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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 , "Steven Rostedt (Google)" Subject: [PATCH v12 04/13] unwind_user/sframe: Add support for reading .sframe contents Date: Wed, 19 Nov 2025 14:23:14 +0100 Message-ID: <20251119132323.1281768-5-jremus@linux.ibm.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20251119132323.1281768-1-jremus@linux.ibm.com> References: <20251119132323.1281768-1-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-Authority-Analysis: v=2.4 cv=BanVE7t2 c=1 sm=1 tr=0 ts=691dc4d6 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=7d_E57ReAAAA:8 a=JfrnYn6hAAAA:8 a=yPCof4ZbAAAA:8 a=mDV3o1hIAAAA:8 a=yMhMjlubAAAA:8 a=Z4Rwk6OoAAAA:8 a=20KFwNOVAAAA:8 a=7mOBRU54AAAA:8 a=meVymXHHAAAA:8 a=-WfIxybQAAAA:8 a=-28QZkuTYErVj2SHl8MA:9 a=jhqOcbufqs7Y1TYCrUUU:22 a=1CNFftbPRP8L7MoqJWF3:22 a=HkZW87K1Qel5hWWM3VKY:22 a=wa9RWnbW_A1YIeRBVszw:22 a=2JgSa4NbpEOStq-L5dxp:22 a=KbVuYVxSu7xg536452LQ:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTE1MDAzMiBTYWx0ZWRfX162RBLxhqDp3 qdcdA2NwaHOoJaezcUkd13iF/TayUoQk0huiek0m4/ZvsoSoE/JsebTW8xsg/X+DW2Auop0IE3k wYze9YFM3uhvrjvq7+cgaOAkoD2pVPrg03PSdwVnGW7xGUvrSijyOVNjqQ2e0knLDrDgU2iVQX9 G1CzMB0Ioq9lLAXr56L1NwfGkmzp2mbWQqLpaKCD9N8QQh9dVBY6ZzFIO9qzOseGEh92rkwNKfB 5FnerNxkmzT8+acmDinr509dIj7Ia8QjJ1mOp2tRDlabK4+nea9MBTptjD97c5UkxCguglvVYNZ Q2hS0qqlqWUgBd8/2Rji6jlxuZ7K+W//0cm46qr+AJrmG7cJ8UJU9jIumhkObTnjopVDheKkaFE PmMw+53+nuxum0ENQRvqiFk8qv9TQg== X-Proofpoint-GUID: VZhm1qOSD-oxe5zgkS4edmB0kYmv7mEp X-Proofpoint-ORIG-GUID: FKZyC4gFcnNl1PaM8TWVkzvLbLtx4L7l X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-19_04,2025-11-18_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 lowpriorityscore=0 suspectscore=0 spamscore=0 impostorscore=0 priorityscore=1501 clxscore=1015 phishscore=0 bulkscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511150032 Content-Type: text/plain; charset="utf-8" From: Josh Poimboeuf In preparation for using sframe to unwind user space stacks, add an sframe_find() interface for finding the sframe information associated with a given text address. For performance, use user_read_access_begin() and the corresponding unsafe_*() accessors. Note that use of pr_debug() in uaccess-enabled regions would break noinstr validation, so there aren't any debug messages yet. That will be added in a subsequent commit. Link: https://lore.kernel.org/all/77c0d1ec143bf2a53d66c4ecb190e7e0a576fbfd.= 1737511963.git.jpoimboe@kernel.org/ Link: https://lore.kernel.org/all/b35ca3a3-8de5-4d32-8d30-d4e562f6b0de@linu= x.ibm.com/ [ Jens Remus: Add support for PC-relative FDE function start address. Simplify logic by using an internal SFrame FDE representation, whose FDE function start address field is an address instead of a PC-relative offset (from FDE). Rename struct sframe_fre to sframe_fre_internal to align with struct sframe_fde_internal. Cleanup includes. Fix checkpatch errors "spaces required around that ':'". ] 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: Josh Poimboeuf Signed-off-by: Steven Rostedt (Google) Signed-off-by: Jens Remus --- Notes (jremus): Changes in v12: - Simplify logic by using an internal SFrame FDE representation, whose FDE function start address field is an address instead of a PC-relative offset (from FDE). - Rename struct sframe_fre to sframe_fre_internal to align with struct sframe_fde_internal. - Add include of linux/unwind_user_types.h from "unwind_user/sframe: Add support for reading .sframe headers". - Fix checkpatch errors "spaces required around that ':'". =20 Changes in v11: - Support for SFrame V2 PC-relative FDE function start address. include/linux/sframe.h | 6 + kernel/unwind/sframe.c | 330 ++++++++++++++++++++++++++++++++++- kernel/unwind/sframe_debug.h | 35 ++++ 3 files changed, 367 insertions(+), 4 deletions(-) create mode 100644 kernel/unwind/sframe_debug.h diff --git a/include/linux/sframe.h b/include/linux/sframe.h index 7ea6a97ed8af..9a72209696f9 100644 --- a/include/linux/sframe.h +++ b/include/linux/sframe.h @@ -3,10 +3,14 @@ #define _LINUX_SFRAME_H =20 #include +#include +#include =20 #ifdef CONFIG_HAVE_UNWIND_USER_SFRAME =20 struct sframe_section { + struct rcu_head rcu; + unsigned long sframe_start; unsigned long sframe_end; unsigned long text_start; @@ -27,6 +31,7 @@ extern void sframe_free_mm(struct mm_struct *mm); extern int sframe_add_section(unsigned long sframe_start, unsigned long sf= rame_end, unsigned long text_start, unsigned long text_end); extern int sframe_remove_section(unsigned long sframe_addr); +extern int sframe_find(unsigned long ip, struct unwind_user_frame *frame); =20 static inline bool current_has_sframe(void) { @@ -45,6 +50,7 @@ static inline int sframe_add_section(unsigned long sframe= _start, unsigned long s return -ENOSYS; } static inline int sframe_remove_section(unsigned long sframe_addr) { retur= n -ENOSYS; } +static inline int sframe_find(unsigned long ip, struct unwind_user_frame *= frame) { return -ENOSYS; } static inline bool current_has_sframe(void) { return false; } =20 #endif /* CONFIG_HAVE_UNWIND_USER_SFRAME */ diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c index 149ce70e4229..d4ef825b1cbc 100644 --- a/kernel/unwind/sframe.c +++ b/kernel/unwind/sframe.c @@ -15,9 +15,322 @@ #include =20 #include "sframe.h" +#include "sframe_debug.h" + +struct sframe_fde_internal { + unsigned long func_start_addr; + u32 func_size; + u32 fres_off; + u32 fres_num; + u8 info; + u8 rep_size; +}; + +struct sframe_fre_internal { + unsigned int size; + u32 ip_off; + s32 cfa_off; + s32 ra_off; + s32 fp_off; + u8 info; +}; + +DEFINE_STATIC_SRCU(sframe_srcu); + +static __always_inline unsigned char fre_type_to_size(unsigned char fre_ty= pe) +{ + if (fre_type > 2) + return 0; + return 1 << fre_type; +} + +static __always_inline unsigned char offset_size_enum_to_size(unsigned cha= r off_size) +{ + if (off_size > 2) + return 0; + return 1 << off_size; +} + +static __always_inline int __read_fde(struct sframe_section *sec, + unsigned int fde_num, + struct sframe_fde_internal *fde) +{ + unsigned long fde_addr, func_addr; + struct sframe_fde _fde; + + fde_addr =3D sec->fdes_start + (fde_num * sizeof(struct sframe_fde)); + unsafe_copy_from_user(&_fde, (void __user *)fde_addr, + sizeof(struct sframe_fde), Efault); + + func_addr =3D fde_addr + _fde.start_addr; + if (func_addr < sec->text_start || func_addr > sec->text_end) + return -EINVAL; + + fde->func_start_addr =3D func_addr; + fde->func_size =3D _fde.func_size; + fde->fres_off =3D _fde.fres_off; + fde->fres_num =3D _fde.fres_num; + fde->info =3D _fde.info; + fde->rep_size =3D _fde.rep_size; + + return 0; + +Efault: + return -EFAULT; +} + +static __always_inline int __find_fde(struct sframe_section *sec, + unsigned long ip, + struct sframe_fde_internal *fde) +{ + unsigned long func_addr_low =3D 0, func_addr_high =3D ULONG_MAX; + struct sframe_fde __user *first, *low, *high, *found =3D NULL; + int ret; + + first =3D (void __user *)sec->fdes_start; + low =3D first; + high =3D first + sec->num_fdes - 1; + + while (low <=3D high) { + struct sframe_fde __user *mid; + s32 func_off; + unsigned long func_addr; + + mid =3D low + ((high - low) / 2); + + unsafe_get_user(func_off, (s32 __user *)mid, Efault); + func_addr =3D (unsigned long)mid + func_off; + + if (ip >=3D func_addr) { + if (func_addr < func_addr_low) + return -EFAULT; + + func_addr_low =3D func_addr; + + found =3D mid; + low =3D mid + 1; + } else { + if (func_addr > func_addr_high) + return -EFAULT; + + func_addr_high =3D func_addr; + + high =3D mid - 1; + } + } + + if (!found) + return -EINVAL; + + ret =3D __read_fde(sec, found - first, fde); + if (ret) + return ret; + + /* make sure it's not in a gap */ + if (ip < fde->func_start_addr || + ip >=3D fde->func_start_addr + fde->func_size) + return -EINVAL; + + return 0; + +Efault: + return -EFAULT; +} + +#define ____UNSAFE_GET_USER_INC(to, from, type, label) \ +({ \ + type __to; \ + unsafe_get_user(__to, (type __user *)from, label); \ + from +=3D sizeof(__to); \ + to =3D __to; \ +}) + +#define __UNSAFE_GET_USER_INC(to, from, size, label, u_or_s) \ +({ \ + switch (size) { \ + case 1: \ + ____UNSAFE_GET_USER_INC(to, from, u_or_s##8, label); \ + break; \ + case 2: \ + ____UNSAFE_GET_USER_INC(to, from, u_or_s##16, label); \ + break; \ + case 4: \ + ____UNSAFE_GET_USER_INC(to, from, u_or_s##32, label); \ + break; \ + default: \ + return -EFAULT; \ + } \ +}) + +#define UNSAFE_GET_USER_UNSIGNED_INC(to, from, size, label) \ + __UNSAFE_GET_USER_INC(to, from, size, label, u) + +#define UNSAFE_GET_USER_SIGNED_INC(to, from, size, label) \ + __UNSAFE_GET_USER_INC(to, from, size, label, s) + +#define UNSAFE_GET_USER_INC(to, from, size, label) \ + _Generic(to, \ + u8 : UNSAFE_GET_USER_UNSIGNED_INC(to, from, size, label), \ + u16 : UNSAFE_GET_USER_UNSIGNED_INC(to, from, size, label), \ + u32 : UNSAFE_GET_USER_UNSIGNED_INC(to, from, size, label), \ + s8 : UNSAFE_GET_USER_SIGNED_INC(to, from, size, label), \ + s16 : UNSAFE_GET_USER_SIGNED_INC(to, from, size, label), \ + s32 : UNSAFE_GET_USER_SIGNED_INC(to, from, size, label)) + +static __always_inline int __read_fre(struct sframe_section *sec, + struct sframe_fde_internal *fde, + unsigned long fre_addr, + struct sframe_fre_internal *fre) +{ + unsigned char fde_type =3D SFRAME_FUNC_FDE_TYPE(fde->info); + unsigned char fre_type =3D SFRAME_FUNC_FRE_TYPE(fde->info); + unsigned char offset_count, offset_size; + s32 cfa_off, ra_off, fp_off; + unsigned long cur =3D fre_addr; + unsigned char addr_size; + u32 ip_off; + u8 info; + + addr_size =3D fre_type_to_size(fre_type); + if (!addr_size) + return -EFAULT; + + if (fre_addr + addr_size + 1 > sec->fres_end) + return -EFAULT; + + UNSAFE_GET_USER_INC(ip_off, cur, addr_size, Efault); + if (fde_type =3D=3D SFRAME_FDE_TYPE_PCINC && ip_off > fde->func_size) + return -EFAULT; + + UNSAFE_GET_USER_INC(info, cur, 1, Efault); + offset_count =3D SFRAME_FRE_OFFSET_COUNT(info); + offset_size =3D offset_size_enum_to_size(SFRAME_FRE_OFFSET_SIZE(info)); + if (!offset_count || !offset_size) + return -EFAULT; + + if (cur + (offset_count * offset_size) > sec->fres_end) + return -EFAULT; + + fre->size =3D addr_size + 1 + (offset_count * offset_size); + + UNSAFE_GET_USER_INC(cfa_off, cur, offset_size, Efault); + offset_count--; + + ra_off =3D sec->ra_off; + if (!ra_off) { + if (!offset_count--) + return -EFAULT; + + UNSAFE_GET_USER_INC(ra_off, cur, offset_size, Efault); + } =20 -#define dbg(fmt, ...) \ - pr_debug("%s (%d): " fmt, current->comm, current->pid, ##__VA_ARGS__) + fp_off =3D sec->fp_off; + if (!fp_off && offset_count) { + offset_count--; + UNSAFE_GET_USER_INC(fp_off, cur, offset_size, Efault); + } + + if (offset_count) + return -EFAULT; + + fre->ip_off =3D ip_off; + fre->cfa_off =3D cfa_off; + fre->ra_off =3D ra_off; + fre->fp_off =3D fp_off; + fre->info =3D info; + + return 0; + +Efault: + return -EFAULT; +} + +static __always_inline int __find_fre(struct sframe_section *sec, + struct sframe_fde_internal *fde, + unsigned long ip, + struct unwind_user_frame *frame) +{ + unsigned char fde_type =3D SFRAME_FUNC_FDE_TYPE(fde->info); + struct sframe_fre_internal *fre, *prev_fre =3D NULL; + struct sframe_fre_internal fres[2]; + unsigned long fre_addr; + bool which =3D false; + unsigned int i; + u32 ip_off; + + ip_off =3D ip - fde->func_start_addr; + + if (fde_type =3D=3D SFRAME_FDE_TYPE_PCMASK) + ip_off %=3D fde->rep_size; + + fre_addr =3D sec->fres_start + fde->fres_off; + + for (i =3D 0; i < fde->fres_num; i++) { + int ret; + + /* + * Alternate between the two fre_addr[] entries for 'fre' and + * 'prev_fre'. + */ + fre =3D which ? fres : fres + 1; + which =3D !which; + + ret =3D __read_fre(sec, fde, fre_addr, fre); + if (ret) + return ret; + + fre_addr +=3D fre->size; + + if (prev_fre && fre->ip_off <=3D prev_fre->ip_off) + return -EFAULT; + + if (fre->ip_off > ip_off) + break; + + prev_fre =3D fre; + } + + if (!prev_fre) + return -EINVAL; + fre =3D prev_fre; + + frame->cfa_off =3D fre->cfa_off; + frame->ra_off =3D fre->ra_off; + frame->fp_off =3D fre->fp_off; + frame->use_fp =3D SFRAME_FRE_CFA_BASE_REG_ID(fre->info) =3D=3D SFRAME_BA= SE_REG_FP; + + return 0; +} + +int sframe_find(unsigned long ip, struct unwind_user_frame *frame) +{ + struct mm_struct *mm =3D current->mm; + struct sframe_section *sec; + struct sframe_fde_internal fde; + int ret; + + if (!mm) + return -EINVAL; + + guard(srcu)(&sframe_srcu); + + sec =3D mtree_load(&mm->sframe_mt, ip); + if (!sec) + return -EINVAL; + + if (!user_read_access_begin((void __user *)sec->sframe_start, + sec->sframe_end - sec->sframe_start)) + return -EFAULT; + + ret =3D __find_fde(sec, ip, &fde); + if (ret) + goto end; + + ret =3D __find_fre(sec, &fde, ip, frame); +end: + user_read_access_end(); + return ret; +} =20 static void free_section(struct sframe_section *sec) { @@ -120,8 +433,10 @@ int sframe_add_section(unsigned long sframe_start, uns= igned long sframe_end, sec->text_end =3D text_end; =20 ret =3D sframe_read_header(sec); - if (ret) + if (ret) { + dbg_print_header(sec); goto err_free; + } =20 ret =3D mtree_insert_range(sframe_mt, sec->text_start, sec->text_end, sec= , GFP_KERNEL); if (ret) { @@ -137,6 +452,13 @@ int sframe_add_section(unsigned long sframe_start, uns= igned long sframe_end, return ret; } =20 +static void sframe_free_srcu(struct rcu_head *rcu) +{ + struct sframe_section *sec =3D container_of(rcu, struct sframe_section, r= cu); + + free_section(sec); +} + static int __sframe_remove_section(struct mm_struct *mm, struct sframe_section *sec) { @@ -145,7 +467,7 @@ static int __sframe_remove_section(struct mm_struct *mm, return -EINVAL; } =20 - free_section(sec); + call_srcu(&sframe_srcu, &sec->rcu, sframe_free_srcu); =20 return 0; } diff --git a/kernel/unwind/sframe_debug.h b/kernel/unwind/sframe_debug.h new file mode 100644 index 000000000000..055c8c8fae24 --- /dev/null +++ b/kernel/unwind/sframe_debug.h @@ -0,0 +1,35 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _SFRAME_DEBUG_H +#define _SFRAME_DEBUG_H + +#include +#include "sframe.h" + +#ifdef CONFIG_DYNAMIC_DEBUG + +#define dbg(fmt, ...) \ + pr_debug("%s (%d): " fmt, current->comm, current->pid, ##__VA_ARGS__) + +static __always_inline void dbg_print_header(struct sframe_section *sec) +{ + unsigned long fdes_end; + + fdes_end =3D sec->fdes_start + (sec->num_fdes * sizeof(struct sframe_fde)= ); + + dbg("SEC: sframe:0x%lx-0x%lx text:0x%lx-0x%lx " + "fdes:0x%lx-0x%lx fres:0x%lx-0x%lx " + "ra_off:%d fp_off:%d\n", + sec->sframe_start, sec->sframe_end, sec->text_start, sec->text_end, + sec->fdes_start, fdes_end, sec->fres_start, sec->fres_end, + sec->ra_off, sec->fp_off); +} + +#else /* !CONFIG_DYNAMIC_DEBUG */ + +#define dbg(args...) no_printk(args) + +static inline void dbg_print_header(struct sframe_section *sec) {} + +#endif /* !CONFIG_DYNAMIC_DEBUG */ + +#endif /* _SFRAME_DEBUG_H */ --=20 2.48.1