/* * Copyright (C) 2002-2006 Novell, Inc. * Jan Beulich <jbeulich@novell.com> * This code is released under version 2 of the GNU GPL. * * A simple API for unwinding kernel stacks. This is used for * debugging and error reporting purposes. The kernel doesn't need * full-blown stack unwinding with all the bells and whistles, so there * is not much point in implementing the full Dwarf2 unwind API. */ #include <linux/unwind.h> #include <linux/module.h> #include <linux/delay.h> #include <linux/stop_machine.h> #include <asm/sections.h> #include <asm/uaccess.h> #include <asm/unaligned.h> extern char __start_unwind[], __end_unwind[]; #define MAX_STACK_DEPTH 8 #define EXTRA_INFO(f) { \ BUILD_BUG_ON_ZERO(offsetof(struct unwind_frame_info, f) \ % FIELD_SIZEOF(struct unwind_frame_info, f)) \ + offsetof(struct unwind_frame_info, f) \ / FIELD_SIZEOF(struct unwind_frame_info, f), \ FIELD_SIZEOF(struct unwind_frame_info, f) \ } #define PTREGS_INFO(f) EXTRA_INFO(regs.f) static const struct { unsigned offs:BITS_PER_LONG / 2; unsigned width:BITS_PER_LONG / 2; } reg_info[] = { UNW_REGISTER_INFO }; #undef PTREGS_INFO #undef EXTRA_INFO #ifndef REG_INVALID #define REG_INVALID(r) (reg_info[r].width == 0) #endif #define DW_CFA_nop 0x00 #define DW_CFA_set_loc 0x01 #define DW_CFA_advance_loc1 0x02 #define DW_CFA_advance_loc2 0x03 #define DW_CFA_advance_loc4 0x04 #define DW_CFA_offset_extended 0x05 #define DW_CFA_restore_extended 0x06 #define DW_CFA_undefined 0x07 #define DW_CFA_same_value 0x08 #define DW_CFA_register 0x09 #define DW_CFA_remember_state 0x0a #define DW_CFA_restore_state 0x0b #define DW_CFA_def_cfa 0x0c #define DW_CFA_def_cfa_register 0x0d #define DW_CFA_def_cfa_offset 0x0e #define DW_CFA_def_cfa_expression 0x0f #define DW_CFA_expression 0x10 #define DW_CFA_offset_extended_sf 0x11 #define DW_CFA_def_cfa_sf 0x12 #define DW_CFA_def_cfa_offset_sf 0x13 #define DW_CFA_val_offset 0x14 #define DW_CFA_val_offset_sf 0x15 #define DW_CFA_val_expression 0x16 #define DW_CFA_lo_user 0x1c #define DW_CFA_GNU_window_save 0x2d #define DW_CFA_GNU_args_size 0x2e #define DW_CFA_GNU_negative_offset_extended 0x2f #define DW_CFA_hi_user 0x3f #define DW_EH_PE_FORM 0x07 #define DW_EH_PE_native 0x00 #define DW_EH_PE_leb128 0x01 #define DW_EH_PE_data2 0x02 #define DW_EH_PE_data4 0x03 #define DW_EH_PE_data8 0x04 #define DW_EH_PE_signed 0x08 #define DW_EH_PE_ADJUST 0x70 #define DW_EH_PE_abs 0x00 #define DW_EH_PE_pcrel 0x10 #define DW_EH_PE_textrel 0x20 #define DW_EH_PE_datarel 0x30 #define DW_EH_PE_funcrel 0x40 #define DW_EH_PE_aligned 0x50 #define DW_EH_PE_indirect 0x80 #define DW_EH_PE_omit 0xff typedef unsigned long uleb128_t; typedef signed long sleb128_t; static struct unwind_table { struct { unsigned long pc; unsigned long range; } core, init; const void *address; unsigned long size; struct unwind_table *link; const char *name; } root_table, *last_table; struct unwind_item { enum item_location { Nowhere, Memory, Register, Value } where; uleb128_t value; }; struct unwind_state { uleb128_t loc, org; const u8 *cieStart, *cieEnd; uleb128_t codeAlign; sleb128_t dataAlign; struct cfa { uleb128_t reg, offs; } cfa; struct unwind_item regs[ARRAY_SIZE(reg_info)]; unsigned stackDepth:8; unsigned version:8; const u8 *label; const u8 *stack[MAX_STACK_DEPTH]; }; static const struct cfa badCFA = { ARRAY_SIZE(reg_info), 1 }; static struct unwind_table *find_table(unsigned long pc) { struct unwind_table *table; for (table = &root_table; table; table = table->link) if ((pc >= table->core.pc && pc < table->core.pc + table->core.range) || (pc >= table->init.pc && pc < table->init.pc + table->init.range)) break; return table; } static void init_unwind_table(struct unwind_table *table, const char *name, const void *core_start, unsigned long core_size, const void *init_start, unsigned long init_size, const void *table_start, unsigned long table_size) { table->core.pc = (unsigned long)core_start; table->core.range = core_size; table->init.pc = (unsigned long)init_start; table->init.range = init_size; table->address = table_start; table->size = table_size; table->link = NULL; table->name = name; } void __init unwind_init(void) { init_unwind_table(&root_table, "kernel", _text, _end - _text, NULL, 0, __start_unwind, __end_unwind - __start_unwind); } #ifdef CONFIG_MODULES /* Must be called with module_mutex held. */ void *unwind_add_table(struct module *module, const void *table_start, unsigned long table_size) { struct unwind_table *table; if (table_size <= 0) return NULL; table = kmalloc(sizeof(*table), GFP_KERNEL); if (!table) return NULL; init_unwind_table(table, module->name, module->module_core, module->core_size, module->module_init, module->init_size, table_start, table_size); if (last_table) last_table->link = table; else root_table.link = table; last_table = table; return table; } struct unlink_table_info { struct unwind_table *table; int init_only; }; static int unlink_table(void *arg) { struct unlink_table_info *info = arg; struct unwind_table *table = info->table, *prev; for (prev = &root_table; prev->link && prev->link != table; prev = prev->link) ; if (prev->link) { if (info->init_only) { table->init.pc = 0; table->init.range = 0; info->table = NULL; } else { prev->link = table->link; if (!prev->link) last_table = prev; } } else info->table = NULL; return 0; } /* Must be called with module_mutex held. */ void unwind_remove_table(void *handle, int init_only) { struct unwind_table *table = handle; struct unlink_table_info info; if (!table || table == &root_table) return; if (init_only && table == last_table) { table->init.pc = 0; table->init.range = 0; return; } info.table = table; info.init_only = init_only; stop_machine_run(unlink_table, &info, NR_CPUS); if (info.table) kfree(table); } #endif /* CONFIG_MODULES */ static uleb128_t get_uleb128(const u8 **pcur, const u8 *end) { const u8 *cur = *pcur; uleb128_t value; unsigned shift; for (shift = 0, value = 0; cur < end; shift += 7) { if (shift + 7 > 8 * sizeof(value) && (*cur & 0x7fU) >= (1U << (8 * sizeof(value) - shift))) { cur = end + 1; break; } value |= (uleb128_t)(*cur & 0x7f) << shift; if (!(*cur++ & 0x80)) break; } *pcur = cur; return value; } static sleb128_t get_sleb128(const u8 **pcur, const u8 *end) { const u8 *cur = *pcur; sleb128_t value; unsigned shift; for (shift = 0, value = 0; cur < end; shift += 7) { if (shift + 7 > 8 * sizeof(value) && (*cur & 0x7fU) >= (1U << (8 * sizeof(value) - shift))) { cur = end + 1; break; } value |= (sleb128_t)(*cur & 0x7f) << shift; if (!(*cur & 0x80)) { value |= -(*cur++ & 0x40) << shift; break; } } *pcur = cur; return value; } static unsigned long read_pointer(const u8 **pLoc, const void *end, signed ptrType) { unsigned long value = 0; union { const u8 *p8; const u16 *p16u; const s16 *p16s; const u32 *p32u; const s32 *p32s; const unsigned long *pul; } ptr; if (ptrType < 0 || ptrType == DW_EH_PE_omit) return 0; ptr.p8 = *pLoc; switch(ptrType & DW_EH_PE_FORM) { case DW_EH_PE_data2: if (end < (const void *)(ptr.p16u + 1)) return 0; if(ptrType & DW_EH_PE_signed) value = get_unaligned(ptr.p16s++); else value = get_unaligned(ptr.p16u++); break; case DW_EH_PE_data4: #ifdef CONFIG_64BIT if (end < (const void *)(ptr.p32u + 1)) return 0; if(ptrType & DW_EH_PE_signed) value = get_unaligned(ptr.p32s++); else value = get_unaligned(ptr.p32u++); break; case DW_EH_PE_data8: BUILD_BUG_ON(sizeof(u64) != sizeof(value)); #else BUILD_BUG_ON(sizeof(u32) != sizeof(value)); #endif case DW_EH_PE_native: if (end < (const void *)(ptr.pul + 1)) return 0; value = get_unaligned(ptr.pul++); break; case DW_EH_PE_leb128: BUILD_BUG_ON(sizeof(uleb128_t) > sizeof(value)); value = ptrType & DW_EH_PE_signed ? get_sleb128(&ptr.p8, end) : get_uleb128(&ptr.p8, end); if ((const void *)ptr.p8 > end) return 0; break; default: return 0; } switch(ptrType & DW_EH_PE_ADJUST) { case DW_EH_PE_abs: break; case DW_EH_PE_pcrel: value += (unsigned long)*pLoc; break; default: return 0; } if ((ptrType & DW_EH_PE_indirect) && __get_user(value, (unsigned long *)value)) return 0; *pLoc = ptr.p8; return value; } static signed fde_pointer_type(const u32 *cie) { const u8 *ptr = (const u8 *)(cie + 2); unsigned version = *ptr; if (version != 1) return -1; /* unsupported */ if (*++ptr) { const char *aug; const u8 *end = (const u8 *)(cie + 1) + *cie; uleb128_t len; /* check if augmentation size is first (and thus present) */ if (*ptr != 'z') return -1; /* check if augmentation string is nul-terminated */ if ((ptr = memchr(aug = (const void *)ptr, 0, end - ptr)) == NULL) return -1; ++ptr; /* skip terminator */ get_uleb128(&ptr, end); /* skip code alignment */ get_sleb128(&ptr, end); /* skip data alignment */ /* skip return address column */ version <= 1 ? (void)++ptr : (void)get_uleb128(&ptr, end); len = get_uleb128(&ptr, end); /* augmentation length */ if (ptr + len < ptr || ptr + len > end) return -1; end = ptr + len; while (*++aug) { if (ptr >= end) return -1; switch(*aug) { case 'L': ++ptr; break; case 'P': { signed ptrType = *ptr++; if (!read_pointer(&ptr, end, ptrType) || ptr > end) return -1; } break; case 'R': return *ptr; default: return -1; } } } return DW_EH_PE_native|DW_EH_PE_abs; } static int advance_loc(unsigned long delta, struct unwind_state *state) { state->loc += delta * state->codeAlign; return delta > 0; } static void set_rule(uleb128_t reg, enum item_location where, uleb128_t value, struct unwind_state *state) { if (reg < ARRAY_SIZE(state->regs)) { state->regs[reg].where = where; state->regs[reg].value = value; } } static int processCFI(const u8 *start, const u8 *end, unsigned long targetLoc, signed ptrType, struct unwind_state *state) { union { const u8 *p8; const u16 *p16; const u32 *p32; } ptr; int result = 1; if (start != state->cieStart) { state->loc = state->org; result = processCFI(state->cieStart, state->cieEnd, 0, ptrType, state); if (targetLoc == 0 && state->label == NULL) return result; } for (ptr.p8 = start; result && ptr.p8 < end; ) { switch(*ptr.p8 >> 6) { uleb128_t value; case 0: switch(*ptr.p8++) { case DW_CFA_nop: break; case DW_CFA_set_loc: if ((state->loc = read_pointer(&ptr.p8, end, ptrType)) == 0) result = 0; break; case DW_CFA_advance_loc1: result = ptr.p8 < end && advance_loc(*ptr.p8++, state); break; case DW_CFA_advance_loc2: result = ptr.p8 <= end + 2 && advance_loc(*ptr.p16++, state); break; case DW_CFA_advance_loc4: result = ptr.p8 <= end + 4 && advance_loc(*ptr.p32++, state); break; case DW_CFA_offset_extended: value = get_uleb128(&ptr.p8, end); set_rule(value, Memory, get_uleb128(&ptr.p8, end), state); break; case DW_CFA_val_offset: value = get_uleb128(&ptr.p8, end); set_rule(value, Value, get_uleb128(&ptr.p8, end), state); break; case DW_CFA_offset_extended_sf: value = get_uleb128(&ptr.p8, end); set_rule(value, Memory, get_sleb128(&ptr.p8, end), state); break; case DW_CFA_val_offset_sf: value = get_uleb128(&ptr.p8, end); set_rule(value, Value, get_sleb128(&ptr.p8, end), state); break; case DW_CFA_restore_extended: case DW_CFA_undefined: case DW_CFA_same_value: set_rule(get_uleb128(&ptr.p8, end), Nowhere, 0, state); break; case DW_CFA_register: value = get_uleb128(&ptr.p8, end); set_rule(value, Register, get_uleb128(&ptr.p8, end), state); break; case DW_CFA_remember_state: if (ptr.p8 == state->label) { state->label = NULL; return 1; } if (state->stackDepth >= MAX_STACK_DEPTH) return 0; state->stack[state->stackDepth++] = ptr.p8; break; case DW_CFA_restore_state: if (state->stackDepth) { const uleb128_t loc = state->loc; const u8 *label = state->label; state->label = state->stack[state->stackDepth - 1]; memcpy(&state->cfa, &badCFA, sizeof(state->cfa)); memset(state->regs, 0, sizeof(state->regs)); state->stackDepth = 0; result = processCFI(start, end, 0, ptrType, state); state->loc = loc; state->label = label; } else return 0; break; case DW_CFA_def_cfa: state->cfa.reg = get_uleb128(&ptr.p8, end); /*nobreak*/ case DW_CFA_def_cfa_offset: state->cfa.offs = get_uleb128(&ptr.p8, end); break; case DW_CFA_def_cfa_sf: state->cfa.reg = get_uleb128(&ptr.p8, end); /*nobreak*/ case DW_CFA_def_cfa_offset_sf: state->cfa.offs = get_sleb128(&ptr.p8, end) * state->dataAlign; break; case DW_CFA_def_cfa_register: state->cfa.reg = get_uleb128(&ptr.p8, end); break; /*todo case DW_CFA_def_cfa_expression: */ /*todo case DW_CFA_expression: */ /*todo case DW_CFA_val_expression: */ case DW_CFA_GNU_args_size: get_uleb128(&ptr.p8, end); break; case DW_CFA_GNU_negative_offset_extended: value = get_uleb128(&ptr.p8, end); set_rule(value, Memory, (uleb128_t)0 - get_uleb128(&ptr.p8, end), state); break; case DW_CFA_GNU_window_save: default: result = 0; break; } break; case 1: result = advance_loc(*ptr.p8++ & 0x3f, state); break; case 2: value = *ptr.p8++ & 0x3f; set_rule(value, Memory, get_uleb128(&ptr.p8, end), state); break; case 3: set_rule(*ptr.p8++ & 0x3f, Nowhere, 0, state); break; } if (ptr.p8 > end) result = 0; if (result && targetLoc != 0 && targetLoc < state->loc) return 1; } return result && ptr.p8 == end && (targetLoc == 0 || (/*todo While in theory this should apply, gcc in practice omits everything past the function prolog, and hence the location never reaches the end of the function. targetLoc < state->loc &&*/ state->label == NULL)); } /* Unwind to previous to frame. Returns 0 if successful, negative * number in case of an error. */ int unwind(struct unwind_frame_info *frame) { #define FRAME_REG(r, t) (((t *)frame)[reg_info[r].offs]) const u32 *fde = NULL, *cie = NULL; const u8 *ptr = NULL, *end = NULL; unsigned long startLoc = 0, endLoc = 0, cfa; unsigned i; signed ptrType = -1; uleb128_t retAddrReg = 0; struct unwind_table *table; struct unwind_state state; if (UNW_PC(frame) == 0) return -EINVAL; if ((table = find_table(UNW_PC(frame))) != NULL && !(table->size & (sizeof(*fde) - 1))) { unsigned long tableSize = table->size; for (fde = table->address; tableSize > sizeof(*fde) && tableSize - sizeof(*fde) >= *fde; tableSize -= sizeof(*fde) + *fde, fde += 1 + *fde / sizeof(*fde)) { if (!*fde || (*fde & (sizeof(*fde) - 1))) break; if (!fde[1]) continue; /* this is a CIE */ if ((fde[1] & (sizeof(*fde) - 1)) || fde[1] > (unsigned long)(fde + 1) - (unsigned long)table->address) continue; /* this is not a valid FDE */ cie = fde + 1 - fde[1] / sizeof(*fde); if (*cie <= sizeof(*cie) + 4 || *cie >= fde[1] - sizeof(*fde) || (*cie & (sizeof(*cie) - 1)) || cie[1] || (ptrType = fde_pointer_type(cie)) < 0) { cie = NULL; /* this is not a (valid) CIE */ continue; } ptr = (const u8 *)(fde + 2); startLoc = read_pointer(&ptr, (const u8 *)(fde + 1) + *fde, ptrType); endLoc = startLoc + read_pointer(&ptr, (const u8 *)(fde + 1) + *fde, ptrType & DW_EH_PE_indirect ? ptrType : ptrType & (DW_EH_PE_FORM|DW_EH_PE_signed)); if (UNW_PC(frame) >= startLoc && UNW_PC(frame) < endLoc) break; cie = NULL; } } if (cie != NULL) { memset(&state, 0, sizeof(state)); state.cieEnd = ptr; /* keep here temporarily */ ptr = (const u8 *)(cie + 2); end = (const u8 *)(cie + 1) + *cie; if ((state.version = *ptr) != 1) cie = NULL; /* unsupported version */ else if (*++ptr) { /* check if augmentation size is first (and thus present) */ if (*ptr == 'z') { /* check for ignorable (or already handled) * nul-terminated augmentation string */ while (++ptr < end && *ptr) if (strchr("LPR", *ptr) == NULL) break; } if (ptr >= end || *ptr) cie = NULL; } ++ptr; } if (cie != NULL) { /* get code aligment factor */ state.codeAlign = get_uleb128(&ptr, end); /* get data aligment factor */ state.dataAlign = get_sleb128(&ptr, end); if (state.codeAlign == 0 || state.dataAlign == 0 || ptr >= end) cie = NULL; else { retAddrReg = state.version <= 1 ? *ptr++ : get_uleb128(&ptr, end); /* skip augmentation */ if (((const char *)(cie + 2))[1] == 'z') ptr += get_uleb128(&ptr, end); if (ptr > end || retAddrReg >= ARRAY_SIZE(reg_info) || REG_INVALID(retAddrReg) || reg_info[retAddrReg].width != sizeof(unsigned long)) cie = NULL; } } if (cie != NULL) { state.cieStart = ptr; ptr = state.cieEnd; state.cieEnd = end; end = (const u8 *)(fde + 1) + *fde; /* skip augmentation */ if (((const char *)(cie + 2))[1] == 'z') { uleb128_t augSize = get_uleb128(&ptr, end); if ((ptr += augSize) > end) fde = NULL; } } if (cie == NULL || fde == NULL) { #ifdef CONFIG_FRAME_POINTER unsigned long top, bottom; #endif #ifdef CONFIG_FRAME_POINTER top = STACK_TOP(frame->task); bottom = STACK_BOTTOM(frame->task); # if FRAME_RETADDR_OFFSET < 0 if (UNW_SP(frame) < top && UNW_FP(frame) <= UNW_SP(frame) && bottom < UNW_FP(frame) # else if (UNW_SP(frame) > top && UNW_FP(frame) >= UNW_SP(frame) && bottom > UNW_FP(frame) # endif && !((UNW_SP(frame) | UNW_FP(frame)) & (sizeof(unsigned long) - 1))) { unsigned long link; if (!__get_user(link, (unsigned long *)(UNW_FP(frame) + FRAME_LINK_OFFSET)) # if FRAME_RETADDR_OFFSET < 0 && link > bottom && link < UNW_FP(frame) # else && link > UNW_FP(frame) && link < bottom # endif && !(link & (sizeof(link) - 1)) && !__get_user(UNW_PC(frame), (unsigned long *)(UNW_FP(frame) + FRAME_RETADDR_OFFSET))) { UNW_SP(frame) = UNW_FP(frame) + FRAME_RETADDR_OFFSET # if FRAME_RETADDR_OFFSET < 0 - # else + # endif sizeof(UNW_PC(frame)); UNW_FP(frame) = link; return 0; } } #endif return -ENXIO; } state.org = startLoc; memcpy(&state.cfa, &badCFA, sizeof(state.cfa)); /* process instructions */ if (!processCFI(ptr, end, UNW_PC(frame), ptrType, &state) || state.loc > endLoc || state.regs[retAddrReg].where == Nowhere || state.cfa.reg >= ARRAY_SIZE(reg_info) || reg_info[state.cfa.reg].width != sizeof(unsigned long) || state.cfa.offs % sizeof(unsigned long)) return -EIO; /* update frame */ cfa = FRAME_REG(state.cfa.reg, unsigned long) + state.cfa.offs; startLoc = min((unsigned long)UNW_SP(frame), cfa); endLoc = max((unsigned long)UNW_SP(frame), cfa); if (STACK_LIMIT(startLoc) != STACK_LIMIT(endLoc)) { startLoc = min(STACK_LIMIT(cfa), cfa); endLoc = max(STACK_LIMIT(cfa), cfa); } #ifndef CONFIG_64BIT # define CASES CASE(8); CASE(16); CASE(32) #else # define CASES CASE(8); CASE(16); CASE(32); CASE(64) #endif for (i = 0; i < ARRAY_SIZE(state.regs); ++i) { if (REG_INVALID(i)) { if (state.regs[i].where == Nowhere) continue; return -EIO; } switch(state.regs[i].where) { default: break; case Register: if (state.regs[i].value >= ARRAY_SIZE(reg_info) || REG_INVALID(state.regs[i].value) || reg_info[i].width > reg_info[state.regs[i].value].width) return -EIO; switch(reg_info[state.regs[i].value].width) { #define CASE(n) \ case sizeof(u##n): \ state.regs[i].value = FRAME_REG(state.regs[i].value, \ const u##n); \ break CASES; #undef CASE default: return -EIO; } break; } } for (i = 0; i < ARRAY_SIZE(state.regs); ++i) { if (REG_INVALID(i)) continue; switch(state.regs[i].where) { case Nowhere: if (reg_info[i].width != sizeof(UNW_SP(frame)) || &FRAME_REG(i, __typeof__(UNW_SP(frame))) != &UNW_SP(frame)) continue; UNW_SP(frame) = cfa; break; case Register: switch(reg_info[i].width) { #define CASE(n) case sizeof(u##n): \ FRAME_REG(i, u##n) = state.regs[i].value; \ break CASES; #undef CASE default: return -EIO; } break; case Value: if (reg_info[i].width != sizeof(unsigned long)) return -EIO; FRAME_REG(i, unsigned long) = cfa + state.regs[i].value * state.dataAlign; break; case Memory: { unsigned long addr = cfa + state.regs[i].value * state.dataAlign; if ((state.regs[i].value * state.dataAlign) % sizeof(unsigned long) || addr < startLoc || addr + sizeof(unsigned long) < addr || addr + sizeof(unsigned long) > endLoc) return -EIO; switch(reg_info[i].width) { #define CASE(n) case sizeof(u##n): \ __get_user(FRAME_REG(i, u##n), (u##n *)addr); \ break CASES; #undef CASE default: return -EIO; } } break; } } return 0; #undef CASES #undef FRAME_REG } EXPORT_SYMBOL(unwind); int unwind_init_frame_info(struct unwind_frame_info *info, struct task_struct *tsk, /*const*/ struct pt_regs *regs) { info->task = tsk; arch_unw_init_frame_info(info, regs); return 0; } EXPORT_SYMBOL(unwind_init_frame_info); /* * Prepare to unwind a blocked task. */ int unwind_init_blocked(struct unwind_frame_info *info, struct task_struct *tsk) { info->task = tsk; arch_unw_init_blocked(info); return 0; } EXPORT_SYMBOL(unwind_init_blocked); /* * Prepare to unwind the currently running thread. */ int unwind_init_running(struct unwind_frame_info *info, asmlinkage int (*callback)(struct unwind_frame_info *, void *arg), void *arg) { info->task = current; return arch_unwind_init_running(info, callback, arg); } EXPORT_SYMBOL(unwind_init_running); /* * Unwind until the return pointer is in user-land (or until an error * occurs). Returns 0 if successful, negative number in case of * error. */ int unwind_to_user(struct unwind_frame_info *info) { while (!arch_unw_user_mode(info)) { int err = unwind(info); if (err < 0) return err; } return 0; } EXPORT_SYMBOL(unwind_to_user);