linux-kernel - [PATCH bpf-next v3 0/3] Support kCFI + BPF on arm64

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Date: Tue, 7 May 2024 18:40:14 -0500
From: Maxwell Bland <mbland@...orola.com>
To: "open list:BPF [GENERAL] (Safe Dynamic Programs and Tools)" <bpf@...r.kernel.org>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Zi Shen Lim <zlim.lnx@...il.com>, Mark Rutland <mark.rutland@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mark Brown <broonie@...nel.org>, linux-arm-kernel@...ts.infradead.org,
        open list <linux-kernel@...r.kernel.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Puranjay Mohan <puranjay12@...il.com>
Subject: [PATCH bpf-next v3 0/3]  Support kCFI + BPF on arm64

In preparation for the BPF summit, I took a look back on BPF-CFI patches
to check the status and found that there had been no updates for around
a month, so I went ahead and made the fixes suggested in v2.

This patchset handles emitting proper CFI hashes during JIT, which
can cause some of the selftests to fail, and handles removing the
__nocfi tag from bpf_dispatch_*_func on ARM, meaning Clang CFI 
checks will be generated:

0000000000fea1e8 <bpf_dispatcher_xdp_func>:
paciasp
stp     x29, x30, [sp, #-0x10]!
mov     x29, sp
+ ldur    w16, [x2, #-0x4]                           
+ movk    w17, #0x1881                               
+ movk    w17, #0xd942, lsl #16                      
+ cmp     w16, w17                                
+ b.eq    0xffff8000810016a0 <bpf_dispatcher_xdp_func+0x24>
+ brk     #0x8222   
blr     x2
ldp     x29, x30, [sp], #0x10
autiasp
ret

Where ^+ indicates the additional assembly.

Credit goes to Puranjay Mohan entirely for this, I just did some fixes,
hopefully that is OK.

Cc: stable@...r.kernel.org

Changes in v2->v3:
https://lore.kernel.org/all/20240324211518.93892-1-puranjay12@gmail.com/
- Simplify cfi_get_func_hash to avoid needless failure case
- Use DEFINE_CFI_TYPE as suggested by Mark Rutland

Changes in v1->v2:
https://lore.kernel.org/bpf/20240227151115.4623-1-puranjay12@gmail.com/
- Rebased on latest bpf-next/master

Mark Rutland (1):
  cfi: add C CFI type macro

Maxwell Bland (1):
  arm64/cfi,bpf: Use DEFINE_CFI_TYPE in arm64

Puranjay Mohan (1):
  arm64/cfi,bpf: Support kCFI + BPF on arm64

 arch/arm64/include/asm/cfi.h    | 23 ++++++++++++++++++++++
 arch/arm64/kernel/alternative.c | 18 +++++++++++++++++
 arch/arm64/net/bpf_jit_comp.c   | 18 +++++++++++++++--
 arch/riscv/kernel/cfi.c         | 34 ++------------------------------
 arch/x86/kernel/alternative.c   | 35 +++------------------------------
 include/linux/cfi_types.h       | 23 ++++++++++++++++++++++
 6 files changed, 85 insertions(+), 66 deletions(-)
 create mode 100644 arch/arm64/include/asm/cfi.h


base-commit: 329a6720a3ebbc041983b267981ab2cac102de93
-- 
2.34.1