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Peter Anvin" , Mathieu Desnoyers , Kees Cook , Sam James Cc: Jens Remus , bpf@vger.kernel.org, linux-mm@kvack.org, Namhyung Kim , Andrii Nakryiko , "Jose E. Marchesi" , Beau Belgrave , Florian Weimer , "Carlos O'Donell" , Masami Hiramatsu , Jiri Olsa , Arnaldo Carvalho de Melo , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Heiko Carstens , Vasily Gorbik , Ilya Leoshkevich Subject: [PATCH v16 15/20] unwind_user: Flexible CFA recovery rules Date: Thu, 21 May 2026 16:25:41 +0200 Message-ID: <20260521142546.3908498-16-jremus@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260521142546.3908498-1-jremus@linux.ibm.com> References: <20260521142546.3908498-1-jremus@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: kwhKWSQeOAXgzUmfflqpuN0wDjKfueBz X-Authority-Analysis: v=2.4 cv=GYMnWwXL c=1 sm=1 tr=0 ts=6a0f15f8 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=pGLkceISAAAA:8 a=VnNF1IyMAAAA:8 a=BPVtMwLGy6aXIs-GLTYA:9 X-Proofpoint-ORIG-GUID: 6RquB8GktKPEIBT5chMdl5xPc8EKjIzb X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTIxMDE0MiBTYWx0ZWRfXyoEnIV/bfXRh isAk2DjOkMXZyrH532IbLlnMwNTmqvg9jJ9slIx1qFEHqYxd7GFsoKt95nCPvm38KS5WQByyuX8 s3AHrMWP4KkbYrpBXlbmsRCieTOJ+wxZ409zD5VsZH1tT3bnfjBCITUHivN/hvp7PclPI+/qUo7 J4Imcon2yQrobiJnqZ4SGIvXajywFoMkP8zb1ZBqjfsB+FFh0IlBLhEdh3RsMrn4RkSyA1gMmRm tPCm5JIsgmikq8dLo1zI1q5679+xTWR30GFG9pr+o7GhncOKTkFsfWnDh2IEmIFHcuYBEUTVH+p DkAXU7GdBbYJ+fERkuYjTTH72gIa1FVPoS1YLpaHDqtL45lxS+j6l14G2yG0UTPvTIBIK8qDv37 4SpW7kupcZzHz7sNkzuuapYZlGPOW3sjgnyfYh1eu2OnYebQ7wobBQ4ds1gMYcw7OeZ6UTC567r GGRTszWzSGZEpR0J++Q== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-21_02,2026-05-18_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 adultscore=0 suspectscore=0 spamscore=0 clxscore=1015 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605130000 definitions=main-2605210142 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 = SP + offset CFA = *(SP + offset) CFA = FP + offset CFA = *(FP + offset) CFA = register + offset CFA = *(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. Reviewed-by: Indu Bhagat Signed-off-by: Jens Remus --- Notes (jremus): Changes in v15: - enum unwind_user_cfa_rule, unwind_user_next_common(): Add support for SP/FP-based CFA recovery rules with dereferencing. (Sashiko AI) arch/x86/include/asm/unwind_user.h | 12 ++++++++---- include/linux/unwind_user_types.h | 22 ++++++++++++++++++++-- kernel/unwind/sframe.c | 15 +++++++++++++-- kernel/unwind/user.c | 24 ++++++++++++++++++++---- 4 files changed, 61 insertions(+), 12 deletions(-) diff --git a/arch/x86/include/asm/unwind_user.h b/arch/x86/include/asm/unwind_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 #define ARCH_INIT_USER_FP_FRAME(ws) \ - .cfa_off = 2*(ws), \ + .cfa = { \ + .rule = UNWIND_USER_CFA_RULE_FP_OFFSET,\ + .offset = 2*(ws), \ + }, \ .ra = { \ .rule = UNWIND_USER_RULE_CFA_OFFSET_DEREF,\ .offset = -1*(ws), \ @@ -29,11 +32,13 @@ static inline int unwind_user_word_size(struct pt_regs *regs) .rule = UNWIND_USER_RULE_CFA_OFFSET_DEREF,\ .offset = -2*(ws), \ }, \ - .use_fp = true, \ .outermost = false, #define ARCH_INIT_USER_FP_ENTRY_FRAME(ws) \ - .cfa_off = 1*(ws), \ + .cfa = { \ + .rule = UNWIND_USER_CFA_RULE_SP_OFFSET,\ + .offset = 1*(ws), \ + }, \ .ra = { \ .rule = UNWIND_USER_RULE_CFA_OFFSET_DEREF,\ .offset = -1*(ws), \ @@ -41,7 +46,6 @@ static inline int unwind_user_word_size(struct pt_regs *regs) .fp = { \ .rule = UNWIND_USER_RULE_RETAIN,\ }, \ - .use_fp = false, \ .outermost = false, 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..c18be5b7d586 100644 --- a/include/linux/unwind_user_types.h +++ b/include/linux/unwind_user_types.h @@ -29,6 +29,25 @@ struct unwind_stacktrace { #define UNWIND_USER_RULE_DEREF BIT(31) +enum unwind_user_cfa_rule { + UNWIND_USER_CFA_RULE_SP_OFFSET, /* CFA = SP + offset */ + UNWIND_USER_CFA_RULE_FP_OFFSET, /* CFA = FP + offset */ + UNWIND_USER_CFA_RULE_REG_OFFSET, /* CFA = register + offset */ + /* DEREF variants */ + UNWIND_USER_CFA_RULE_SP_OFFSET_DEREF = /* CFA = *(SP + offset) */ + UNWIND_USER_CFA_RULE_SP_OFFSET | UNWIND_USER_RULE_DEREF, + UNWIND_USER_CFA_RULE_FP_OFFSET_DEREF = /* CFA = *(FP + offset) */ + UNWIND_USER_CFA_RULE_FP_OFFSET | UNWIND_USER_RULE_DEREF, + UNWIND_USER_CFA_RULE_REG_OFFSET_DEREF = /* CFA = *(register + 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 = entity */ UNWIND_USER_RULE_CFA_OFFSET, /* entity = CFA + offset */ @@ -47,10 +66,9 @@ struct unwind_user_rule_data { }; 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; }; diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c index 29a874a67f32..daa97d8b0231 100644 --- a/kernel/unwind/sframe.c +++ b/kernel/unwind/sframe.c @@ -285,6 +285,18 @@ static __always_inline int __read_fre(struct sframe_section *sec, return -EFAULT; } +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) == SFRAME_BASE_REG_FP) + cfa_rule_data->rule = UNWIND_USER_CFA_RULE_FP_OFFSET; + else + cfa_rule_data->rule = UNWIND_USER_CFA_RULE_SP_OFFSET; + cfa_rule_data->offset = offset; +} + static __always_inline void sframe_init_rule_data(struct unwind_user_rule_data *rule_data, s32 offset) @@ -346,10 +358,9 @@ static __always_inline int __find_fre(struct sframe_section *sec, return -EINVAL; fre = prev_fre; - frame->cfa_off = 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 = SFRAME_V3_FRE_CFA_BASE_REG_ID(fre->info) == SFRAME_BASE_REG_FP; frame->outermost = SFRAME_V3_FRE_RA_UNDEFINED_P(fre->info); return 0; diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c index c6a2abac78e0..447061b10613 100644 --- a/kernel/unwind/user.c +++ b/kernel/unwind/user.c @@ -53,14 +53,30 @@ static int unwind_user_next_common(struct unwind_user_state *state, } /* Get the Canonical Frame Address (CFA) */ - if (frame->use_fp) { + switch (frame->cfa.rule) { + case UNWIND_USER_CFA_RULE_SP_OFFSET: + case UNWIND_USER_CFA_RULE_SP_OFFSET_DEREF: + cfa = state->sp; + break; + case UNWIND_USER_CFA_RULE_FP_OFFSET: + case UNWIND_USER_CFA_RULE_FP_OFFSET_DEREF: if (state->fp < state->sp) return -EINVAL; cfa = state->fp; - } else { - cfa = 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 += frame->cfa_off; + cfa += frame->cfa.offset; + if (frame->cfa.rule & UNWIND_USER_RULE_DEREF && + get_user_word(&cfa, cfa, 0, state->ws)) + return -EINVAL; /* * Make sure that stack is not going in wrong direction. Allow SP -- 2.51.0