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Peter Anvin" , Mathieu Desnoyers Subject: Re: [PATCH v16 04/18] function_graph: Replace fgraph_ret_regs with ftrace_regs Message-ID: <20241016083323.16801-A-hca@linux.ibm.com> References: <172895571278.107311.14000164546881236558.stgit@devnote2> <172895575716.107311.6784997045170009035.stgit@devnote2> <20241015183906.19678-B-hca@linux.ibm.com> <20241016084720.828fefb791af4bcf386aac91@kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241016084720.828fefb791af4bcf386aac91@kernel.org> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: THvSImdZT7cNTKydum66qvZm3KuHppMe X-Proofpoint-GUID: Ti8WhGAnHe5v38r1fomyzE9dHOz0LqKQ X-Proofpoint-UnRewURL: 0 URL was un-rewritten Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 suspectscore=0 impostorscore=0 priorityscore=1501 bulkscore=0 mlxscore=0 clxscore=1015 malwarescore=0 lowpriorityscore=0 phishscore=0 mlxlogscore=539 spamscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2410160056 On Wed, Oct 16, 2024 at 08:47:20AM +0900, Masami Hiramatsu wrote: > On Tue, 15 Oct 2024 20:39:06 +0200 > Heiko Carstens wrote: > > > That would make things much simpler... e.g. your new patch is also > > writing r3 to fregs, why? > > BTW, according to the document [1], r3 is for "return value 1", isn't it > used usually? > > [1] https://www.kernel.org/doc/Documentation/s390/Debugging390.txt That is true for the 32 bit ABI, but not for the 64 bit ABI which we care about. Besides other this is also the reason why I removed the above file five years ago: f62f7dcbf023 ("Documentation/s390: remove outdated debugging390 documentation"). If you really want to understand the 64 bit s390 ABI then you need to look at https://github.com/IBM/s390x-abi . A PDF file of the latest release is available at https://github.com/IBM/s390x-abi/releases/download/v1.6.1/lzsabi_s390x.pdf See section "1.2.5. Return Values" for return value handling. All of that said, I would appreciate if you would just merge the provided patch, unless there is a reason for not doing that. Chances are that I missed something with all the recent fregs vs ptregs changes.