tracing: Add simple expression support to hist triggers
authorTom Zanussi <tom.zanussi@linux.intel.com>
Tue, 16 Jan 2018 02:51:52 +0000 (20:51 -0600)
committerSteven Rostedt (VMware) <rostedt@goodmis.org>
Sat, 10 Mar 2018 21:05:56 +0000 (16:05 -0500)
Add support for simple addition, subtraction, and unary expressions
(-(expr) and expr, where expr = b-a, a+b, a+b+c) to hist triggers, in
order to support a minimal set of useful inter-event calculations.

These operations are needed for calculating latencies between events
(timestamp1-timestamp0) and for combined latencies (latencies over 3
or more events).

In the process, factor out some common code from key and value
parsing.

Link: http://lkml.kernel.org/r/9a9308ead4fe32a433d9c7e95921fb798394f6b2.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
[kbuild test robot fix, add static to parse_atom()]
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
[ Replaced '//' comments with normal /* */ comments ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
kernel/trace/trace_events_hist.c

index a81a709dc703fd746929e25800b85164ebb2055e..4c3c7d784bfd771df023445150b3be9fa3a2f018 100644 (file)
@@ -32,6 +32,13 @@ typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event,
 #define HIST_FIELD_OPERANDS_MAX        2
 #define HIST_FIELDS_MAX                (TRACING_MAP_FIELDS_MAX + TRACING_MAP_VARS_MAX)
 
+enum field_op_id {
+       FIELD_OP_NONE,
+       FIELD_OP_PLUS,
+       FIELD_OP_MINUS,
+       FIELD_OP_UNARY_MINUS,
+};
+
 struct hist_var {
        char                            *name;
        struct hist_trigger_data        *hist_data;
@@ -48,6 +55,8 @@ struct hist_field {
        struct hist_field               *operands[HIST_FIELD_OPERANDS_MAX];
        struct hist_trigger_data        *hist_data;
        struct hist_var                 var;
+       enum field_op_id                operator;
+       char                            *name;
 };
 
 static u64 hist_field_none(struct hist_field *field, void *event,
@@ -98,6 +107,41 @@ static u64 hist_field_log2(struct hist_field *hist_field, void *event,
        return (u64) ilog2(roundup_pow_of_two(val));
 }
 
+static u64 hist_field_plus(struct hist_field *hist_field, void *event,
+                          struct ring_buffer_event *rbe)
+{
+       struct hist_field *operand1 = hist_field->operands[0];
+       struct hist_field *operand2 = hist_field->operands[1];
+
+       u64 val1 = operand1->fn(operand1, event, rbe);
+       u64 val2 = operand2->fn(operand2, event, rbe);
+
+       return val1 + val2;
+}
+
+static u64 hist_field_minus(struct hist_field *hist_field, void *event,
+                           struct ring_buffer_event *rbe)
+{
+       struct hist_field *operand1 = hist_field->operands[0];
+       struct hist_field *operand2 = hist_field->operands[1];
+
+       u64 val1 = operand1->fn(operand1, event, rbe);
+       u64 val2 = operand2->fn(operand2, event, rbe);
+
+       return val1 - val2;
+}
+
+static u64 hist_field_unary_minus(struct hist_field *hist_field, void *event,
+                                 struct ring_buffer_event *rbe)
+{
+       struct hist_field *operand = hist_field->operands[0];
+
+       s64 sval = (s64)operand->fn(operand, event, rbe);
+       u64 val = (u64)-sval;
+
+       return val;
+}
+
 #define DEFINE_HIST_FIELD_FN(type)                                     \
        static u64 hist_field_##type(struct hist_field *hist_field,     \
                                     void *event,                       \
@@ -147,6 +191,7 @@ enum hist_field_flags {
        HIST_FIELD_FL_TIMESTAMP         = 1 << 10,
        HIST_FIELD_FL_TIMESTAMP_USECS   = 1 << 11,
        HIST_FIELD_FL_VAR               = 1 << 12,
+       HIST_FIELD_FL_EXPR              = 1 << 13,
 };
 
 struct var_defs {
@@ -258,6 +303,8 @@ static const char *hist_field_name(struct hist_field *field,
                field_name = hist_field_name(field->operands[0], ++level);
        else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
                field_name = "common_timestamp";
+       else if (field->flags & HIST_FIELD_FL_EXPR)
+               field_name = field->name;
 
        if (field_name == NULL)
                field_name = "";
@@ -519,12 +566,104 @@ static const char *get_hist_field_flags(struct hist_field *hist_field)
        return flags_str;
 }
 
+static void expr_field_str(struct hist_field *field, char *expr)
+{
+       strcat(expr, hist_field_name(field, 0));
+
+       if (field->flags) {
+               const char *flags_str = get_hist_field_flags(field);
+
+               if (flags_str) {
+                       strcat(expr, ".");
+                       strcat(expr, flags_str);
+               }
+       }
+}
+
+static char *expr_str(struct hist_field *field, unsigned int level)
+{
+       char *expr;
+
+       if (level > 1)
+               return NULL;
+
+       expr = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
+       if (!expr)
+               return NULL;
+
+       if (!field->operands[0]) {
+               expr_field_str(field, expr);
+               return expr;
+       }
+
+       if (field->operator == FIELD_OP_UNARY_MINUS) {
+               char *subexpr;
+
+               strcat(expr, "-(");
+               subexpr = expr_str(field->operands[0], ++level);
+               if (!subexpr) {
+                       kfree(expr);
+                       return NULL;
+               }
+               strcat(expr, subexpr);
+               strcat(expr, ")");
+
+               kfree(subexpr);
+
+               return expr;
+       }
+
+       expr_field_str(field->operands[0], expr);
+
+       switch (field->operator) {
+       case FIELD_OP_MINUS:
+               strcat(expr, "-");
+               break;
+       case FIELD_OP_PLUS:
+               strcat(expr, "+");
+               break;
+       default:
+               kfree(expr);
+               return NULL;
+       }
+
+       expr_field_str(field->operands[1], expr);
+
+       return expr;
+}
+
+static int contains_operator(char *str)
+{
+       enum field_op_id field_op = FIELD_OP_NONE;
+       char *op;
+
+       op = strpbrk(str, "+-");
+       if (!op)
+               return FIELD_OP_NONE;
+
+       switch (*op) {
+       case '-':
+               if (*str == '-')
+                       field_op = FIELD_OP_UNARY_MINUS;
+               else
+                       field_op = FIELD_OP_MINUS;
+               break;
+       case '+':
+               field_op = FIELD_OP_PLUS;
+               break;
+       default:
+               break;
+       }
+
+       return field_op;
+}
+
 static void destroy_hist_field(struct hist_field *hist_field,
                               unsigned int level)
 {
        unsigned int i;
 
-       if (level > 2)
+       if (level > 3)
                return;
 
        if (!hist_field)
@@ -534,6 +673,7 @@ static void destroy_hist_field(struct hist_field *hist_field,
                destroy_hist_field(hist_field->operands[i], level + 1);
 
        kfree(hist_field->var.name);
+       kfree(hist_field->name);
 
        kfree(hist_field);
 }
@@ -554,6 +694,9 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
 
        hist_field->hist_data = hist_data;
 
+       if (flags & HIST_FIELD_FL_EXPR)
+               goto out; /* caller will populate */
+
        if (flags & HIST_FIELD_FL_HITCOUNT) {
                hist_field->fn = hist_field_counter;
                goto out;
@@ -626,6 +769,257 @@ static void destroy_hist_fields(struct hist_trigger_data *hist_data)
        }
 }
 
+static struct ftrace_event_field *
+parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
+           char *field_str, unsigned long *flags)
+{
+       struct ftrace_event_field *field = NULL;
+       char *field_name, *modifier, *str;
+
+       modifier = str = kstrdup(field_str, GFP_KERNEL);
+       if (!modifier)
+               return ERR_PTR(-ENOMEM);
+
+       field_name = strsep(&modifier, ".");
+       if (modifier) {
+               if (strcmp(modifier, "hex") == 0)
+                       *flags |= HIST_FIELD_FL_HEX;
+               else if (strcmp(modifier, "sym") == 0)
+                       *flags |= HIST_FIELD_FL_SYM;
+               else if (strcmp(modifier, "sym-offset") == 0)
+                       *flags |= HIST_FIELD_FL_SYM_OFFSET;
+               else if ((strcmp(modifier, "execname") == 0) &&
+                        (strcmp(field_name, "common_pid") == 0))
+                       *flags |= HIST_FIELD_FL_EXECNAME;
+               else if (strcmp(modifier, "syscall") == 0)
+                       *flags |= HIST_FIELD_FL_SYSCALL;
+               else if (strcmp(modifier, "log2") == 0)
+                       *flags |= HIST_FIELD_FL_LOG2;
+               else if (strcmp(modifier, "usecs") == 0)
+                       *flags |= HIST_FIELD_FL_TIMESTAMP_USECS;
+               else {
+                       field = ERR_PTR(-EINVAL);
+                       goto out;
+               }
+       }
+
+       if (strcmp(field_name, "common_timestamp") == 0) {
+               *flags |= HIST_FIELD_FL_TIMESTAMP;
+               hist_data->enable_timestamps = true;
+               if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS)
+                       hist_data->attrs->ts_in_usecs = true;
+       } else {
+               field = trace_find_event_field(file->event_call, field_name);
+               if (!field || !field->size) {
+                       field = ERR_PTR(-EINVAL);
+                       goto out;
+               }
+       }
+ out:
+       kfree(str);
+
+       return field;
+}
+
+static struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
+                                    struct trace_event_file *file, char *str,
+                                    unsigned long *flags, char *var_name)
+{
+       struct ftrace_event_field *field = NULL;
+       struct hist_field *hist_field = NULL;
+       int ret = 0;
+
+       field = parse_field(hist_data, file, str, flags);
+       if (IS_ERR(field)) {
+               ret = PTR_ERR(field);
+               goto out;
+       }
+
+       hist_field = create_hist_field(hist_data, field, *flags, var_name);
+       if (!hist_field) {
+               ret = -ENOMEM;
+               goto out;
+       }
+
+       return hist_field;
+ out:
+       return ERR_PTR(ret);
+}
+
+static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
+                                    struct trace_event_file *file,
+                                    char *str, unsigned long flags,
+                                    char *var_name, unsigned int level);
+
+static struct hist_field *parse_unary(struct hist_trigger_data *hist_data,
+                                     struct trace_event_file *file,
+                                     char *str, unsigned long flags,
+                                     char *var_name, unsigned int level)
+{
+       struct hist_field *operand1, *expr = NULL;
+       unsigned long operand_flags;
+       int ret = 0;
+       char *s;
+
+       /* we support only -(xxx) i.e. explicit parens required */
+
+       if (level > 3) {
+               ret = -EINVAL;
+               goto free;
+       }
+
+       str++; /* skip leading '-' */
+
+       s = strchr(str, '(');
+       if (s)
+               str++;
+       else {
+               ret = -EINVAL;
+               goto free;
+       }
+
+       s = strrchr(str, ')');
+       if (s)
+               *s = '\0';
+       else {
+               ret = -EINVAL; /* no closing ')' */
+               goto free;
+       }
+
+       flags |= HIST_FIELD_FL_EXPR;
+       expr = create_hist_field(hist_data, NULL, flags, var_name);
+       if (!expr) {
+               ret = -ENOMEM;
+               goto free;
+       }
+
+       operand_flags = 0;
+       operand1 = parse_expr(hist_data, file, str, operand_flags, NULL, ++level);
+       if (IS_ERR(operand1)) {
+               ret = PTR_ERR(operand1);
+               goto free;
+       }
+
+       expr->flags |= operand1->flags &
+               (HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);
+       expr->fn = hist_field_unary_minus;
+       expr->operands[0] = operand1;
+       expr->operator = FIELD_OP_UNARY_MINUS;
+       expr->name = expr_str(expr, 0);
+
+       return expr;
+ free:
+       destroy_hist_field(expr, 0);
+       return ERR_PTR(ret);
+}
+
+static int check_expr_operands(struct hist_field *operand1,
+                              struct hist_field *operand2)
+{
+       unsigned long operand1_flags = operand1->flags;
+       unsigned long operand2_flags = operand2->flags;
+
+       if ((operand1_flags & HIST_FIELD_FL_TIMESTAMP_USECS) !=
+           (operand2_flags & HIST_FIELD_FL_TIMESTAMP_USECS))
+               return -EINVAL;
+
+       return 0;
+}
+
+static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
+                                    struct trace_event_file *file,
+                                    char *str, unsigned long flags,
+                                    char *var_name, unsigned int level)
+{
+       struct hist_field *operand1 = NULL, *operand2 = NULL, *expr = NULL;
+       unsigned long operand_flags;
+       int field_op, ret = -EINVAL;
+       char *sep, *operand1_str;
+
+       if (level > 3)
+               return ERR_PTR(-EINVAL);
+
+       field_op = contains_operator(str);
+
+       if (field_op == FIELD_OP_NONE)
+               return parse_atom(hist_data, file, str, &flags, var_name);
+
+       if (field_op == FIELD_OP_UNARY_MINUS)
+               return parse_unary(hist_data, file, str, flags, var_name, ++level);
+
+       switch (field_op) {
+       case FIELD_OP_MINUS:
+               sep = "-";
+               break;
+       case FIELD_OP_PLUS:
+               sep = "+";
+               break;
+       default:
+               goto free;
+       }
+
+       operand1_str = strsep(&str, sep);
+       if (!operand1_str || !str)
+               goto free;
+
+       operand_flags = 0;
+       operand1 = parse_atom(hist_data, file, operand1_str,
+                             &operand_flags, NULL);
+       if (IS_ERR(operand1)) {
+               ret = PTR_ERR(operand1);
+               operand1 = NULL;
+               goto free;
+       }
+
+       /* rest of string could be another expression e.g. b+c in a+b+c */
+       operand_flags = 0;
+       operand2 = parse_expr(hist_data, file, str, operand_flags, NULL, ++level);
+       if (IS_ERR(operand2)) {
+               ret = PTR_ERR(operand2);
+               operand2 = NULL;
+               goto free;
+       }
+
+       ret = check_expr_operands(operand1, operand2);
+       if (ret)
+               goto free;
+
+       flags |= HIST_FIELD_FL_EXPR;
+
+       flags |= operand1->flags &
+               (HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);
+
+       expr = create_hist_field(hist_data, NULL, flags, var_name);
+       if (!expr) {
+               ret = -ENOMEM;
+               goto free;
+       }
+
+       expr->operands[0] = operand1;
+       expr->operands[1] = operand2;
+       expr->operator = field_op;
+       expr->name = expr_str(expr, 0);
+
+       switch (field_op) {
+       case FIELD_OP_MINUS:
+               expr->fn = hist_field_minus;
+               break;
+       case FIELD_OP_PLUS:
+               expr->fn = hist_field_plus;
+               break;
+       default:
+               goto free;
+       }
+
+       return expr;
+ free:
+       destroy_hist_field(operand1, 0);
+       destroy_hist_field(operand2, 0);
+       destroy_hist_field(expr, 0);
+
+       return ERR_PTR(ret);
+}
+
 static int create_hitcount_val(struct hist_trigger_data *hist_data)
 {
        hist_data->fields[HITCOUNT_IDX] =
@@ -648,37 +1042,17 @@ static int __create_val_field(struct hist_trigger_data *hist_data,
                              char *var_name, char *field_str,
                              unsigned long flags)
 {
-       struct ftrace_event_field *field = NULL;
-       char *field_name;
+       struct hist_field *hist_field;
        int ret = 0;
 
-       field_name = strsep(&field_str, ".");
-       if (field_str) {
-               if (strcmp(field_str, "hex") == 0)
-                       flags |= HIST_FIELD_FL_HEX;
-               else {
-                       ret = -EINVAL;
-                       goto out;
-               }
-       }
-
-       if (strcmp(field_name, "common_timestamp") == 0) {
-               flags |= HIST_FIELD_FL_TIMESTAMP;
-               hist_data->enable_timestamps = true;
-       } else {
-               field = trace_find_event_field(file->event_call, field_name);
-               if (!field || !field->size) {
-                       ret = -EINVAL;
-                       goto out;
-               }
-       }
-
-       hist_data->fields[val_idx] = create_hist_field(hist_data, field, flags, var_name);
-       if (!hist_data->fields[val_idx]) {
-               ret = -ENOMEM;
+       hist_field = parse_expr(hist_data, file, field_str, flags, var_name, 0);
+       if (IS_ERR(hist_field)) {
+               ret = PTR_ERR(hist_field);
                goto out;
        }
 
+       hist_data->fields[val_idx] = hist_field;
+
        ++hist_data->n_vals;
        ++hist_data->n_fields;
 
@@ -765,8 +1139,8 @@ static int create_key_field(struct hist_trigger_data *hist_data,
                            struct trace_event_file *file,
                            char *field_str)
 {
-       struct ftrace_event_field *field = NULL;
        struct hist_field *hist_field = NULL;
+
        unsigned long flags = 0;
        unsigned int key_size;
        int ret = 0;
@@ -781,60 +1155,24 @@ static int create_key_field(struct hist_trigger_data *hist_data,
                key_size = sizeof(unsigned long) * HIST_STACKTRACE_DEPTH;
                hist_field = create_hist_field(hist_data, NULL, flags, NULL);
        } else {
-               char *field_name = strsep(&field_str, ".");
-
-               if (field_str) {
-                       if (strcmp(field_str, "hex") == 0)
-                               flags |= HIST_FIELD_FL_HEX;
-                       else if (strcmp(field_str, "sym") == 0)
-                               flags |= HIST_FIELD_FL_SYM;
-                       else if (strcmp(field_str, "sym-offset") == 0)
-                               flags |= HIST_FIELD_FL_SYM_OFFSET;
-                       else if ((strcmp(field_str, "execname") == 0) &&
-                                (strcmp(field_name, "common_pid") == 0))
-                               flags |= HIST_FIELD_FL_EXECNAME;
-                       else if (strcmp(field_str, "syscall") == 0)
-                               flags |= HIST_FIELD_FL_SYSCALL;
-                       else if (strcmp(field_str, "log2") == 0)
-                               flags |= HIST_FIELD_FL_LOG2;
-                       else if (strcmp(field_str, "usecs") == 0)
-                               flags |= HIST_FIELD_FL_TIMESTAMP_USECS;
-                       else {
-                               ret = -EINVAL;
-                               goto out;
-                       }
+               hist_field = parse_expr(hist_data, file, field_str, flags,
+                                       NULL, 0);
+               if (IS_ERR(hist_field)) {
+                       ret = PTR_ERR(hist_field);
+                       goto out;
                }
 
-               if (strcmp(field_name, "common_timestamp") == 0) {
-                       flags |= HIST_FIELD_FL_TIMESTAMP;
-                       hist_data->enable_timestamps = true;
-                       if (flags & HIST_FIELD_FL_TIMESTAMP_USECS)
-                               hist_data->attrs->ts_in_usecs = true;
-                       key_size = sizeof(u64);
-               } else {
-                       field = trace_find_event_field(file->event_call, field_name);
-                       if (!field || !field->size) {
-                               ret = -EINVAL;
-                               goto out;
-                       }
-
-                       if (is_string_field(field))
-                               key_size = MAX_FILTER_STR_VAL;
-                       else
-                               key_size = field->size;
-               }
+               key_size = hist_field->size;
        }
 
-       hist_data->fields[key_idx] = create_hist_field(hist_data, field, flags, NULL);
-       if (!hist_data->fields[key_idx]) {
-               ret = -ENOMEM;
-               goto out;
-       }
+       hist_data->fields[key_idx] = hist_field;
 
        key_size = ALIGN(key_size, sizeof(u64));
        hist_data->fields[key_idx]->size = key_size;
        hist_data->fields[key_idx]->offset = key_offset;
+
        hist_data->key_size += key_size;
+
        if (hist_data->key_size > HIST_KEY_SIZE_MAX) {
                ret = -EINVAL;
                goto out;
@@ -1419,7 +1757,8 @@ hist_trigger_entry_print(struct seq_file *m,
        for (i = 1; i < hist_data->n_vals; i++) {
                field_name = hist_field_name(hist_data->fields[i], 0);
 
-               if (hist_data->fields[i]->flags & HIST_FIELD_FL_VAR)
+               if (hist_data->fields[i]->flags & HIST_FIELD_FL_VAR ||
+                   hist_data->fields[i]->flags & HIST_FIELD_FL_EXPR)
                        continue;
 
                if (hist_data->fields[i]->flags & HIST_FIELD_FL_HEX) {