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Sat, 11 Apr 2026 18:13:54 +0000 (GMT) From: adubey@linux.ibm.com To: bpf@vger.kernel.org Cc: hbathini@linux.ibm.com, linuxppc-dev@lists.ozlabs.org, maddy@linux.ibm.com, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, shuah@kernel.org, linux-kselftest@vger.kernel.org, stable@vger.kernel.org, Abhishek Dubey Subject: [PATCH v3 0/5] powerpc/bpf: Add support for verifier selftest Date: Sat, 11 Apr 2026 18:14:08 -0400 Message-ID: <20260411221413.44304-1-adubey@linux.ibm.com> X-Mailer: git-send-email 2.52.0 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDExMDE1NyBTYWx0ZWRfX8oVqAZ2IBF6k BADqp/Rn8mg+oBOjqgU9MBtHh9t5PwPKwkC9NHbLlU/m9z3p0KXOFBIQGkjil9BAy77tpODQYDE 8SYazMp6fIjKiY4AEnbYKysI1ygIMSw0tffp1lwdRnuzoabFOgPI3QdkezE/xhLW+SEpe8IQZtW i1hqEUOxdZeyW7+3SLkbrrR34xopEN/mTZVgmz5t4jqAG2sywoiHMOxMUmpeI8X5biSZAiaBc2y hGfQ03e1wXRJku9W1Saz3I0pLlsm4/WaEcGuE1nadAfKsRyXutprQlb+N+63a/iqflorxcbPI2w 2rVI9CL3e5RaY0OUyQMo1zM7YQSEReXV1pcFT/WpW9uiv1CmqaG5Ron8RaCqi9Ls9dM4pTExvuy 4WamcJXfT1wvfTTwz9RvpPigVQupxDfylgzY4gGRm1tczU+waKlm70HWXyUGayFdO/KKNwcmlO9 YLgLHxi9IQLGHwGwQ3Q== X-Proofpoint-ORIG-GUID: 4ORPvybNgQe8p3vbsIEhY1igoLFOtzbh X-Authority-Analysis: v=2.4 cv=TId1jVla c=1 sm=1 tr=0 ts=69da8f6a cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=UrLCjDVe54a93DmA31EA:9 X-Proofpoint-GUID: 4ORPvybNgQe8p3vbsIEhY1igoLFOtzbh X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-11_05,2026-04-09_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 malwarescore=0 spamscore=0 adultscore=0 phishscore=0 suspectscore=0 priorityscore=1501 impostorscore=0 clxscore=1015 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604010000 definitions=main-2604110157 From: Abhishek Dubey The verifier selftest validates JITed instructions by matching expected disassembly output. The first two patches fix issues in powerpc instruction disassembly that were causing test flow failures. The fix is common for 64-bit & 32-bit powerpc. Add support for the powerpc-specific "__powerpc64" architecture tag in the third patch, enabling proper test filtering in verifier test files. Introduce verifier testcases for tailcalls on powerpc64 in the final patch. The first patch in series is fix patch, correcting memory alignment with 8-byte boundary for long branch trampoline address. The subsequent patches enables verifier selftests on powerpc. Issue Details: -------------- The Long branch stub in the trampoline implementation[1] provides flexibility to handles short as well as long branch distance to actual trampoline. Whereas, the 8 bytes long dummy_tramp_addr field sitting before long branch stub leads to failure when enabling verifier based seltest for ppc64. The verifier selftests require disassembing the final jited image to get native instructions. Later the disassembled instruction sequence is matched against sequence of instructions provided in test-file under __jited() wrapper. The final jited image contains Out-of-line stub and Long branch stub as part of epilogue jitting for a bpf program. The 8 bytes space for dummy_tramp is sandwiched between both above mentioned stubs. These 8 bytes contain memory address of dummy trampoline during trampoline invocation which don't correspond to any powerpc instructions. So, disassembly fails resulting in failure of verifier selftests. The following code snippet shows the problem with current arrangement made for dummy_tramp_addr. /* Out-of-line stub */ mflr r0 [b|bl] tramp mtlr r0 //only with OOL b bpf_func + 4 /* Long branch stub */ .long <---Invalid bytes sequence, disassembly fails mflr r11 bcl 20,31,$+4 mflr r12 ld r12, -8-SZL(r12) mtctr r12 mtlr r11 //retain ftrace ABI bctr Consider test program binary of size 112 bytes: 0: 00000060 10004de8 00002039 f8ff21f9 81ff21f8 7000e1fb 3000e13b 28: 3000e13b 2a006038 f8ff7ff8 00000039 7000e1eb 80002138 7843037d 56: 2000804e a602087c 00000060 a603087c bcffff4b c0341d00 000000c0 84: a602687d 05009f42 a602887d f0ff8ce9 a603897d a603687d 2004804e Disassembly output of above binary for ppc64le: pc:0 left:112 00 00 00 60 : nop pc:4 left:108 10 00 4d e8 : ld 2, 16(13) pc:8 left:104 00 00 20 39 : li 9, 0 pc:12 left:100 f8 ff 21 f9 : std 9, -8(1) pc:16 left:96 81 ff 21 f8 : stdu 1, -128(1) pc:20 left:92 70 00 e1 fb : std 31, 112(1) pc:24 left:88 30 00 e1 3b : addi 31, 1, 48 pc:28 left:84 30 00 e1 3b : addi 31, 1, 48 pc:32 left:80 2a 00 60 38 : li 3, 42 pc:36 left:76 f8 ff 7f f8 : std 3, -8(31) pc:40 left:72 00 00 00 39 : li 8, 0 pc:44 left:68 70 00 e1 eb : ld 31, 112(1) pc:48 left:64 80 00 21 38 : addi 1, 1, 128 pc:52 left:60 78 43 03 7d : mr 3, 8 pc:56 left:56 20 00 80 4e : blr pc:60 left:52 a6 02 08 7c : mflr 0 pc:64 left:48 00 00 00 60 : nop pc:68 left:44 a6 03 08 7c : mtlr 0 pc:72 left:40 bc ff ff 4b : b .-68 pc:76 left:36 c0 34 1d 00 : ... Failure log: Can't disasm instruction at offset 76: c0 34 1d 00 00 00 00 c0 a6 02 68 7d 05 00 9f 42 -------------------------------------- Observation: Can't disasm instruction at offset 76 as this address has ".long " (0xc0341d00000000c0) But valid instructions follow at offset 84 onwards. Move the long branch address space to the bottom of the long branch stub. This allows uninterrupted disassembly until the last 8 bytes. Exclude these last bytes from the overall program length to prevent failure in assembly generation. Following is disassembler output for same test program with moved down dummy_tramp_addr field: ..... ..... pc:68 left:44 a6 03 08 7c : mtlr 0 pc:72 left:40 bc ff ff 4b : b .-68 pc:76 left:36 a6 02 68 7d : mflr 11 pc:80 left:32 05 00 9f 42 : bcl 20, 31, .+4 pc:84 left:28 a6 02 88 7d : mflr 12 pc:88 left:24 14 00 8c e9 : ld 12, 20(12) pc:92 left:20 a6 03 89 7d : mtctr 12 pc:96 left:16 a6 03 68 7d : mtlr 11 pc:100 left:12 20 04 80 4e : bctr pc:104 left:8 c0 34 1d 00 : Failure log: Can't disasm instruction at offset 104: c0 34 1d 00 00 00 00 c0 --------------------------------------- Disassembly logic can truncate at 104, ignoring last 8 bytes. Update the dummy_tramp_addr field offset calculation from the end of the program to reflect its new location, for bpf_arch_text_poke() to update the actual trampoline's address in this field. [1] https://lore.kernel.org/all/20241030070850.1361304-18-hbathini@linux.ibm.com v2->v3: Removed fixed NOP from bottom of long branch stub Rebased on top of bpf-next v1->v2: Added fix-patch to correct memory alignment in-place Moved the optional alignmnet NOP before OOL stub [v1]: https://lore.kernel.org/bpf/20260225013627.22098-1-adubey@linux.ibm.com [v2]: https://lore.kernel.org/bpf/20260403004011.44417-1-adubey@linux.ibm.com Abhishek Dubey (5): powerpc/bpf: fix alignment of long branch trampoline address powerpc/bpf: Move out dummy_tramp_addr after Long branch stub selftest/bpf: Fixing powerpc JIT disassembly failure selftest/bpf: Enable verifier selftest for powerpc64 selftest/bpf: Add tailcall verifier selftest for powerpc64 arch/powerpc/net/bpf_jit.h | 4 +- arch/powerpc/net/bpf_jit_comp.c | 60 ++++++++++++---- arch/powerpc/net/bpf_jit_comp64.c | 4 +- .../selftests/bpf/jit_disasm_helpers.c | 13 +++- tools/testing/selftests/bpf/progs/bpf_misc.h | 1 + .../bpf/progs/verifier_tailcall_jit.c | 69 +++++++++++++++++++ tools/testing/selftests/bpf/test_loader.c | 5 ++ 7 files changed, 136 insertions(+), 20 deletions(-) -- 2.52.0