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X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: Npa+cYLEtTcnRRD2/fdFqgWfbghjcic7hhW++Xheoitf4XwUrPnHqu4DhOKRugqCM35Xe9S6swRZfyRGs5CDOA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR10MB4430 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-01-30_06,2025-01-30_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 mlxlogscore=999 spamscore=0 phishscore=0 bulkscore=0 malwarescore=0 adultscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2411120000 definitions=main-2501300114 X-Proofpoint-ORIG-GUID: w7W1mpK3yLUOxAcrRKn-6TaKGAb8eq7M X-Proofpoint-GUID: w7W1mpK3yLUOxAcrRKn-6TaKGAb8eq7M On 1/21/25 6:31 PM, Josh Poimboeuf wrote: > 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. > > Signed-off-by: Josh Poimboeuf > --- > include/linux/sframe.h | 5 + > kernel/unwind/sframe.c | 295 ++++++++++++++++++++++++++++++++++- > kernel/unwind/sframe_debug.h | 35 +++++ > 3 files changed, 331 insertions(+), 4 deletions(-) > create mode 100644 kernel/unwind/sframe_debug.h > > diff --git a/include/linux/sframe.h b/include/linux/sframe.h > index ff4b9d1dbd00..2e70085a1e89 100644 > --- a/include/linux/sframe.h > +++ b/include/linux/sframe.h > @@ -3,11 +3,14 @@ > #define _LINUX_SFRAME_H > > #include > +#include > #include > > #ifdef CONFIG_HAVE_UNWIND_USER_SFRAME > > struct sframe_section { > + struct rcu_head rcu; > + > unsigned long sframe_start; > unsigned long sframe_end; > unsigned long text_start; > @@ -28,6 +31,7 @@ extern void sframe_free_mm(struct mm_struct *mm); > 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); > +extern int sframe_find(unsigned long ip, struct unwind_user_frame *frame); > > static inline bool current_has_sframe(void) > { > @@ -42,6 +46,7 @@ static inline bool current_has_sframe(void) > static inline void sframe_free_mm(struct mm_struct *mm) {} > 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; } > +static inline int sframe_find(unsigned long ip, struct unwind_user_frame *frame) { return -ENOSYS; } > static inline bool current_has_sframe(void) { return false; } > > #endif /* CONFIG_HAVE_UNWIND_USER_SFRAME */ > diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c > index fa7d87ffd00a..1a35615a361e 100644 > --- a/kernel/unwind/sframe.c > +++ b/kernel/unwind/sframe.c > @@ -15,9 +15,287 @@ > #include > > #include "sframe.h" > +#include "sframe_debug.h" > > -#define dbg(fmt, ...) \ > - pr_debug("%s (%d): " fmt, current->comm, current->pid, ##__VA_ARGS__) > +struct sframe_fre { > + unsigned int size; > + s32 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_type) > +{ > + if (fre_type > 2) > + return 0; > + return 1 << fre_type; > +} > + > +static __always_inline unsigned char offset_size_enum_to_size(unsigned char 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 *fde) > +{ > + unsigned long fde_addr, ip; > + > + fde_addr = sec->fdes_start + (fde_num * sizeof(struct sframe_fde)); > + unsafe_copy_from_user(fde, (void __user *)fde_addr, > + sizeof(struct sframe_fde), Efault); > + > + ip = sec->sframe_start + fde->start_addr; > + if (ip < sec->text_start || ip > sec->text_end) > + return -EINVAL; > + > + return 0; > + > +Efault: > + return -EFAULT; > +} > + > +static __always_inline int __find_fde(struct sframe_section *sec, > + unsigned long ip, > + struct sframe_fde *fde) > +{ > + s32 ip_off, func_off_low = S32_MIN, func_off_high = S32_MAX; > + struct sframe_fde __user *first, *low, *high, *found = NULL; > + int ret; > + > + ip_off = ip - sec->sframe_start; > + > + first = (void __user *)sec->fdes_start; > + low = first; > + high = first + sec->num_fdes - 1; > + > + while (low <= high) { > + struct sframe_fde __user *mid; > + s32 func_off; > + > + mid = low + ((high - low) / 2); > + > + unsafe_get_user(func_off, (s32 __user *)mid, Efault); > + > + if (ip_off >= func_off) { > + if (func_off < func_off_low) > + return -EFAULT; > + > + func_off_low = func_off; > + > + found = mid; > + low = mid + 1; > + } else { > + if (func_off > func_off_high) > + return -EFAULT; > + > + func_off_high = func_off; > + > + high = mid - 1; > + } > + } > + > + if (!found) > + return -EINVAL; > + > + ret = __read_fde(sec, found - first, fde); > + if (ret) > + return ret; > + > + /* make sure it's not in a gap */ > + if (ip_off < fde->start_addr || ip_off >= fde->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 += sizeof(__to); \ > + to = (typeof(to))__to; \ > +}) > + > +#define UNSAFE_GET_USER_INC(to, from, size, label) \ > +({ \ > + switch (size) { \ > + case 1: \ > + __UNSAFE_GET_USER_INC(to, from, u8, label); \ > + break; \ > + case 2: \ > + __UNSAFE_GET_USER_INC(to, from, u16, label); \ > + break; \ > + case 4: \ > + __UNSAFE_GET_USER_INC(to, from, u32, label); \ > + break; \ > + default: \ > + return -EFAULT; \ > + } \ > +}) > + > +static __always_inline int __read_fre(struct sframe_section *sec, > + struct sframe_fde *fde, > + unsigned long fre_addr, > + struct sframe_fre *fre) > +{ > + unsigned char fde_type = SFRAME_FUNC_FDE_TYPE(fde->info); > + unsigned char fre_type = SFRAME_FUNC_FRE_TYPE(fde->info); > + unsigned char offset_count, offset_size; > + s32 ip_off, cfa_off, ra_off, fp_off; > + unsigned long cur = fre_addr; > + unsigned char addr_size; > + u8 info; > + > + addr_size = 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 == SFRAME_FDE_TYPE_PCINC && ip_off > fde->func_size) > + return -EFAULT; > + > + UNSAFE_GET_USER_INC(info, cur, 1, Efault); > + offset_count = SFRAME_FRE_OFFSET_COUNT(info); > + offset_size = 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 = addr_size + 1 + (offset_count * offset_size); > + > + UNSAFE_GET_USER_INC(cfa_off, cur, offset_size, Efault); > + offset_count--; > + > + ra_off = sec->ra_off; > + if (!ra_off) { > + if (!offset_count--) > + return -EFAULT; > + > + UNSAFE_GET_USER_INC(ra_off, cur, offset_size, Efault); > + } > + > + fp_off = 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 = ip_off; > + fre->cfa_off = cfa_off; > + fre->ra_off = ra_off; > + fre->fp_off = fp_off; > + fre->info = info; > + > + return 0; > + > +Efault: > + return -EFAULT; > +} > + > +static __always_inline int __find_fre(struct sframe_section *sec, > + struct sframe_fde *fde, unsigned long ip, > + struct unwind_user_frame *frame) > +{ > + unsigned char fde_type = SFRAME_FUNC_FDE_TYPE(fde->info); > + struct sframe_fre *fre, *prev_fre = NULL; > + struct sframe_fre fres[2]; > + unsigned long fre_addr; > + bool which = false; > + unsigned int i; > + s32 ip_off; > + > + ip_off = (s32)(ip - sec->sframe_start) - fde->start_addr; > + > + if (fde_type == SFRAME_FDE_TYPE_PCMASK) > + ip_off %= fde->rep_size; > + > + fre_addr = sec->fres_start + fde->fres_off; > + > + for (i = 0; i < fde->fres_num; i++) { > + int ret; > + > + /* > + * Alternate between the two fre_addr[] entries for 'fre' and > + * 'prev_fre'. > + */ > + fre = which ? fres : fres + 1; > + which = !which; > + > + ret = __read_fre(sec, fde, fre_addr, fre); > + if (ret) > + return ret; > + It should be possible to only read the ip_off and info from FRE and defer the reading of offsets (as done in __read_fre) until later when you do need the offsets. See below. We can find the relevant FRE with the following pieces of information: - ip_off - fre_size (this will mean we need to read the uin8_t info in the FRE) > + fre_addr += fre->size; > + > + if (prev_fre && fre->ip_off <= prev_fre->ip_off) > + return -EFAULT; > + > + if (fre->ip_off > ip_off) > + break; > + > + prev_fre = fre; > + } > + > + if (!prev_fre) > + return -EINVAL; > + fre = prev_fre; > + (Invoke the __read_fre here as we know now that this FRE is what we are looking for.) > + frame->cfa_off = fre->cfa_off; > + frame->ra_off = fre->ra_off; > + frame->fp_off = fre->fp_off; > + frame->use_fp = SFRAME_FRE_CFA_BASE_REG_ID(fre->info) == SFRAME_BASE_REG_FP; > + > + return 0; > +}