From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5BDC4377A8A; Mon, 28 Sep 2026 06:51:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.156.1 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790578315; cv=none; b=pyHzyHO2HrPbHnqvmwA3vrmT5MluX6bFcPZpZTCeYYXZ9LghviubumixPbRjiLB33Egy70PMrpdobtj4O5WX11iMyx0W59cnvbFV3qAuQs4hKpjHpSOXK1d1fUD+8BkyK3bKF6y+xhmx7mzqCencsUL77/XpP06juj2SPCUL71w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790578315; c=relaxed/simple; bh=pZclHBw4hTRqn4zAyX+dq81xPXNnnvfu1pRcitXrswk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=aoj9eBolO04OiQp/B4HIxhtDuXKOfaJJ/jXjajOLlchSi/DfJi+I/moQWD4e3UM4L/PYstapGjEJgU9tZaS+1tBg7JoRZExuCUGZAd7IXKo1xXt5UtQbbe8AjPlRKRkQD3atMbR/kJMxMEfUN5JjeAKae00KlOccXw/TBno1h0o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com; spf=pass smtp.mailfrom=linux.ibm.com; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b=cAXu6dUh; arc=none smtp.client-ip=148.163.156.1 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.ibm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="cAXu6dUh" Received: from pps.filterd (m0356517.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 68RMPJf9847847; Mon, 28 Sep 2026 06:51:32 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=5jT551 7oJPg+1gJw1c3nS8KZ61rgm9av4UeuMlDP/oI=; b=cAXu6dUhyGJonoAiPpVDpQ 7oj9wKypwDdFlaae2u3ynrp0VyM1duvLWLCfvZEQn+w54iav4rJqjiSbaK6dGY4f 7Kzy/vsdFWSFtZNHhAu6LC38Ze0LkFyU/tI9aGqI56ttknZL9V9gphQWAvSjHeke yOjgLNFYsOb7PFiYT8SOhrArvUSgq7F1iAiaV14svG0fHpMK0y8sBZynqMb9MgMr fODt/hBZ75XfJlAm+TOsscVCX1TL89hZ3c42tf32uqxJO20+A6mHYeyJAWrYkTKL DEDZI/OAHL5xLtRX5s7nqdduDVZI9GhKmbT143lymhX7yCD6wN0yMO0HV4GbmIzQ == Received: from ppma22.wdc07v.mail.ibm.com (5c.69.3da9.ip4.static.sl-reverse.com [169.61.105.92]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4gx5s4ys6j-1 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Mon, 28 Sep 2026 06:51:31 +0000 (GMT) Received: from pps.filterd (ppma22.wdc07v.mail.ibm.com [127.0.0.1]) by ppma22.wdc07v.mail.ibm.com (8.18.1.11/8.18.1.11) with ESMTP id 68S2qUVi2024407; Mon, 28 Sep 2026 06:51:31 GMT Received: from smtprelay03.fra02v.mail.ibm.com ([9.218.2.224]) by ppma22.wdc07v.mail.ibm.com (PPS) with ESMTPS id 4gxrrw45me-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 28 Sep 2026 06:51:30 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (smtpav01.fra02v.mail.ibm.com [10.20.54.100]) by smtprelay03.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 68S6pQHT43057594 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 28 Sep 2026 06:51:26 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B919F2004B; Mon, 28 Sep 2026 06:51:26 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2627820040; Mon, 28 Sep 2026 06:51:24 +0000 (GMT) Received: from [9.89.252.119] (unknown [9.89.252.119]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 28 Sep 2026 06:51:23 +0000 (GMT) Message-ID: Date: Mon, 28 Sep 2026 12:21:22 +0530 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v14 5/5] powerpc/bpf: Move out dummy_tramp_addr after Long branch stub To: Saket Kumar Bhaskar , bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Cc: 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, venkat88@linux.ibm.com, yeswanth@linux.ibm.com References: <552225fc257381fb83d282b3040c6ad363246465.1789982239.git.skb99@linux.ibm.com> Content-Language: en-US From: Hari Bathini In-Reply-To: <552225fc257381fb83d282b3040c6ad363246465.1789982239.git.skb99@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTI4MDAyNiBTYWx0ZWRfX3yKMRnykW+cz ZMbc5taDi4GvHJBmudOvU3HxiKJP9fPzxiwdO5K0PYhc67OKm9rOwEYM5OQYq3Yj1sKYaNk4uvG xcG3liMlX8Cj9SESJuOnL13NWDS3ow4= X-Authority-Analysis: v=2.4 cv=HJ5WhYtv c=1 sm=1 tr=0 ts=6aba0e74 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=JCM8ehL5gn53L53ZUGAA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: 64RwCDLHdaVjaW0YFLc-09AVFc_1lBN0 X-Proofpoint-ORIG-GUID: 64RwCDLHdaVjaW0YFLc-09AVFc_1lBN0 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTI4MDAyNiBTYWx0ZWRfX4HpR5nwC2d7H PCdFsas9XTHSDuJoUFeZwobAibSS3BD/Rw59YBMgkuF7IshAdn+/Bbt04xh1F0nifoR1pqHxgM0 7u3ChQNlz22M+Gze3mbaKsyuDzL/iIAmz+IFxdDg3mEzz8BGxgm02RgiWZC9gzNLwF8QkGYKMiV 3CsgKcTXDK8Tomiqc+ku3o5YjhoOqSAYl847JZYN3QXwHnYT3v1D9FPfhyT9wshLZOqMx33sLzz LMJNNSK+ctI30FivzIIBDKMU5y7KbSfyDnXJ0xEeNeF/WE8ERxrLkaFDTuZsSIRaNidX0h+yUc1 otKc5a8V0tVcKfbgGNJGC5uJJAS/wiqv3xIolvqOUMsenmbig5QcH22dVNEtxq2oqcv0aRV34hT KhoPrZRnFnby7CRTQJWbOCzwevEmkxmw5R2dkx1nop4eKFm+hzARvEcQEQd3/Yt5boXTM/kqsi/ NGdb+T4w4yLgaPx3dVQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-26_05,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=0 bulkscore=0 clxscore=1015 lowpriorityscore=0 spamscore=0 impostorscore=0 phishscore=0 priorityscore=1501 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609280026 On 28/09/26 10:43 am, Saket Kumar Bhaskar wrote: > From: Abhishek Dubey > > Move the long branch address field to the bottom of the long > branch stub. This allows uninterrupted disassembly until the > last 4/8 bytes. The last bytes exclusion is logically necessary to > prevent disassembly failure, otherwise the actual program layout > is never altered. Hence no effect on overall program size. > Also, align dummy_tramp_addr field with 8-byte boundary. > > Following is disassembler output for 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. > > All BPF trampoline selftests continue to pass with this patch applied. > Looks good to me. Acked-by: Hari Bathini > Fixes: d243b62b7bd3 ("powerpc64/bpf: Add support for bpf trampolines") > Signed-off-by: Abhishek Dubey > Signed-off-by: Saket Kumar Bhaskar > Tested-by: Yeswanth Krishna Tellakula > Tested-by: R Nageswara Sastry > --- > arch/powerpc/net/bpf_jit_comp.c | 44 ++++++++++++++++++--------------- > 1 file changed, 24 insertions(+), 20 deletions(-) > > diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c > index 8ca36a933c7a..c2717f0d9cdd 100644 > --- a/arch/powerpc/net/bpf_jit_comp.c > +++ b/arch/powerpc/net/bpf_jit_comp.c > @@ -52,19 +52,19 @@ asm ( > void bpf_jit_build_fentry_stubs(u32 *image, u32 *fimage, struct codegen_context *ctx) > { > int ool_stub_idx, long_branch_stub_idx; > - int ool_stub_sz; > + int stub_sz; > > /* > + * The dummy_tramp_addr field is placed at bottom of Long branch stub. > * Align the mis-aligned dummy_tramp_addr field in the fimage. > * The alignment NOP must appear before OOL stub, to make > * ool_stub_idx & long_branch_stub_idx constant from end. > * > * The fimage can be non 8-byte aligned, so final alignment depends > - * on start of fimage and the stub's instruction count offset. The > - * OOL stub size is 4 instructions (with CONFIG_PPC_FTRACE_OUT_OF_LINE) > - * or 3 instructions (without) before dummy_tramp_addr. > - * > - * Emit a NOP here if address is not SZL aligned. > + * on start of fimage and the stub's instruction count. The > + * stubs block has 11 instructions (with CONFIG_PPC_FTRACE_OUT_OF_LINE) > + * or 10 instructions (without) before dummy_tramp_addr field. Emit a > + * NOP if the address of dummy_tramp_addr is non aligned. > * > * In pass=0 when image==NULL, conservatively account for space > * required to accommodate alignment NOP. In case final pass skips > @@ -72,8 +72,8 @@ void bpf_jit_build_fentry_stubs(u32 *image, u32 *fimage, struct codegen_context > * jited_len signifies correct program size. > */ > > - ool_stub_sz = IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE) ? 16 : 12; > - if (!image || !IS_ALIGNED((unsigned long)fimage + ctx->idx*4 + ool_stub_sz, SZL)) > + stub_sz = IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE) ? 44 : 40; > + if (!image || !IS_ALIGNED((unsigned long)fimage + ctx->idx*4 + stub_sz, SZL)) > EMIT(PPC_RAW_NOP()); > > /* > @@ -94,28 +94,29 @@ void bpf_jit_build_fentry_stubs(u32 *image, u32 *fimage, struct codegen_context > > /* > * Long branch stub: > - * .long // 8-byte aligned > * mflr r11 > * bcl 20,31,$+4 > - * mflr r12 > - * ld r12, -8-SZL(r12) > + * mflr r12 // lr/r12 stores pc of current(this) inst. > + * ld r12, 20(r12) // offset(dummy_tramp_addr) from prev inst. is 20 > * mtctr r12 > - * mtlr r11 // needed to retain ftrace ABI > + * mtlr r11 // needed to retain ftrace ABI > * bctr > + * .long // SZL bytes aligned > */ > - if (image) > - *((unsigned long *)&image[ctx->idx]) = (unsigned long)dummy_tramp; > - > - ctx->idx += SZL / 4; > long_branch_stub_idx = ctx->idx; > EMIT(PPC_RAW_MFLR(_R11)); > EMIT(PPC_RAW_BCL4()); > EMIT(PPC_RAW_MFLR(_R12)); > - EMIT(PPC_RAW_LL(_R12, _R12, -8-SZL)); > + EMIT(PPC_RAW_LL(_R12, _R12, 20)); > EMIT(PPC_RAW_MTCTR(_R12)); > EMIT(PPC_RAW_MTLR(_R11)); > EMIT(PPC_RAW_BCTR()); > > + if (image) > + *((unsigned long *)&image[ctx->idx]) = (unsigned long)dummy_tramp; > + > + ctx->idx += SZL / 4; > + > if (!bpf_jit_ool_stub) { > bpf_jit_ool_stub = (ctx->idx - ool_stub_idx) * 4; > bpf_jit_long_branch_stub = (ctx->idx - long_branch_stub_idx) * 4; > @@ -1309,6 +1310,7 @@ static void do_isync(void *info __maybe_unused) > * bpf_func: > * [nop|b] ool_stub > * 2. Out-of-line stub: > + * nop // optional nop for alignment > * ool_stub: > * mflr r0 > * [b|bl] / > @@ -1316,14 +1318,14 @@ static void do_isync(void *info __maybe_unused) > * b bpf_func + 4 > * 3. Long branch stub: > * long_branch_stub: > - * .long / > * mflr r11 > * bcl 20,31,$+4 > * mflr r12 > - * ld r12, -16(r12) > + * ld r12, 20(r12) > * mtctr r12 > * mtlr r11 // needed to retain ftrace ABI > * bctr > + * .long / > * > * dummy_tramp is used to reduce synchronization requirements. > * > @@ -1425,10 +1427,12 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t, > * 1. Update the address in the long branch stub: > * If new_addr is out of range, we will have to use the long branch stub, so patch new_addr > * here. Otherwise, revert to dummy_tramp, but only if we had patched old_addr here. > + * > + * dummy_tramp_addr moved to bottom of long branch stub. > */ > if ((new_addr && !is_offset_in_branch_range(new_addr - ip)) || > (old_addr && !is_offset_in_branch_range(old_addr - ip))) > - ret = patch_ulong((void *)(bpf_func_end - bpf_jit_long_branch_stub - SZL), > + ret = patch_ulong((void *)(bpf_func_end - SZL), /* SZL: dummy_tramp_addr offset */ > (new_addr && !is_offset_in_branch_range(new_addr - ip)) ? > (unsigned long)new_addr : (unsigned long)dummy_tramp); > if (ret)