check_preempt_info.c

   1 /*
   2  * Copyright (C) 2021 Oracle.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17
  18 /*
  19  * The preempt_count is a counter as you might guess.  It's incrememented
  20  * if we call a spinlock and decremented when we unlock.  We can hold more
  21  * than one spin lock at a time so at first I thought that we should just
  22  * record "We started this function with a preempt count of zero and took
  23  * two locks so that's a difference of +2 or -2 if we dropped the locks."
  24  * But that didn't work and it turns out more complicated than I imagined.
  25  *
  26  * Locking generally is complicated.  I think printk() was complicated, but
  27  * I didn't really figure out what the issue is.  And then there is also the
  28  * issue of recursion so the lock count got way out of hand.
  29  *
  30  * My approach is to pull out the code that controls the return_states data
  31  * into this function.  Only handle simple things.  Locking functions are
  32  * basically always simple and under 10 lines.  If they take more than one
  33  * spinlock then something complicated is happening so ignore that.
  34  */
  35
  36 #include "smatch.h"
  37 #include "smatch_slist.h"
  38
  39 static int my_id;
  40
  41 STATE(add);
  42 STATE(sub);
  43 STATE(ignore);
  44
  45 struct preempt_info {
  46         const char *name;
  47         int type;
  48 };
  49
  50 static struct preempt_info func_table[] = {
  51         { "preempt_count_add",                  PREEMPT_ADD },
  52         { "__preempt_count_add",                PREEMPT_ADD },
  53         { "local_bh_disable",                   PREEMPT_ADD },
  54         { "spin_lock",                          PREEMPT_ADD },
  55         { "spin_lock_nested",                   PREEMPT_ADD },
  56         { "_spin_lock",                         PREEMPT_ADD },
  57         { "_spin_lock_nested",                  PREEMPT_ADD },
  58         { "__spin_lock",                        PREEMPT_ADD },
  59         { "__spin_lock_nested",                 PREEMPT_ADD },
  60         { "raw_spin_lock",                      PREEMPT_ADD },
  61         { "_raw_spin_lock",                     PREEMPT_ADD },
  62         { "_raw_spin_lock_nested",              PREEMPT_ADD },
  63         { "__raw_spin_lock",                    PREEMPT_ADD },
  64         { "spin_lock_irq",                      PREEMPT_ADD },
  65         { "_spin_lock_irq",                     PREEMPT_ADD },
  66         { "__spin_lock_irq",                    PREEMPT_ADD },
  67         { "_raw_spin_lock_irq",                 PREEMPT_ADD },
  68         { "spin_lock_irqsave",                  PREEMPT_ADD },
  69         { "_spin_lock_irqsave",                 PREEMPT_ADD },
  70         { "__spin_lock_irqsave",                PREEMPT_ADD },
  71         { "_raw_spin_lock_irqsave",             PREEMPT_ADD },
  72         { "__raw_spin_lock_irqsave",            PREEMPT_ADD },
  73         { "spin_lock_irqsave_nested",           PREEMPT_ADD },
  74         { "_spin_lock_irqsave_nested",          PREEMPT_ADD },
  75         { "__spin_lock_irqsave_nested",         PREEMPT_ADD },
  76         { "_raw_spin_lock_irqsave_nested",      PREEMPT_ADD },
  77         { "spin_lock_bh",                       PREEMPT_ADD },
  78         { "_spin_lock_bh",                      PREEMPT_ADD },
  79         { "__spin_lock_bh",                     PREEMPT_ADD },
  80         { "task_rq_lock",                       PREEMPT_ADD },
  81         { "netif_tx_lock_bh",                   PREEMPT_ADD },
  82         { "mt76_tx_status_lock",                PREEMPT_ADD },
  83
  84         { "preempt_count_sub",                  PREEMPT_SUB },
  85         { "__preempt_count_dec_and_test",       PREEMPT_SUB },
  86         { "__preempt_count_sub",                PREEMPT_SUB },
  87         { "local_bh_enable",                    PREEMPT_SUB },
  88         { "__local_bh_enable_ip",               PREEMPT_SUB },
  89         { "spin_unlock",                        PREEMPT_SUB },
  90         { "_spin_unlock",                       PREEMPT_SUB },
  91         { "__spin_unlock",                      PREEMPT_SUB },
  92         { "raw_spin_unlock",                    PREEMPT_SUB },
  93         { "_raw_spin_unlock",                   PREEMPT_SUB },
  94         { "__raw_spin_unlock",                  PREEMPT_SUB },
  95         { "spin_unlock_irq",                    PREEMPT_SUB },
  96         { "_spin_unlock_irq",                   PREEMPT_SUB },
  97         { "__spin_unlock_irq",                  PREEMPT_SUB },
  98         { "_raw_spin_unlock_irq",               PREEMPT_SUB },
  99         { "__raw_spin_unlock_irq",              PREEMPT_SUB },
 100         { "spin_unlock_irqrestore",             PREEMPT_SUB },
 101         { "_spin_unlock_irqrestore",            PREEMPT_SUB },
 102         { "__spin_unlock_irqrestore",           PREEMPT_SUB },
 103         { "_raw_spin_unlock_irqrestore",        PREEMPT_SUB },
 104         { "__raw_spin_unlock_irqrestore",       PREEMPT_SUB },
 105         { "spin_unlock_bh",                     PREEMPT_SUB },
 106         { "_spin_unlock_bh",                    PREEMPT_SUB },
 107         { "__spin_unlock_bh",                   PREEMPT_SUB },
 108         { "task_rq_unlock",                     PREEMPT_SUB },
 109         { "queue_request_and_unlock",           PREEMPT_SUB },
 110         { "netif_tx_unlock_bh",                 PREEMPT_SUB },
 111         { "mt76_tx_status_unlock",              PREEMPT_SUB },
 112 };
 113
 114 static void match_return_info(int return_id, char *return_ranges, struct expression *expr)
 115 {
 116         struct smatch_state *state;
 117
 118         state = get_state(my_id, "preempt", NULL);
 119         if (state != &add && state != &sub)
 120                 return;
 121
 122         sql_insert_return_states(return_id, return_ranges,
 123                         (state == &add) ? PREEMPT_ADD : PREEMPT_SUB,
 124                         -1, "", "");
 125 }
 126
 127 static void preempt_count_add(const char *fn, struct expression *expr, void *_index)
 128 {
 129         struct smatch_state *state;
 130
 131         __preempt_add();
 132
 133         /* If the state is already set then ignore it */
 134         state = get_state(my_id, "preempt", NULL);
 135         if (state)
 136                 set_state(my_id, "preempt", NULL, &ignore);
 137         else
 138                 set_state(my_id, "preempt", NULL, &add);
 139 }
 140
 141 static void preempt_count_sub(const char *fn, struct expression *expr, void *_index)
 142 {
 143         struct smatch_state *state;
 144
 145         __preempt_sub();
 146
 147         /* If the state is already set then ignore it */
 148         state = get_state(my_id, "preempt", NULL);
 149         if (state)
 150                 set_state(my_id, "preempt", NULL, &ignore);
 151         else
 152                 set_state(my_id, "preempt", NULL, &sub);
 153 }
 154
 155 static bool is_preempt_primitive(struct expression *expr)
 156 {
 157         int i;
 158
 159         while (expr->type == EXPR_ASSIGNMENT)
 160                 expr = strip_expr(expr->right);
 161         if (expr->type != EXPR_CALL)
 162                 return false;
 163
 164         if (expr->fn->type != EXPR_SYMBOL)
 165                 return false;
 166
 167         for (i = 0; i < ARRAY_SIZE(func_table); i++) {
 168                 if (sym_name_is(func_table[i].name, expr->fn))
 169                         return true;
 170         }
 171
 172         return false;
 173 }
 174
 175 static void select_return_add(struct expression *expr, int param, char *key, char *value)
 176 {
 177         if (is_preempt_primitive(expr))
 178                 return;
 179         preempt_count_add(NULL, NULL, NULL);
 180 }
 181
 182 static void select_return_sub(struct expression *expr, int param, char *key, char *value)
 183 {
 184         if (is_preempt_primitive(expr))
 185                 return;
 186         preempt_count_sub(NULL, NULL, NULL);
 187 }
 188
 189 void check_preempt_info(int id)
 190 {
 191         int i;
 192
 193         my_id = id;
 194
 195         if (option_project != PROJ_KERNEL)
 196                 return;
 197
 198         for (i = 0; i < ARRAY_SIZE(func_table); i++) {
 199                 if (func_table[i].type == PREEMPT_ADD)
 200                         add_function_hook(func_table[i].name, &preempt_count_add, NULL);
 201                 else
 202                         add_function_hook(func_table[i].name, &preempt_count_sub, NULL);
 203         }
 204
 205         select_return_states_hook(PREEMPT_ADD, &select_return_add);
 206         select_return_states_hook(PREEMPT_SUB, &select_return_sub);
 207
 208         add_split_return_callback(&match_return_info);
 209 }