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Rao" Subject: Re: [PATCH v2 12/39] x86/ibt,ftrace: Search for __fentry__ location To: andrew.cooper3@citrix.com, hjl.tools@gmail.com, joao@overdrivepizza.com, jpoimboe@redhat.com, Peter Zijlstra , x86@kernel.org Cc: alexei.starovoitov@gmail.com, alyssa.milburn@intel.com, keescook@chromium.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, mbenes@suse.cz, mhiramat@kernel.org, ndesaulniers@google.com, rostedt@goodmis.org, samitolvanen@google.com References: <20220224145138.952963315@infradead.org> <20220224151322.714815604@infradead.org> In-Reply-To: <20220224151322.714815604@infradead.org> MIME-Version: 1.0 User-Agent: astroid/4d6b06ad (https://github.com/astroidmail/astroid) Message-Id: <1646238087.afjf09xr2j.naveen@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-GUID: SkRKCoQCZ7dl2feNbEMk1eRAkiPwxr4U X-Proofpoint-ORIG-GUID: ZSVhR5uNO1x7LtpaBXolgpK0ciyj9Ej8 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.64.514 definitions=2022-03-02_12,2022-02-26_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 mlxlogscore=862 phishscore=0 adultscore=0 malwarescore=0 mlxscore=0 suspectscore=0 impostorscore=0 spamscore=0 clxscore=1011 bulkscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2203020071 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra wrote: > Have ftrace_location() search the symbol for the __fentry__ location > when it isn't at func+0 and use this for {,un}register_ftrace_direct(). >=20 > This avoids a whole bunch of assumptions about __fentry__ being at > func+0. >=20 > Suggested-by: Steven Rostedt > Signed-off-by: Peter Zijlstra (Intel) > --- > kernel/trace/ftrace.c | 30 ++++++++++++++++++++++++++++-- > 1 file changed, 28 insertions(+), 2 deletions(-) >=20 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -1578,7 +1578,24 @@ unsigned long ftrace_location_range(unsi > */ > unsigned long ftrace_location(unsigned long ip) > { > - return ftrace_location_range(ip, ip); > + struct dyn_ftrace *rec; > + unsigned long offset; > + unsigned long size; > + > + rec =3D lookup_rec(ip, ip); > + if (!rec) { > + if (!kallsyms_lookup_size_offset(ip, &size, &offset)) > + goto out; > + > + if (!offset) > + rec =3D lookup_rec(ip - offset, (ip - offset) + size); > + } > + > + if (rec) > + return rec->ip; > + > +out: > + return 0; > } > =20 > /** > @@ -5110,11 +5127,16 @@ int register_ftrace_direct(unsigned long > struct ftrace_func_entry *entry; > struct ftrace_hash *free_hash =3D NULL; > struct dyn_ftrace *rec; > - int ret =3D -EBUSY; > + int ret =3D -ENODEV; > =20 > mutex_lock(&direct_mutex); > =20 > + ip =3D ftrace_location(ip); > + if (!ip) > + goto out_unlock; > + > /* See if there's a direct function at @ip already */ > + ret =3D -EBUSY; > if (ftrace_find_rec_direct(ip)) > goto out_unlock; I think some of the validation at this point can be removed (diff below). > =20 > @@ -5222,6 +5244,10 @@ int unregister_ftrace_direct(unsigned lo > =20 > mutex_lock(&direct_mutex); > =20 > + ip =3D ftrace_location(ip); > + if (!ip) > + goto out_unlock; > + > entry =3D find_direct_entry(&ip, NULL); > if (!entry) > goto out_unlock; We should also update modify_ftrace_direct(). An incremental diff below. - Naveen --- diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 65d7553668ca3d..17ce4751a2051a 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5126,7 +5126,6 @@ int register_ftrace_direct(unsigned long ip, unsigned= long addr) struct ftrace_direct_func *direct; struct ftrace_func_entry *entry; struct ftrace_hash *free_hash =3D NULL; - struct dyn_ftrace *rec; int ret =3D -ENODEV; =20 mutex_lock(&direct_mutex); @@ -5140,26 +5139,6 @@ int register_ftrace_direct(unsigned long ip, unsigne= d long addr) if (ftrace_find_rec_direct(ip)) goto out_unlock; =20 - ret =3D -ENODEV; - rec =3D lookup_rec(ip, ip); - if (!rec) - goto out_unlock; - - /* - * Check if the rec says it has a direct call but we didn't - * find one earlier? - */ - if (WARN_ON(rec->flags & FTRACE_FL_DIRECT)) - goto out_unlock; - - /* Make sure the ip points to the exact record */ - if (ip !=3D rec->ip) { - ip =3D rec->ip; - /* Need to check this ip for a direct. */ - if (ftrace_find_rec_direct(ip)) - goto out_unlock; - } - ret =3D -ENOMEM; direct =3D ftrace_find_direct_func(addr); if (!direct) { @@ -5380,6 +5359,10 @@ int modify_ftrace_direct(unsigned long ip, mutex_lock(&direct_mutex); =20 mutex_lock(&ftrace_lock); + ip =3D ftrace_location(ip); + if (!ip) + goto out_unlock; + entry =3D find_direct_entry(&ip, &rec); if (!entry) goto out_unlock; --=20 2.35.1