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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: <20241015183906.19678-B-hca@linux.ibm.com> References: <172895571278.107311.14000164546881236558.stgit@devnote2> <172895575716.107311.6784997045170009035.stgit@devnote2> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <172895575716.107311.6784997045170009035.stgit@devnote2> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: Us35ezRVuJAVPgZnL8yf-hXVmLe3f8Pi X-Proofpoint-ORIG-GUID: I6MloaO0jd-bMySZ7vuHW5gMDDRmrOF9 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 mlxlogscore=351 phishscore=0 malwarescore=0 lowpriorityscore=0 bulkscore=0 mlxscore=0 impostorscore=0 adultscore=0 suspectscore=0 priorityscore=1501 spamscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2410150126 On Tue, Oct 15, 2024 at 10:29:17AM +0900, Masami Hiramatsu (Google) wrote: > From: Masami Hiramatsu (Google) > > Use ftrace_regs instead of fgraph_ret_regs for tracing return value > on function_graph tracer because of simplifying the callback interface. > > The CONFIG_HAVE_FUNCTION_GRAPH_RETVAL is also replaced by > CONFIG_HAVE_FUNCTION_GRAPH_FREGS. > > Signed-off-by: Masami Hiramatsu (Google) ... > diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S > index 7e267ef63a7f..a9ca56ea0858 100644 > --- a/arch/s390/kernel/mcount.S > +++ b/arch/s390/kernel/mcount.S > @@ -134,14 +134,15 @@ SYM_CODE_END(ftrace_common) > SYM_FUNC_START(return_to_handler) > stmg %r2,%r5,32(%r15) > lgr %r1,%r15 > - aghi %r15,-(STACK_FRAME_OVERHEAD+__FGRAPH_RET_SIZE) > + aghi %r15,-(STACK_FRAME_OVERHEAD+STACK_FRAME_SIZE_FREGS) > stg %r1,__SF_BACKCHAIN(%r15) > - la %r3,STACK_FRAME_OVERHEAD(%r15) > - stg %r1,__FGRAPH_RET_FP(%r3) > - stg %r2,__FGRAPH_RET_GPR2(%r3) > - lgr %r2,%r3 > + la %r4,STACK_FRAME_OVERHEAD(%r15) > + stg %r2,__PT_R2(%r4) > + stg %r3,__PT_R3(%r4) > + stg %r1,__PT_R15(%r4) > + lgr %r2,%r4 > brasl %r14,ftrace_return_to_handler > - aghi %r15,STACK_FRAME_OVERHEAD+__FGRAPH_RET_SIZE > + aghi %r15,STACK_FRAME_SIZE_FREGS > lgr %r14,%r2 > lmg %r2,%r5,32(%r15) > BR_EX %r14 Why didn't you simply merge the addon patch which I provided, and which I tested? https://lore.kernel.org/all/20240916121656.20933-B-hca@linux.ibm.com That would make things much simpler... e.g. your new patch is also writing r3 to fregs, why? The stackframe allocation is also wrong. I didn't try, but I guess the above code would crash instantly.