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Wed, 20 Nov 2024 14:52:20 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 22D0520043; Wed, 20 Nov 2024 14:52:20 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4880320040; Wed, 20 Nov 2024 14:52:15 +0000 (GMT) Received: from linux.ibm.com (unknown [9.43.115.116]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTPS; Wed, 20 Nov 2024 14:52:15 +0000 (GMT) Date: Wed, 20 Nov 2024 20:22:04 +0530 From: Saket Kumar Bhaskar To: Andrii Nakryiko Cc: bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, ast@kernel.org, hbathini@linux.ibm.com, andrii@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, mykolal@fb.com Subject: Re: [PATCH 2/3] libbpf: Remove powerpc prefix from syscall function names Message-ID: References: <20241104050007.13812-1-skb99@linux.ibm.com> <20241104050007.13812-3-skb99@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: JXoZnlqt2-ISr4LiE9N74CSxrNYz-_aw X-Proofpoint-GUID: 8Y1VWVhX8SOfeQmnoWEnnjTozKzQrAjo X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 priorityscore=1501 phishscore=0 clxscore=1015 suspectscore=0 spamscore=0 impostorscore=0 bulkscore=0 mlxscore=0 adultscore=0 lowpriorityscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2411200096 On Fri, Nov 08, 2024 at 10:43:54AM -0800, Andrii Nakryiko wrote: > On Sun, Nov 3, 2024 at 9:00 PM Saket Kumar Bhaskar wrote: > > > > Since commit 94746890202cf ("powerpc: Don't add __powerpc_ prefix to > > syscall entry points") drops _powerpc prefix to syscall entry points, > > even though powerpc now supports syscall wrapper, so /proc/kallsyms > > have symbols for syscall entry without powerpc prefix(sys_*). > > > > For this reason, arch specific prefix for syscall functions in powerpc > > is dropped. > > > > Signed-off-by: Saket Kumar Bhaskar > > --- > > tools/lib/bpf/libbpf.c | 12 +++++++++--- > > 1 file changed, 9 insertions(+), 3 deletions(-) > > > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > > index 219facd0e66e..3a370fa37d8a 100644 > > --- a/tools/lib/bpf/libbpf.c > > +++ b/tools/lib/bpf/libbpf.c > > @@ -11110,9 +11110,7 @@ static const char *arch_specific_syscall_pfx(void) > > #elif defined(__riscv) > > return "riscv"; > > #elif defined(__powerpc__) > > - return "powerpc"; > > -#elif defined(__powerpc64__) > > - return "powerpc64"; > > + return ""; > > #else > > return NULL; > > #endif > > @@ -11127,7 +11125,11 @@ int probe_kern_syscall_wrapper(int token_fd) > > if (!ksys_pfx) > > return 0; > > > > +#if defined(__powerpc__) > > + snprintf(syscall_name, sizeof(syscall_name), "sys_bpf"); > > +#else > > snprintf(syscall_name, sizeof(syscall_name), "__%s_sys_bpf", ksys_pfx); > > +#endif > > The problem is that on older versions of kernel it will have this > prefix, while on newer ones it won't. So to not break anything on old > kernels, we'd need to do feature detection and pick whether to use > prefix or not, right? > > So it seems like this change needs a bit more work. > > pw-bot: cr > Hi Andrii, IMO since both the patches 7e92e01b7245(powerpc: Provide syscall wrapper) and 94746890202cf(powerpc: Don't add __powerpc_ prefix to syscall entry points) went into the same kernel version v6.1-rc1, there won't me much kernel versions that has only one of these patches. Also, to test more I tried this patch with ARCH_HAS_SYSCALL_WRAPPER disabled, and it the test passed in this case too. Thanks, Saket > > > > if (determine_kprobe_perf_type() >= 0) { > > int pfd; > > @@ -11272,8 +11274,12 @@ struct bpf_link *bpf_program__attach_ksyscall(const struct bpf_program *prog, > > * compiler does not know that we have an explicit conditional > > * as well. > > */ > > +#if defined(__powerpc__) > > + snprintf(func_name, sizeof(func_name), "sys_%s", syscall_name); > > +#else > > snprintf(func_name, sizeof(func_name), "__%s_sys_%s", > > arch_specific_syscall_pfx() ? : "", syscall_name); > > +#endif > > } else { > > snprintf(func_name, sizeof(func_name), "__se_sys_%s", syscall_name); > > } > > -- > > 2.43.5 > >