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Thu, 28 May 2026 21:59:00 +0000 (GMT) Received: from ltcrain4-lp15.ltc.tadn.ibm.com (unknown [9.5.7.39]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 28 May 2026 21:59:00 +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 v6 3/6] selftest/bpf: Fixing powerpc JIT disassembly failure Date: Thu, 28 May 2026 21:58:52 -0400 Message-ID: <20260529015855.364704-4-adubey@linux.ibm.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260529015855.364704-1-adubey@linux.ibm.com> References: <20260529015855.364704-1-adubey@linux.ibm.com> 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-Authority-Analysis: v=2.4 cv=QLJYgALL c=1 sm=1 tr=0 ts=6a18baab cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=BG0PCUMEzKLNx9Y0HWgA:9 X-Proofpoint-GUID: Rc3DsfUURVevRQ1QSqZcHDQ1qO-gkgM8 X-Proofpoint-ORIG-GUID: Rc3DsfUURVevRQ1QSqZcHDQ1qO-gkgM8 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTI4MDIxOCBTYWx0ZWRfX4cd2W1zLjorL QWY8Rytgm1v294ZWbFWxuTGFeeD113nLzSeeznpwM2c/tuIH9SZc68Ep5YfMoRna5pNZgoxbDui hOC+bBh51Z5AkSDJEqt/6iVghpYvNYjRzs48RtWf4lpirnPKVgiEuy57Yi6nyuNucdAouKOj/L9 y5umBWIkKl6YsDjYZcoFppmLpiGzB7X43lzHmoenTqrifobL8RdmcBAy6Mbi0tpJCcl975UFSEB XHJdZrChfU/XiR76tANWAIhnT/bnkVVQ0opxEcmJmmrhEbozhtpgmrxgJgm0HxaISmC45AgDwO0 CyhfJzSLS0VxrcOOtp4NrbLvdfwOsw+HBrpCKcfuyc/cDmym7PutQPbRI+yPzZYQdmdQkL/MzlO iWuV1JGfeIUKUu3kC/DXuur5tI604fU+WbZHSJ1gMxQnFobw8tvW4nXHUMLbhTFgBVyDbaFTlnJ 1omJN52Z/5P8+DGHsoQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-05-28_04,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 impostorscore=0 malwarescore=0 adultscore=0 lowpriorityscore=0 phishscore=0 clxscore=1015 priorityscore=1501 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2605280218 From: Abhishek Dubey Ensure that the trampoline stubs JITed at the tail of the epilogue do not expose the dummy trampoline address stored in the last 8 bytes(64-bit) and last 4 bytes(32-bit) to the disassembly flow. Prevent the disassembler from ingesting this memory address, as it may occasionally decode into a seemingly valid but incorrect instruction. Fix this issue by truncating the last 8/4 bytes from JITed buffers before supplying them for disassembly. Signed-off-by: Abhishek Dubey --- .../selftests/bpf/jit_disasm_helpers.c | 23 ++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/jit_disasm_helpers.c b/tools/testing/selftests/bpf/jit_disasm_helpers.c index 364c557c5115..a6d10cf456a4 100644 --- a/tools/testing/selftests/bpf/jit_disasm_helpers.c +++ b/tools/testing/selftests/bpf/jit_disasm_helpers.c @@ -170,9 +170,11 @@ int get_jited_program_text(int fd, char *text, size_t text_sz) struct bpf_prog_info info = {}; __u32 info_len = sizeof(info); __u32 jited_funcs, len, pc; + __u32 trunc_len = 0; __u32 *func_lens = NULL; FILE *text_out = NULL; uint8_t *image = NULL; + char *triple = NULL; int i, err = 0; if (!llvm_initialized) { @@ -216,9 +218,28 @@ int get_jited_program_text(int fd, char *text, size_t text_sz) if (!ASSERT_OK(err, "bpf_prog_get_info_by_fd #2")) goto out; + /* + * last 8 bytes contains dummy_trampoline address in JIT + * output on 64-bit and last 4 bytes on 32-bit powerpc, + * which can't disassemble to a valid instruction. + */ + triple = LLVMGetDefaultTargetTriple(); + if (triple) { + if (strstr(triple, "powerpc")) { + if (IS_ENABLED(CONFIG_PPC64)) + trunc_len = 8; + else + trunc_len = 4; + } + LLVMDisposeMessage(triple); + } + for (pc = 0, i = 0; i < jited_funcs; ++i) { fprintf(text_out, "func #%d:\n", i); - disasm_one_func(text_out, image + pc, func_lens[i]); + /* Disabled JIT have zero func_lens, hence underflow */ + __u32 disasm_len = func_lens[i] > trunc_len ? + func_lens[i] - trunc_len : 0; + disasm_one_func(text_out, image + pc, disasm_len); fprintf(text_out, "\n"); pc += func_lens[i]; } -- 2.52.0