#include #include #include #include #include #include #include #define orc_warn(fmt, ...) \ printk_deferred_once(KERN_WARNING pr_fmt("WARNING: " fmt), ##__VA_ARGS__) extern int __start_orc_unwind_ip[]; extern int __stop_orc_unwind_ip[]; extern struct orc_entry __start_orc_unwind[]; extern struct orc_entry __stop_orc_unwind[]; static DEFINE_MUTEX(sort_mutex); int *cur_orc_ip_table = __start_orc_unwind_ip; struct orc_entry *cur_orc_table = __start_orc_unwind; unsigned int lookup_num_blocks; bool orc_init; static inline unsigned long orc_ip(const int *ip) { return (unsigned long)ip + *ip; } static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table, unsigned int num_entries, unsigned long ip) { int *first = ip_table; int *last = ip_table + num_entries - 1; int *mid = first, *found = first; if (!num_entries) return NULL; /* * Do a binary range search to find the rightmost duplicate of a given * starting address. Some entries are section terminators which are * "weak" entries for ensuring there are no gaps. They should be * ignored when they conflict with a real entry. */ while (first <= last) { mid = first + ((last - first) / 2); if (orc_ip(mid) <= ip) { found = mid; first = mid + 1; } else last = mid - 1; } return u_table + (found - ip_table); } #ifdef CONFIG_MODULES static struct orc_entry *orc_module_find(unsigned long ip) { struct module *mod; mod = __module_address(ip); if (!mod || !mod->arch.orc_unwind || !mod->arch.orc_unwind_ip) return NULL; return __orc_find(mod->arch.orc_unwind_ip, mod->arch.orc_unwind, mod->arch.num_orcs, ip); } #else static struct orc_entry *orc_module_find(unsigned long ip) { return NULL; } #endif #ifdef CONFIG_DYNAMIC_FTRACE static struct orc_entry *orc_find(unsigned long ip); /* * Ftrace dynamic trampolines do not have orc entries of their own. * But they are copies of the ftrace entries that are static and * defined in ftrace_*.S, which do have orc entries. * * If the undwinder comes across a ftrace trampoline, then find the * ftrace function that was used to create it, and use that ftrace * function's orc entrie, as the placement of the return code in * the stack will be identical. */ static struct orc_entry *orc_ftrace_find(unsigned long ip) { struct ftrace_ops *ops; unsigned long tramp_addr, offset; ops = ftrace_ops_trampoline(ip); if (!ops) return NULL; /* Set tramp_addr to the start of the code copied by the trampoline */ if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) tramp_addr = (unsigned long)ftrace_regs_caller; else tramp_addr = (unsigned long)ftrace_caller; /* Now place tramp_addr to the location within the trampoline ip is at */ offset = ip - ops->trampoline; tramp_addr += offset; /* Prevent unlikely recursion */ if (ip == tramp_addr) return NULL; return orc_find(tramp_addr); } #else static struct orc_entry *orc_ftrace_find(unsigned long ip) { return NULL; } #endif /* * If we crash with IP==0, the last successfully executed instruction * was probably an indirect function call with a NULL function pointer, * and we don't have unwind information for NULL. * This hardcoded ORC entry for IP==0 allows us to unwind from a NULL function * pointer into its parent and then continue normally from there. */ static struct orc_entry null_orc_entry = { .sp_offset = sizeof(long), .sp_reg = ORC_REG_SP, .bp_reg = ORC_REG_UNDEFINED, .type = ORC_TYPE_CALL }; static struct orc_entry *orc_find(unsigned long ip) { static struct orc_entry *orc; if (ip == 0) return &null_orc_entry; /* For non-init vmlinux addresses, use the fast lookup table: */ if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) { unsigned int idx, start, stop; idx = (ip - LOOKUP_START_IP) / LOOKUP_BLOCK_SIZE; if (unlikely((idx >= lookup_num_blocks-1))) { orc_warn("WARNING: bad lookup idx: idx=%u num=%u ip=%pB\n", idx, lookup_num_blocks, (void *)ip); return NULL; } start = orc_lookup[idx]; stop = orc_lookup[idx + 1] + 1; if (unlikely((__start_orc_unwind + start >= __stop_orc_unwind) || (__start_orc_unwind + stop > __stop_orc_unwind))) { orc_warn("WARNING: bad lookup value: idx=%u num=%u start=%u stop=%u ip=%pB\n", idx, lookup_num_blocks, start, stop, (void *)ip); return NULL; } return __orc_find(__start_orc_unwind_ip + start, __start_orc_unwind + start, stop - start, ip); } /* vmlinux .init slow lookup: */ if (init_kernel_text(ip)) return __orc_find(__start_orc_unwind_ip, __start_orc_unwind, __stop_orc_unwind_ip - __start_orc_unwind_ip, ip); /* Module lookup: */ orc = orc_module_find(ip); if (orc) return orc; return orc_ftrace_find(ip); } static void orc_sort_swap(void *_a, void *_b, int size) { struct orc_entry *orc_a, *orc_b; struct orc_entry orc_tmp; int *a = _a, *b = _b, tmp; int delta = _b - _a; /* Swap the .orc_unwind_ip entries: */ tmp = *a; *a = *b + delta; *b = tmp - delta; /* Swap the corresponding .orc_unwind entries: */ orc_a = cur_orc_table + (a - cur_orc_ip_table); orc_b = cur_orc_table + (b - cur_orc_ip_table); orc_tmp = *orc_a; *orc_a = *orc_b; *orc_b = orc_tmp; } static int orc_sort_cmp(const void *_a, const void *_b) { struct orc_entry *orc_a; const int *a = _a, *b = _b; unsigned long a_val = orc_ip(a); unsigned long b_val = orc_ip(b); if (a_val > b_val) return 1; if (a_val < b_val) return -1; /* * The "weak" section terminator entries need to always be on the left * to ensure the lookup code skips them in favor of real entries. * These terminator entries exist to handle any gaps created by * whitelisted .o files which didn't get objtool generation. */ orc_a = cur_orc_table + (a - cur_orc_ip_table); return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1; } #ifdef CONFIG_MODULES void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size, void *_orc, size_t orc_size) { int *orc_ip = _orc_ip; struct orc_entry *orc = _orc; unsigned int num_entries = orc_ip_size / sizeof(int); WARN_ON_ONCE(orc_ip_size % sizeof(int) != 0 || orc_size % sizeof(*orc) != 0 || num_entries != orc_size / sizeof(*orc)); /* * The 'cur_orc_*' globals allow the orc_sort_swap() callback to * associate an .orc_unwind_ip table entry with its corresponding * .orc_unwind entry so they can both be swapped. */ mutex_lock(&sort_mutex); cur_orc_ip_table = orc_ip; cur_orc_table = orc; sort(orc_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap); mutex_unlock(&sort_mutex); mod->arch.orc_unwind_ip = orc_ip; mod->arch.orc_unwind = orc; mod->arch.num_orcs = num_entries; } #endif void __init unwind_init(void) { size_t orc_ip_size = (void *)__stop_orc_unwind_ip - (void *)__start_orc_unwind_ip; size_t orc_size = (void *)__stop_orc_unwind - (void *)__start_orc_unwind; size_t num_entries = orc_ip_size / sizeof(int); struct orc_entry *orc; int i; if (!num_entries || orc_ip_size % sizeof(int) != 0 || orc_size % sizeof(struct orc_entry) != 0 || num_entries != orc_size / sizeof(struct orc_entry)) { orc_warn("WARNING: Bad or missing .orc_unwind table. Disabling unwinder.\n"); return; } /* Sort the .orc_unwind and .orc_unwind_ip tables: */ sort(__start_orc_unwind_ip, num_entries, sizeof(int), orc_sort_cmp, orc_sort_swap); /* Initialize the fast lookup table: */ lookup_num_blocks = orc_lookup_end - orc_lookup; for (i = 0; i < lookup_num_blocks-1; i++) { orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries, LOOKUP_START_IP + (LOOKUP_BLOCK_SIZE * i)); if (!orc) { orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n"); return; } orc_lookup[i] = orc - __start_orc_unwind; } /* Initialize the ending block: */ orc = __orc_find(__start_orc_unwind_ip, __start_orc_unwind, num_entries, LOOKUP_STOP_IP); if (!orc) { orc_warn("WARNING: Corrupt .orc_unwind table. Disabling unwinder.\n"); return; } orc_lookup[lookup_num_blocks-1] = orc - __start_orc_unwind; orc_init = true; } unsigned long unwind_get_return_address(struct unwind_state *state) { if (unwind_done(state)) return 0; return __kernel_text_address(state->ip) ? state->ip : 0; } EXPORT_SYMBOL_GPL(unwind_get_return_address); unsigned long *unwind_get_return_address_ptr(struct unwind_state *state) { if (unwind_done(state)) return NULL; if (state->regs) return &state->regs->ip; if (state->sp) return (unsigned long *)state->sp - 1; return NULL; } static bool stack_access_ok(struct unwind_state *state, unsigned long _addr, size_t len) { struct stack_info *info = &state->stack_info; void *addr = (void *)_addr; if (!on_stack(info, addr, len) && (get_stack_info(addr, state->task, info, &state->stack_mask))) return false; return true; } static bool deref_stack_reg(struct unwind_state *state, unsigned long addr, unsigned long *val) { if (!stack_access_ok(state, addr, sizeof(long))) return false; *val = READ_ONCE_NOCHECK(*(unsigned long *)addr); return true; } static bool deref_stack_regs(struct unwind_state *state, unsigned long addr, unsigned long *ip, unsigned long *sp) { struct pt_regs *regs = (struct pt_regs *)addr; /* x86-32 support will be more complicated due to the ®s->sp hack */ BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_32)); if (!stack_access_ok(state, addr, sizeof(struct pt_regs))) return false; *ip = READ_ONCE_NOCHECK(regs->ip); *sp = READ_ONCE_NOCHECK(regs->sp); return true; } static bool deref_stack_iret_regs(struct unwind_state *state, unsigned long addr, unsigned long *ip, unsigned long *sp) { struct pt_regs *regs = (void *)addr - IRET_FRAME_OFFSET; if (!stack_access_ok(state, addr, IRET_FRAME_SIZE)) return false; *ip = READ_ONCE_NOCHECK(regs->ip); *sp = READ_ONCE_NOCHECK(regs->sp); return true; } /* * If state->regs is non-NULL, and points to a full pt_regs, just get the reg * value from state->regs. * * Otherwise, if state->regs just points to IRET regs, and the previous frame * had full regs, it's safe to get the value from the previous regs. This can * happen when early/late IRQ entry code gets interrupted by an NMI. */ static bool get_reg(struct unwind_state *state, unsigned int reg_off, unsigned long *val) { unsigned int reg = reg_off/8; if (!state->regs) return false; if (state->full_regs) { *val = READ_ONCE_NOCHECK(((unsigned long *)state->regs)[reg]); return true; } if (state->prev_regs) { *val = READ_ONCE_NOCHECK(((unsigned long *)state->prev_regs)[reg]); return true; } return false; } bool unwind_next_frame(struct unwind_state *state) { unsigned long ip_p, sp, tmp, orig_ip = state->ip, prev_sp = state->sp; enum stack_type prev_type = state->stack_info.type; struct orc_entry *orc; bool indirect = false; if (unwind_done(state)) return false; /* Don't let modules unload while we're reading their ORC data. */ preempt_disable(); /* End-of-stack check for user tasks: */ if (state->regs && user_mode(state->regs)) goto the_end; /* * Find the orc_entry associated with the text address. * * For a call frame (as opposed to a signal frame), state->ip points to * the instruction after the call. That instruction's stack layout * could be different from the call instruction's layout, for example * if the call was to a noreturn function. So get the ORC data for the * call instruction itself. */ orc = orc_find(state->signal ? state->ip : state->ip - 1); if (!orc) goto err; /* End-of-stack check for kernel threads: */ if (orc->sp_reg == ORC_REG_UNDEFINED) { if (!orc->end) goto err; goto the_end; } /* Find the previous frame's stack: */ switch (orc->sp_reg) { case ORC_REG_SP: sp = state->sp + orc->sp_offset; break; case ORC_REG_BP: sp = state->bp + orc->sp_offset; break; case ORC_REG_SP_INDIRECT: sp = state->sp + orc->sp_offset; indirect = true; break; case ORC_REG_BP_INDIRECT: sp = state->bp + orc->sp_offset; indirect = true; break; case ORC_REG_R10: if (!get_reg(state, offsetof(struct pt_regs, r10), &sp)) { orc_warn("missing regs for base reg R10 at ip %pB\n", (void *)state->ip); goto err; } break; case ORC_REG_R13: if (!get_reg(state, offsetof(struct pt_regs, r13), &sp)) { orc_warn("missing regs for base reg R13 at ip %pB\n", (void *)state->ip); goto err; } break; case ORC_REG_DI: if (!get_reg(state, offsetof(struct pt_regs, di), &sp)) { orc_warn("missing regs for base reg DI at ip %pB\n", (void *)state->ip); goto err; } break; case ORC_REG_DX: if (!get_reg(state, offsetof(struct pt_regs, dx), &sp)) { orc_warn("missing regs for base reg DX at ip %pB\n", (void *)state->ip); goto err; } break; default: orc_warn("unknown SP base reg %d for ip %pB\n", orc->sp_reg, (void *)state->ip); goto err; } if (indirect) { if (!deref_stack_reg(state, sp, &sp)) goto err; } /* Find IP, SP and possibly regs: */ switch (orc->type) { case ORC_TYPE_CALL: ip_p = sp - sizeof(long); if (!deref_stack_reg(state, ip_p, &state->ip)) goto err; state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, state->ip, (void *)ip_p); state->sp = sp; state->regs = NULL; state->prev_regs = NULL; state->signal = false; break; case ORC_TYPE_REGS: if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) { orc_warn("can't dereference registers at %p for ip %pB\n", (void *)sp, (void *)orig_ip); goto err; } state->regs = (struct pt_regs *)sp; state->prev_regs = NULL; state->full_regs = true; state->signal = true; break; case ORC_TYPE_REGS_IRET: if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) { orc_warn("can't dereference iret registers at %p for ip %pB\n", (void *)sp, (void *)orig_ip); goto err; } if (state->full_regs) state->prev_regs = state->regs; state->regs = (void *)sp - IRET_FRAME_OFFSET; state->full_regs = false; state->signal = true; break; default: orc_warn("unknown .orc_unwind entry type %d for ip %pB\n", orc->type, (void *)orig_ip); goto err; } /* Find BP: */ switch (orc->bp_reg) { case ORC_REG_UNDEFINED: if (get_reg(state, offsetof(struct pt_regs, bp), &tmp)) state->bp = tmp; break; case ORC_REG_PREV_SP: if (!deref_stack_reg(state, sp + orc->bp_offset, &state->bp)) goto err; break; case ORC_REG_BP: if (!deref_stack_reg(state, state->bp + orc->bp_offset, &state->bp)) goto err; break; default: orc_warn("unknown BP base reg %d for ip %pB\n", orc->bp_reg, (void *)orig_ip); goto err; } /* Prevent a recursive loop due to bad ORC data: */ if (state->stack_info.type == prev_type && on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) && state->sp <= prev_sp) { orc_warn("stack going in the wrong direction? ip=%pB\n", (void *)orig_ip); goto err; } preempt_enable(); return true; err: state->error = true; the_end: preempt_enable(); state->stack_info.type = STACK_TYPE_UNKNOWN; return false; } EXPORT_SYMBOL_GPL(unwind_next_frame); void __unwind_start(struct unwind_state *state, struct task_struct *task, struct pt_regs *regs, unsigned long *first_frame) { memset(state, 0, sizeof(*state)); state->task = task; if (!orc_init) goto err; /* * Refuse to unwind the stack of a task while it's executing on another * CPU. This check is racy, but that's ok: the unwinder has other * checks to prevent it from going off the rails. */ if (task_on_another_cpu(task)) goto err; if (regs) { if (user_mode(regs)) goto the_end; state->ip = regs->ip; state->sp = kernel_stack_pointer(regs); state->bp = regs->bp; state->regs = regs; state->full_regs = true; state->signal = true; } else if (task == current) { asm volatile("lea (%%rip), %0\n\t" "mov %%rsp, %1\n\t" "mov %%rbp, %2\n\t" : "=r" (state->ip), "=r" (state->sp), "=r" (state->bp)); } else { struct inactive_task_frame *frame = (void *)task->thread.sp; state->sp = task->thread.sp + sizeof(*frame); state->bp = READ_ONCE_NOCHECK(frame->bp); state->ip = READ_ONCE_NOCHECK(frame->ret_addr); state->signal = (void *)state->ip == ret_from_fork; } if (get_stack_info((unsigned long *)state->sp, state->task, &state->stack_info, &state->stack_mask)) { /* * We weren't on a valid stack. It's possible that * we overflowed a valid stack into a guard page. * See if the next page up is valid so that we can * generate some kind of backtrace if this happens. */ void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp); state->error = true; if (get_stack_info(next_page, state->task, &state->stack_info, &state->stack_mask)) return; } /* * The caller can provide the address of the first frame directly * (first_frame) or indirectly (regs->sp) to indicate which stack frame * to start unwinding at. Skip ahead until we reach it. */ /* When starting from regs, skip the regs frame: */ if (regs) { unwind_next_frame(state); return; } /* Otherwise, skip ahead to the user-specified starting frame: */ while (!unwind_done(state) && (!on_stack(&state->stack_info, first_frame, sizeof(long)) || state->sp < (unsigned long)first_frame)) unwind_next_frame(state); return; err: state->error = true; the_end: state->stack_info.type = STACK_TYPE_UNKNOWN; } EXPORT_SYMBOL_GPL(__unwind_start);