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 // SPDX-License-Identifier: GPL-2.0-only
 #include <linux/objtool.h>
 #include <linux/module.h>
 #include <linux/sort.h>
 #include <asm/ptrace.h>
 #include <asm/stacktrace.h>
 #include <asm/unwind.h>
 #include <asm/orc_types.h>
 #include <asm/orc_lookup.h>
 
 #define orc_warn(fmt, ...) \
     printk_deferred_once(KERN_WARNING "WARNING: " fmt, ##__VA_ARGS__)
 
 #define orc_warn_current(args...)                   \
 ({                                  \
     if (state->task == current && !state->error)            \
         orc_warn(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 bool orc_init __ro_after_init;
 static unsigned int lookup_num_blocks __ro_after_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 unwinder comes across a ftrace trampoline, then find the
  * ftrace function that was used to create it, and use that ftrace
  * function's orc entry, 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 = UNWIND_HINT_TYPE_CALL
 };
 
 /* Fake frame pointer entry -- used as a fallback for generated code */
 static struct orc_entry orc_fp_entry = {
     .type       = UNWIND_HINT_TYPE_CALL,
     .sp_reg     = ORC_REG_BP,
     .sp_offset  = 16,
     .bp_reg     = ORC_REG_PREV_SP,
     .bp_offset  = -16,
     .end        = 0,
 };
 
 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 (is_kernel_inittext(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);
 }
 
 #ifdef CONFIG_MODULES
 
 static DEFINE_MUTEX(sort_mutex);
 static int *cur_orc_ip_table = __start_orc_unwind_ip;
 static struct orc_entry *cur_orc_table = __start_orc_unwind;
 
 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;
 }
 
 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;
     }
 
     /*
      * Note, the orc_unwind and orc_unwind_ip tables were already
      * sorted at build time via the 'sorttable' tool.
      * It's ready for binary search straight away, no need to sort it.
      */
 
     /* 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))
         return true;
 
     return !get_stack_info(addr, state->task, info, &state->stack_mask) &&
         on_stack(info, addr, len);
 }
 
 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 &regs->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) {
         /*
          * As a fallback, try to assume this code uses a frame pointer.
          * This is useful for generated code, like BPF, which ORC
          * doesn't know about.  This is just a guess, so the rest of
          * the unwind is no longer considered reliable.
          */
         orc = &orc_fp_entry;
         state->error = true;
     }
 
     /* 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;
         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_current("missing R10 value at %pB\n",
                      (void *)state->ip);
             goto err;
         }
         break;
 
     case ORC_REG_R13:
         if (!get_reg(state, offsetof(struct pt_regs, r13), &sp)) {
             orc_warn_current("missing R13 value at %pB\n",
                      (void *)state->ip);
             goto err;
         }
         break;
 
     case ORC_REG_DI:
         if (!get_reg(state, offsetof(struct pt_regs, di), &sp)) {
             orc_warn_current("missing RDI value at %pB\n",
                      (void *)state->ip);
             goto err;
         }
         break;
 
     case ORC_REG_DX:
         if (!get_reg(state, offsetof(struct pt_regs, dx), &sp)) {
             orc_warn_current("missing DX value at %pB\n",
                      (void *)state->ip);
             goto err;
         }
         break;
 
     default:
         orc_warn("unknown SP base reg %d at %pB\n",
              orc->sp_reg, (void *)state->ip);
         goto err;
     }
 
     if (indirect) {
         if (!deref_stack_reg(state, sp, &sp))
             goto err;
 
         if (orc->sp_reg == ORC_REG_SP_INDIRECT)
             sp += orc->sp_offset;
     }
 
     /* Find IP, SP and possibly regs: */
     switch (orc->type) {
     case UNWIND_HINT_TYPE_CALL:
         ip_p = sp - sizeof(long);
 
         if (!deref_stack_reg(state, ip_p, &state->ip))
             goto err;
 
         state->ip = unwind_recover_ret_addr(state, state->ip,
                             (unsigned long *)ip_p);
         state->sp = sp;
         state->regs = NULL;
         state->prev_regs = NULL;
         state->signal = false;
         break;
 
     case UNWIND_HINT_TYPE_REGS:
         if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {
             orc_warn_current("can't access registers at %pB\n",
                      (void *)orig_ip);
             goto err;
         }
         /*
          * There is a small chance to interrupt at the entry of
          * arch_rethook_trampoline() where the ORC info doesn't exist.
          * That point is right after the RET to arch_rethook_trampoline()
          * which was modified return address.
          * At that point, the @addr_p of the unwind_recover_rethook()
          * (this has to point the address of the stack entry storing
          * the modified return address) must be "SP - (a stack entry)"
          * because SP is incremented by the RET.
          */
         state->ip = unwind_recover_rethook(state, state->ip,
                 (unsigned long *)(state->sp - sizeof(long)));
         state->regs = (struct pt_regs *)sp;
         state->prev_regs = NULL;
         state->full_regs = true;
         state->signal = true;
         break;
 
     case UNWIND_HINT_TYPE_REGS_PARTIAL:
         if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {
             orc_warn_current("can't access iret registers at %pB\n",
                      (void *)orig_ip);
             goto err;
         }
         /* See UNWIND_HINT_TYPE_REGS case comment. */
         state->ip = unwind_recover_rethook(state, state->ip,
                 (unsigned long *)(state->sp - sizeof(long)));
 
         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 at %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_current("stack going in the wrong direction? at %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 = regs->sp;
         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);

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