: it *might* be possible to merge the
bpf_bpf_tcp_ca.c:unsupported_ops[] thing into the CFI stubs, as is
get_info will have a NULL stub, unlike the others.

---
 arch/riscv/include/asm/cfi.h   |   3 +-
 arch/riscv/kernel/cfi.c        |   2 +-
 arch/x86/include/asm/cfi.h     | 126 +++++++++++++++++++++++++++++++++++++-
 arch/x86/kernel/alternative.c  |  87 +++++++++++++++++++++++---
 arch/x86/kernel/cfi.c          |   4 +-
 arch/x86/net/bpf_jit_comp.c    | 134 +++++++++++++++++++++++++++++++++++------
 include/asm-generic/Kbuild     |   1 +
 include/linux/bpf.h            |  27 ++++++++-
 include/linux/cfi.h            |  12 ++++
 kernel/bpf/bpf_struct_ops.c    |  16 ++---
 kernel/bpf/core.c              |  25 ++++++++
 kernel/bpf/cpumask.c           |   8 ++-
 kernel/bpf/helpers.c           |  18 +++++-
 net/bpf/bpf_dummy_struct_ops.c |  31 +++++++++-
 net/bpf/test_run.c             |  15 ++++-
 net/ipv4/bpf_tcp_ca.c          |  69 +++++++++++++++++++++
 16 files changed, 528 insertions(+), 50 deletions(-)