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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 14/18] unwind_user: Flexible CFA recovery rules Date: Tue, 27 Jan 2026 16:05:49 +0100 Message-ID: <20260127150554.2760964-15-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-Spam-Details-Enc: AW1haW4tMjYwMTI3MDEyMSBTYWx0ZWRfX6cfqk7mkyDnN BKp7glWyYHb2jjLh3MumiA/bplBWiqJqruQKx/swaib6JOMAVA2drXb/+Vyi3S+6FLGjOVxX2FM xkHz3fx+zxg3nXu7uGOaaGM7hHFTc/QvHaScknYs7K7VAToz7icJnCvFXw5m0ODwgOAEzFApyMc T+m+osCzvQR5WBKDMlKs3cUo9qj90aYhdysC9ZqLsmlm2sUvv3gHo/E6NaBSwqZJ8PbhDbtRqJA uryz/Blnr9l8ZvVjyQiGS4V+d/36lXMxoA166Q6o5wit1lP06QybN6vL1gNe0jJE2BzqUQbfrQk sn9kgOczbUku7vii1yXR93Fr5shX4tnhebF2v0gG1kZAKn9Spt9hVQvCWlUYrTSXnHo1v3DAk/C TJdPERjdAZ645t4Y1JnfNpISFtf7aj/7nraVvf6JQWboLnSnPANuLA11OEp8nqTuk/Kozp1yMZd tPpJORTyQew5r8ttPhA== X-Proofpoint-GUID: Vu9HWYWmyloL_Ii75PWM7aqhnZmB2Kq3 X-Proofpoint-ORIG-GUID: mYZ-0j0k0zbvHgd1DpkIZSE_XICv4fco X-Authority-Analysis: v=2.4 cv=X+Vf6WTe c=1 sm=1 tr=0 ts=6978d460 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==: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=cmUe23YjoY9pwAX-L18A:9 a=jhqOcbufqs7Y1TYCrUUU:22 a=1CNFftbPRP8L7MoqJWF3:22 a=HkZW87K1Qel5hWWM3VKY:22 a=wa9RWnbW_A1YIeRBVszw:22 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 priorityscore=1501 suspectscore=0 impostorscore=0 lowpriorityscore=0 clxscore=1015 spamscore=0 adultscore=0 malwarescore=0 bulkscore=0 phishscore=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" To enable support for SFrame V3 flexible FDEs with a subsequent patch, add support for the following flexible Canonical Frame Address (CFA) recovery rules: CFA =3D SP + offset CFA =3D FP + offset CFA =3D register + offset CFA =3D *(register + offset) Note that CFA recovery rules that use arbitrary register contents are only valid when in the topmost frame, as their contents are otherwise unknown. 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. arch/x86/include/asm/unwind_user.h | 12 ++++++++---- include/linux/unwind_user_types.h | 18 ++++++++++++++++-- kernel/unwind/sframe.c | 15 +++++++++++++-- kernel/unwind/user.c | 22 ++++++++++++++++++---- 4 files changed, 55 insertions(+), 12 deletions(-) diff --git a/arch/x86/include/asm/unwind_user.h b/arch/x86/include/asm/unwi= nd_user.h index 9c3417be4283..f38f7c5ff1de 100644 --- a/arch/x86/include/asm/unwind_user.h +++ b/arch/x86/include/asm/unwind_user.h @@ -20,7 +20,10 @@ static inline int unwind_user_word_size(struct pt_regs *= regs) #ifdef CONFIG_HAVE_UNWIND_USER_FP =20 #define ARCH_INIT_USER_FP_FRAME(ws) \ - .cfa_off =3D 2*(ws), \ + .cfa =3D { \ + .rule =3D UNWIND_USER_CFA_RULE_FP_OFFSET,\ + .offset =3D 2*(ws), \ + }, \ .ra =3D { \ .rule =3D UNWIND_USER_RULE_CFA_OFFSET_DEREF,\ .offset =3D -1*(ws), \ @@ -29,11 +32,13 @@ static inline int unwind_user_word_size(struct pt_regs = *regs) .rule =3D UNWIND_USER_RULE_CFA_OFFSET_DEREF,\ .offset =3D -2*(ws), \ }, \ - .use_fp =3D true, \ .outermost =3D false, =20 #define ARCH_INIT_USER_FP_ENTRY_FRAME(ws) \ - .cfa_off =3D 1*(ws), \ + .cfa =3D { \ + .rule =3D UNWIND_USER_CFA_RULE_SP_OFFSET,\ + .offset =3D 1*(ws), \ + }, \ .ra =3D { \ .rule =3D UNWIND_USER_RULE_CFA_OFFSET_DEREF,\ .offset =3D -1*(ws), \ @@ -41,7 +46,6 @@ static inline int unwind_user_word_size(struct pt_regs *r= egs) .fp =3D { \ .rule =3D UNWIND_USER_RULE_RETAIN,\ }, \ - .use_fp =3D false, \ .outermost =3D false, =20 static inline bool unwind_user_at_function_start(struct pt_regs *regs) diff --git a/include/linux/unwind_user_types.h b/include/linux/unwind_user_= types.h index 0d02714a1b5d..059e5c76f2f3 100644 --- a/include/linux/unwind_user_types.h +++ b/include/linux/unwind_user_types.h @@ -29,6 +29,21 @@ struct unwind_stacktrace { =20 #define UNWIND_USER_RULE_DEREF BIT(31) =20 +enum unwind_user_cfa_rule { + UNWIND_USER_CFA_RULE_SP_OFFSET, /* CFA =3D SP + offset */ + UNWIND_USER_CFA_RULE_FP_OFFSET, /* CFA =3D FP + offset */ + UNWIND_USER_CFA_RULE_REG_OFFSET, /* CFA =3D reg + offset */ + /* DEREF variants */ + UNWIND_USER_CFA_RULE_REG_OFFSET_DEREF =3D /* CFA =3D *(reg + offset) */ + UNWIND_USER_CFA_RULE_REG_OFFSET | UNWIND_USER_RULE_DEREF, +}; + +struct unwind_user_cfa_rule_data { + enum unwind_user_cfa_rule rule; + s32 offset; + unsigned int regnum; +}; + enum unwind_user_rule { UNWIND_USER_RULE_RETAIN, /* entity =3D entity */ UNWIND_USER_RULE_CFA_OFFSET, /* entity =3D CFA + offset */ @@ -47,10 +62,9 @@ struct unwind_user_rule_data { }; =20 struct unwind_user_frame { - s32 cfa_off; + struct unwind_user_cfa_rule_data cfa; struct unwind_user_rule_data ra; struct unwind_user_rule_data fp; - bool use_fp; bool outermost; }; =20 diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c index b5301fa9dbc8..4dfc8cf2075e 100644 --- a/kernel/unwind/sframe.c +++ b/kernel/unwind/sframe.c @@ -271,6 +271,18 @@ static __always_inline int __read_fre(struct sframe_se= ction *sec, return -EFAULT; } =20 +static __always_inline void +sframe_init_cfa_rule_data(struct unwind_user_cfa_rule_data *cfa_rule_data, + unsigned char fre_info, + s32 offset) +{ + if (SFRAME_V3_FRE_CFA_BASE_REG_ID(fre_info) =3D=3D SFRAME_BASE_REG_FP) + cfa_rule_data->rule =3D UNWIND_USER_CFA_RULE_FP_OFFSET; + else + cfa_rule_data->rule =3D UNWIND_USER_CFA_RULE_SP_OFFSET; + cfa_rule_data->offset =3D offset; +} + static __always_inline void sframe_init_rule_data(struct unwind_user_rule_data *rule_data, s32 offset) @@ -332,10 +344,9 @@ static __always_inline int __find_fre(struct sframe_se= ction *sec, return -EINVAL; fre =3D prev_fre; =20 - frame->cfa_off =3D fre->cfa_off; + sframe_init_cfa_rule_data(&frame->cfa, fre->info, fre->cfa_off); sframe_init_rule_data(&frame->ra, fre->ra_off); sframe_init_rule_data(&frame->fp, fre->fp_off); - frame->use_fp =3D SFRAME_V3_FRE_CFA_BASE_REG_ID(fre->info) =3D=3D SFRAME= _BASE_REG_FP; frame->outermost =3D SFRAME_V3_FRE_RA_UNDEFINED_P(fre->info); =20 return 0; diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c index 0405922c5c0d..eb7d9489f671 100644 --- a/kernel/unwind/user.c +++ b/kernel/unwind/user.c @@ -39,14 +39,28 @@ static int unwind_user_next_common(struct unwind_user_s= tate *state, } =20 /* Get the Canonical Frame Address (CFA) */ - if (frame->use_fp) { + switch (frame->cfa.rule) { + case UNWIND_USER_CFA_RULE_SP_OFFSET: + cfa =3D state->sp; + break; + case UNWIND_USER_CFA_RULE_FP_OFFSET: if (state->fp < state->sp) return -EINVAL; cfa =3D state->fp; - } else { - cfa =3D state->sp; + break; + case UNWIND_USER_CFA_RULE_REG_OFFSET: + case UNWIND_USER_CFA_RULE_REG_OFFSET_DEREF: + if (!state->topmost || unwind_user_get_reg(&cfa, frame->cfa.regnum)) + return -EINVAL; + break; + default: + WARN_ON_ONCE(1); + return -EINVAL; } - cfa +=3D frame->cfa_off; + cfa +=3D frame->cfa.offset; + if (frame->cfa.rule & UNWIND_USER_RULE_DEREF && + get_user_word(&cfa, cfa, 0, state->ws)) + return -EINVAL; =20 /* * Make sure that stack is not going in wrong direction. Allow SP --=20 2.51.0