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Marchesi" , Beau Belgrave , Linus Torvalds , Andrew Morton , Florian Weimer , Kees Cook , "Carlos O'Donell" , Sam James , Dylan Hatch , Borislav Petkov , Dave Hansen , David Hildenbrand , "H. Peter Anvin" , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , Heiko Carstens , Vasily Gorbik Subject: [PATCH v13 16/18] unwind_user/sframe: Separate reading of FRE from reading of FRE data words Date: Tue, 27 Jan 2026 16:05:51 +0100 Message-ID: <20260127150554.2760964-17-jremus@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260127150554.2760964-1-jremus@linux.ibm.com> References: <20260127150554.2760964-1-jremus@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-GUID: SxjsYwA1yXDXlqfI_eZ-2rQJjp6_np8F X-Authority-Analysis: v=2.4 cv=Uptu9uwB c=1 sm=1 tr=0 ts=6978d461 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=vUbySO9Y5rIA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=7d_E57ReAAAA:8 a=JfrnYn6hAAAA:8 a=yPCof4ZbAAAA:8 a=mDV3o1hIAAAA:8 a=yMhMjlubAAAA:8 a=VnNF1IyMAAAA:8 a=Z4Rwk6OoAAAA:8 a=20KFwNOVAAAA:8 a=7mOBRU54AAAA:8 a=RXKZOtKmAAAA:8 a=DUHKQo4JlzHLUktqRlQA:9 a=jhqOcbufqs7Y1TYCrUUU:22 a=1CNFftbPRP8L7MoqJWF3:22 a=HkZW87K1Qel5hWWM3VKY:22 a=wa9RWnbW_A1YIeRBVszw:22 a=UFF3uGjEBZWolfm0k6KQ:22 X-Proofpoint-ORIG-GUID: fzlXu4Q1sRnRiPU-AXpnORpn3NNFMVir X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTI3MDEyMSBTYWx0ZWRfXzioM6+7hU7xI /sMkYBqjJzi0bM7vkEHSWbo9KtL2QDd8gA13CQ1g/fn7oG37vvxkz2HZgYEma7S/SH8b7i4JL/D lVzJUMS0vMpgCCSm3B80VcsUcSodV2B55jE1e8h3Qf3QpEYQEcSlBbfxvCR593aWqCePmrvaNcK L5EQqE6bvzcifmYvzesAQgBPOV3nIGzNn5EiLg12Ir8EQnR+99+dtDk/RW0kSOavNO9T23utAe3 LJXZjJ3Lk0kew6LdxNDSzJkSiGc9GrOZfoqnisG1wCcPgdk16KFtHoTP86tE9L+M91orCZ5DNkH TtkNHOOerZV1ULJs4wBun6htyR5h+0qnVi6vcnTlSC+M4WJVMfXyrZIdJptf3xsrBx+tdREkiAT zk6d0iKRmO4QmD6FIrHMHXM+/P/LOcLCzzC+cqc1qAgc081XX2Vjd2Cy6cabMW7iyVz7WkI7+CQ vTJlzE2hZ0jbw1o+l6A== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-01-27_03,2026-01-27_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 priorityscore=1501 clxscore=1015 lowpriorityscore=0 phishscore=0 adultscore=0 impostorscore=0 bulkscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2601150000 definitions=main-2601270121 Content-Type: text/plain; charset="utf-8" __find_fre() performs linear search for a matching SFrame FRE for a given IP. For that purpose it uses __read_fre(), which reads the whole FRE. That is the variable-size FRE structure as well as the trailing variable-length array of variable-size data words. For the search logic to skip over the FRE it would be sufficient to read the variable-size FRE structure only, which includes the count and size of data words. Add fields to struct sframe_fre_internal to store the FRE data word's address, count, and size. Change __read_fre() to read the variable- size FRE structure only and populate those new fields. Change __read_fre_datawords() to use those new fields. Change __find_fre() to use __read_fre_datawords() to read the FRE data words only after a matching FRE has been found. Introduce safe_read_fre_datawords() and use it in sframe_validate_section() to validate that the FRE data words. Cc: Steven Rostedt Cc: Josh Poimboeuf Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Jiri Olsa Cc: Arnaldo Carvalho de Melo Cc: Namhyung Kim Cc: Thomas Gleixner Cc: Andrii Nakryiko Cc: Indu Bhagat Cc: "Jose E. Marchesi" Cc: Beau Belgrave Cc: Jens Remus Cc: Linus Torvalds Cc: Andrew Morton Cc: Florian Weimer Cc: Sam James Cc: Kees Cook Cc: "Carlos O'Donell" Signed-off-by: Jens Remus --- Notes (jremus): Changes in v13: - New patch. kernel/unwind/sframe.c | 91 +++++++++++++++++++++++++++--------------- 1 file changed, 58 insertions(+), 33 deletions(-) diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c index ebf2a2905c5c..f24997e84e05 100644 --- a/kernel/unwind/sframe.c +++ b/kernel/unwind/sframe.c @@ -39,6 +39,9 @@ struct sframe_fre_internal { u32 fp_ctl; s32 fp_off; u8 info; + unsigned long dw_addr; + unsigned char dw_count; + unsigned char dw_size; }; =20 DEFINE_STATIC_SRCU(sframe_srcu); @@ -196,11 +199,11 @@ static __always_inline int __find_fde(struct sframe_s= ection *sec, static __always_inline int __read_regular_fre_datawords(struct sframe_section *sec, struct sframe_fde_internal *fde, - unsigned long cur, - unsigned char dataword_count, - unsigned char dataword_size, struct sframe_fre_internal *fre) { + unsigned char dataword_count =3D fre->dw_count; + unsigned char dataword_size =3D fre->dw_size; + unsigned long cur =3D fre->dw_addr; s32 cfa_off, ra_off, fp_off; unsigned int cfa_regnum; =20 @@ -242,11 +245,11 @@ __read_regular_fre_datawords(struct sframe_section *s= ec, static __always_inline int __read_flex_fde_fre_datawords(struct sframe_section *sec, struct sframe_fde_internal *fde, - unsigned long cur, - unsigned char dataword_count, - unsigned char dataword_size, struct sframe_fre_internal *fre) { + unsigned char dataword_count =3D fre->dw_count; + unsigned char dataword_size =3D fre->dw_size; + unsigned long cur =3D fre->dw_addr; u32 cfa_ctl, ra_ctl, fp_ctl; s32 cfa_off, ra_off, fp_off; =20 @@ -303,24 +306,28 @@ __read_flex_fde_fre_datawords(struct sframe_section *= sec, static __always_inline int __read_fre_datawords(struct sframe_section *sec, struct sframe_fde_internal *fde, - unsigned long cur, - unsigned char dataword_count, - unsigned char dataword_size, struct sframe_fre_internal *fre) { unsigned char fde_type =3D SFRAME_V3_FDE_TYPE(fde->info2); + unsigned char dataword_count =3D fre->dw_count; + + if (!dataword_count) { + /* A FRE without data words indicates an outermost frame. */ + fre->cfa_ctl =3D 0; + fre->cfa_off =3D 0; + fre->ra_ctl =3D 0; + fre->ra_off =3D 0; + fre->fp_ctl =3D 0; + fre->fp_off =3D 0; + + return 0; + } =20 switch (fde_type) { case SFRAME_FDE_TYPE_REGULAR: - return __read_regular_fre_datawords(sec, fde, cur, - dataword_count, - dataword_size, - fre); + return __read_regular_fre_datawords(sec, fde, fre); case SFRAME_FDE_TYPE_FLEXIBLE: - return __read_flex_fde_fre_datawords(sec, fde, cur, - dataword_count, - dataword_size, - fre); + return __read_flex_fde_fre_datawords(sec, fde, fre); default: return -EFAULT; } @@ -362,23 +369,11 @@ static __always_inline int __read_fre(struct sframe_s= ection *sec, fre->size =3D addr_size + 1 + (dataword_count * dataword_size); fre->ip_off =3D ip_off; fre->info =3D info; + fre->dw_addr =3D cur; + fre->dw_count =3D dataword_count; + fre->dw_size =3D dataword_size; =20 - if (!dataword_count) { - /* - * A FRE without data words indicates RA undefined / - * outermost frame. - */ - fre->cfa_ctl =3D 0; - fre->cfa_off =3D 0; - fre->ra_ctl =3D 0; - fre->ra_off =3D 0; - fre->fp_ctl =3D 0; - fre->fp_off =3D 0; - - return 0; - } - - return __read_fre_datawords(sec, fde, cur, dataword_count, dataword_size,= fre); + return 0; =20 Efault: return -EFAULT; @@ -455,6 +450,7 @@ static __always_inline int __find_fre(struct sframe_sec= tion *sec, bool which =3D false; unsigned int i; u32 ip_off; + int ret; =20 ip_off =3D ip - fde->func_addr; =20 @@ -492,6 +488,10 @@ static __always_inline int __find_fre(struct sframe_se= ction *sec, return -EINVAL; fre =3D prev_fre; =20 + ret =3D __read_fre_datawords(sec, fde, fre); + if (ret) + return ret; + if (sframe_init_cfa_rule_data(&frame->cfa, fre->cfa_ctl, fre->cfa_off)) return -EINVAL; sframe_init_rule_data(&frame->ra, fre->ra_ctl, fre->ra_off); @@ -567,6 +567,20 @@ static int safe_read_fre(struct sframe_section *sec, return ret; } =20 +static int safe_read_fre_datawords(struct sframe_section *sec, + struct sframe_fde_internal *fde, + struct sframe_fre_internal *fre) +{ + int ret; + + if (!user_read_access_begin((void __user *)sec->sframe_start, + sec->sframe_end - sec->sframe_start)) + return -EFAULT; + ret =3D __read_fre_datawords(sec, fde, fre); + user_read_access_end(); + return ret; +} + static int sframe_validate_section(struct sframe_section *sec) { unsigned long prev_ip =3D 0; @@ -610,6 +624,17 @@ static int sframe_validate_section(struct sframe_secti= on *sec) fde.rep_size); return ret; } + ret =3D safe_read_fre_datawords(sec, &fde, fre); + if (ret) { + dbg_sec("fde %u: __read_fre_datawords(%u) failed\n", i, j); + dbg_sec("FDE: func_addr:%#lx func_size:%#x fda_off:%#x fres_off:%#x fr= es_num:%d info:%u info2:%u rep_size:%u\n", + fde.func_addr, fde.func_size, + fde.fda_off, + fde.fres_off, fde.fres_num, + fde.info, fde.info2, + fde.rep_size); + return ret; + } =20 fre_addr +=3D fre->size; =20 --=20 2.51.0