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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 , "Steven Rostedt (Google)" Subject: [PATCH v15 02/20] unwind_user/sframe: Add support for reading .sframe headers Date: Wed, 20 May 2026 17:39:46 +0200 Message-ID: <20260520154004.3845823-3-jremus@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260520154004.3845823-1-jremus@linux.ibm.com> References: <20260520154004.3845823-1-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-Spam-Details-Enc: AW1haW4tMjYwNTIwMDE1MSBTYWx0ZWRfX1XVSLcrG7H6f KurXm7LSnAs0DOR1a2UG55zr6bNdqa4Tb0Zi91y/NYgWTbQLBCz5SDCq0TZIwoRK0fBLjs02ZP2 kBQmUTYPssD1VsHcF7eHo7+OqAn1zMPKyB5S7l/pZhE1F6pCPS8GmofiElTj78DnExERr5csC+9 hEC9MaRLOCsDSXVqmWfbbECbMvpGiexqK9KhKXqm3yiO28HlltEjAYYBpLlZVKwVLFzguiR8/Kd SPJI94kqFkF/TR/ss0rPVS9jKFusiW94cj2mHJGdcPAUmectyUSbIXfZuVTyYs2njBxB+RvRMmQ /YYlSgyro7R25hLrd6tjrKji0ZhQexn/DxG+gRDgDV09NXvMXOhxYH/tJ/jtdyKsjB0VkiSYMa2 e047bWBfrxaoA+NV8XMx/j2vTAud0NuZDDv5WHhgNcCoaCoqGb8vTfwBJoa/s4Ufw9zNdGc0Gni WsAgv5KsUt//OJoNtNQ== X-Authority-Analysis: v=2.4 cv=BNuDalQG c=1 sm=1 tr=0 ts=6a0dd5dd cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VwQbUJbxAAAA:8 a=CCpqsmhAAAAA:8 a=meVymXHHAAAA:8 a=pGLkceISAAAA:8 a=VnNF1IyMAAAA:8 a=n2P1YqxNjAFD8MGDs80A:9 a=ul9cdbp4aOFLsgKbc677:22 a=2JgSa4NbpEOStq-L5dxp:22 X-Proofpoint-ORIG-GUID: wdhLLsLq9gws6Xxr31fVHQt-1N207Km2 X-Proofpoint-GUID: AbugIBAPnhPyOr4ahSt9w4Zc9eJrIAqj 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=2026-05-20_03,2026-05-18_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 priorityscore=1501 malwarescore=0 impostorscore=0 suspectscore=0 lowpriorityscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605130000 definitions=main-2605200151 From: Josh Poimboeuf In preparation for unwinding user space stacks with sframe, add basic sframe compile infrastructure and support for reading the .sframe section header. sframe_add_section() reads the header and unconditionally returns an error, so it's not very useful yet. A subsequent patch will improve that. Link: https://lore.kernel.org/all/f27e8463783febfa0dabb0432a3dd6be8ad98412.1737511963.git.jpoimboe@kernel.org/ [ Jens Remus: Add support for SFrame V3. Add support for PC-relative FDE function start offset. Cleanup includes and indentation. ] Signed-off-by: Josh Poimboeuf Signed-off-by: Steven Rostedt (Google) Reviewed-by: Indu Bhagat Signed-off-by: Jens Remus --- Notes (jremus): Changes in v15: - Improve text/sframe section start/end validation. (Sashiko AI) - Use GFP_KERNEL_ACCOUNT instead of GFP_KERNEL (see memory-allocation.rst, section "Get Free Page flags"). (Sashiko AI) Changes in v14: - Rename SFRAME_FDE_TYPE_REGULAR to SFRAME_FDE_TYPE_DEFAULT to match SFrame V3 specification. (Indu) - Correct SFRAME_V3_FDE_TYPE_MASK value. Changes in v13: - Update to SFrame V3: - Add and use SFRAME_VERSION_3 definition. - Add helper macros to access SFrame V3 FDE type. - Rename SFRAME_FUNC_*() macros to SFRAME_FDE_*(). - Rename SFRAME_FDE_TYPE_PC* defines to SFRAME_FDE_PCTYPE_* and SFRAME_FUNC_FDE_TYPE() macro to SFRAME_V3_FDE_PCTYPE(). - Reword OFFSET to DATAWORD in SFRAME_FRE_OFFSET_{COUNT|SIZE}() macros. - Rename version-specific SFRAME_*() macros to SFRAME_V3_*(). - Update struct sframe_fde and rename to sframe_fde_v3: - Change field start_addr from s32 to s64 and rename to func_start_off. - Change field fres_num from u32 to u16. - New field u8 info2. - Remove u16 padding field. - Split FDE into function descriptor entry (struct sframe_fde_v3) and attributes (struct sframe_fde_v3). - Rename macro parameter "data" to "info" to hint at fde/fre info word and wrap it in parenthesis. - Group SFRAME_* definitions so that related ones are together. - Reword commit message (my changes). MAINTAINERS | 1 + arch/Kconfig | 3 + include/linux/sframe.h | 37 +++++++++++ kernel/unwind/Makefile | 3 +- kernel/unwind/sframe.c | 136 +++++++++++++++++++++++++++++++++++++++++ kernel/unwind/sframe.h | 81 ++++++++++++++++++++++++ 6 files changed, 260 insertions(+), 1 deletion(-) create mode 100644 include/linux/sframe.h create mode 100644 kernel/unwind/sframe.c create mode 100644 kernel/unwind/sframe.h diff --git a/MAINTAINERS b/MAINTAINERS index 7434e9d7b33f..a9b42b67a88d 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -27876,6 +27876,7 @@ M: Steven Rostedt S: Maintained F: arch/*/include/asm/unwind_user.h F: include/asm-generic/unwind_user.h +F: include/linux/sframe.h F: include/linux/unwind*.h F: kernel/unwind/ diff --git a/arch/Kconfig b/arch/Kconfig index e86880045158..94b2d5e8e529 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -486,6 +486,9 @@ config HAVE_UNWIND_USER_FP bool select UNWIND_USER +config HAVE_UNWIND_USER_SFRAME + bool + config HAVE_PERF_REGS bool help diff --git a/include/linux/sframe.h b/include/linux/sframe.h new file mode 100644 index 000000000000..0642595534f9 --- /dev/null +++ b/include/linux/sframe.h @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_SFRAME_H +#define _LINUX_SFRAME_H + +#ifdef CONFIG_HAVE_UNWIND_USER_SFRAME + +struct sframe_section { + unsigned long sframe_start; + unsigned long sframe_end; + unsigned long text_start; + unsigned long text_end; + + unsigned long fdes_start; + unsigned long fres_start; + unsigned long fres_end; + unsigned int num_fdes; + + signed char ra_off; + signed char fp_off; +}; + +extern int sframe_add_section(unsigned long sframe_start, unsigned long sframe_end, + unsigned long text_start, unsigned long text_end); +extern int sframe_remove_section(unsigned long sframe_addr); + +#else /* !CONFIG_HAVE_UNWIND_USER_SFRAME */ + +static inline int sframe_add_section(unsigned long sframe_start, unsigned long sframe_end, + unsigned long text_start, unsigned long text_end) +{ + return -ENOSYS; +} +static inline int sframe_remove_section(unsigned long sframe_addr) { return -ENOSYS; } + +#endif /* CONFIG_HAVE_UNWIND_USER_SFRAME */ + +#endif /* _LINUX_SFRAME_H */ diff --git a/kernel/unwind/Makefile b/kernel/unwind/Makefile index eae37bea54fd..146038165865 100644 --- a/kernel/unwind/Makefile +++ b/kernel/unwind/Makefile @@ -1 +1,2 @@ - obj-$(CONFIG_UNWIND_USER) += user.o deferred.o + obj-$(CONFIG_UNWIND_USER) += user.o deferred.o + obj-$(CONFIG_HAVE_UNWIND_USER_SFRAME) += sframe.o diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c new file mode 100644 index 000000000000..d24e9d4f8bef --- /dev/null +++ b/kernel/unwind/sframe.c @@ -0,0 +1,136 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Userspace sframe access functions + */ + +#define pr_fmt(fmt) "sframe: " fmt + +#include +#include +#include +#include +#include +#include +#include +#include + +#include "sframe.h" + +#define dbg(fmt, ...) \ + pr_debug("%s (%d): " fmt, current->comm, current->pid, ##__VA_ARGS__) + +static void free_section(struct sframe_section *sec) +{ + kfree(sec); +} + +static int sframe_read_header(struct sframe_section *sec) +{ + unsigned long header_end, fdes_start, fdes_end, fres_start, fres_end; + struct sframe_header shdr; + unsigned int num_fdes; + + if (copy_from_user(&shdr, (void __user *)sec->sframe_start, sizeof(shdr))) { + dbg("header usercopy failed\n"); + return -EFAULT; + } + + if (shdr.preamble.magic != SFRAME_MAGIC || + shdr.preamble.version != SFRAME_VERSION_3 || + !(shdr.preamble.flags & SFRAME_F_FDE_SORTED) || + !(shdr.preamble.flags & SFRAME_F_FDE_FUNC_START_PCREL) || + shdr.auxhdr_len) { + dbg("bad/unsupported sframe header\n"); + return -EINVAL; + } + + if (!shdr.num_fdes || !shdr.num_fres) { + dbg("no fde/fre entries\n"); + return -EINVAL; + } + + header_end = sec->sframe_start + SFRAME_HEADER_SIZE(shdr); + if (header_end >= sec->sframe_end) { + dbg("header doesn't fit in section\n"); + return -EINVAL; + } + + num_fdes = shdr.num_fdes; + fdes_start = header_end + shdr.fdes_off; + fdes_end = fdes_start + (num_fdes * sizeof(struct sframe_fde_v3)); + + fres_start = header_end + shdr.fres_off; + fres_end = fres_start + shdr.fre_len; + + if (fres_start < fdes_end || fres_end > sec->sframe_end) { + dbg("inconsistent fde/fre offsets\n"); + return -EINVAL; + } + + sec->num_fdes = num_fdes; + sec->fdes_start = fdes_start; + sec->fres_start = fres_start; + sec->fres_end = fres_end; + + sec->ra_off = shdr.cfa_fixed_ra_offset; + sec->fp_off = shdr.cfa_fixed_fp_offset; + + return 0; +} + +int sframe_add_section(unsigned long sframe_start, unsigned long sframe_end, + unsigned long text_start, unsigned long text_end) +{ + struct vm_area_struct *sframe_vma, *text_vma; + struct mm_struct *mm = current->mm; + struct sframe_section *sec; + int ret; + + if (sframe_start >= sframe_end || text_start >= text_end) { + dbg("invalid sframe/text address\n"); + return -EINVAL; + } + + scoped_guard(mmap_read_lock, mm) { + sframe_vma = vma_lookup(mm, sframe_start); + if (!sframe_vma || sframe_end > sframe_vma->vm_end) { + dbg("bad sframe address (0x%lx - 0x%lx)\n", + sframe_start, sframe_end); + return -EINVAL; + } + + text_vma = vma_lookup(mm, text_start); + if (!text_vma || + !(text_vma->vm_flags & VM_EXEC) || + text_end > text_vma->vm_end) { + dbg("bad text address (0x%lx - 0x%lx)\n", + text_start, text_end); + return -EINVAL; + } + } + + sec = kzalloc(sizeof(*sec), GFP_KERNEL_ACCOUNT); + if (!sec) + return -ENOMEM; + + sec->sframe_start = sframe_start; + sec->sframe_end = sframe_end; + sec->text_start = text_start; + sec->text_end = text_end; + + ret = sframe_read_header(sec); + if (ret) + goto err_free; + + /* TODO nowhere to store it yet - just free it and return an error */ + ret = -ENOSYS; + +err_free: + free_section(sec); + return ret; +} + +int sframe_remove_section(unsigned long sframe_start) +{ + return -ENOSYS; +} diff --git a/kernel/unwind/sframe.h b/kernel/unwind/sframe.h new file mode 100644 index 000000000000..fc2908e92c7b --- /dev/null +++ b/kernel/unwind/sframe.h @@ -0,0 +1,81 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * From https://www.sourceware.org/binutils/docs/sframe-spec.html + */ +#ifndef _SFRAME_H +#define _SFRAME_H + +#include + +#define SFRAME_VERSION_1 1 +#define SFRAME_VERSION_2 2 +#define SFRAME_VERSION_3 3 +#define SFRAME_MAGIC 0xdee2 + +#define SFRAME_F_FDE_SORTED 0x1 +#define SFRAME_F_FRAME_POINTER 0x2 +#define SFRAME_F_FDE_FUNC_START_PCREL 0x4 + +#define SFRAME_ABI_AARCH64_ENDIAN_BIG 1 +#define SFRAME_ABI_AARCH64_ENDIAN_LITTLE 2 +#define SFRAME_ABI_AMD64_ENDIAN_LITTLE 3 + +struct sframe_preamble { + u16 magic; + u8 version; + u8 flags; +} __packed; + +struct sframe_header { + struct sframe_preamble preamble; + u8 abi_arch; + s8 cfa_fixed_fp_offset; + s8 cfa_fixed_ra_offset; + u8 auxhdr_len; + u32 num_fdes; + u32 num_fres; + u32 fre_len; + u32 fdes_off; + u32 fres_off; +} __packed; + +#define SFRAME_HEADER_SIZE(header) \ + ((sizeof(struct sframe_header) + (header).auxhdr_len)) + +struct sframe_fde_v3 { + s64 func_start_off; + u32 func_size; + u32 fres_off; +} __packed; + +struct sframe_fda_v3 { + u16 fres_num; + u8 info; + u8 info2; + u8 rep_size; +} __packed; + +#define SFRAME_FDE_PCTYPE_INC 0 +#define SFRAME_FDE_PCTYPE_MASK 1 + +#define SFRAME_AARCH64_PAUTH_KEY_A 0 +#define SFRAME_AARCH64_PAUTH_KEY_B 1 + +#define SFRAME_V3_FDE_FRE_TYPE(info) ((info) & 0xf) +#define SFRAME_V3_FDE_PCTYPE(info) (((info) >> 4) & 0x1) +#define SFRAME_V3_AARCH64_FDE_PAUTH_KEY(info) (((info) >> 5) & 0x1) + +#define SFRAME_FDE_TYPE_DEFAULT 0 + +#define SFRAME_V3_FDE_TYPE_MASK 0x1f +#define SFRAME_V3_FDE_TYPE(info2) ((info2) & SFRAME_V3_FDE_TYPE_MASK) + +#define SFRAME_BASE_REG_FP 0 +#define SFRAME_BASE_REG_SP 1 + +#define SFRAME_V3_FRE_CFA_BASE_REG_ID(info) ((info) & 0x1) +#define SFRAME_V3_FRE_DATAWORD_COUNT(info) (((info) >> 1) & 0xf) +#define SFRAME_V3_FRE_DATAWORD_SIZE(info) (((info) >> 5) & 0x3) +#define SFRAME_V3_AARCH64_FRE_MANGLED_RA_P(info) (((info) >> 7) & 0x1) + +#endif /* _SFRAME_H */ -- 2.51.0