tracing/filters: Enable filtering a cpumask field by another cpumask

The recently introduced ipi_send_cpumask trace event contains a cpumask
field, but it currently cannot be used in filter expressions.

Make event filtering aware of cpumask fields, and allow these to be
filtered by a user-provided cpumask.

The user-provided cpumask is to be given in cpulist format and wrapped as:
"CPUS{$cpulist}". The use of curly braces instead of parentheses is to
prevent predicate_parse() from parsing the contents of CPUS{...} as a
full-fledged predicate subexpression.

This enables e.g.:

$ trace-cmd record -e 'ipi_send_cpumask' -f 'cpumask & CPUS{2,4,6,8-32}'

Link: https://lkml.kernel.org/r/20230707172155.70873-3-vschneid@redhat.com
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Leonardo Bras <leobras@redhat.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index c17623c..1600aeb 100644 (file)
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -808,6 +808,7 @@ enum {
        FILTER_RDYN_STRING,
        FILTER_PTR_STRING,
        FILTER_TRACE_FN,
+       FILTER_CPUMASK,
        FILTER_COMM,
        FILTER_CPU,
        FILTER_STACKTRACE,

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 91fc999..cb1863d 100644 (file)
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -64,6 +64,7 @@ enum filter_pred_fn {
        FILTER_PRED_FN_PCHAR_USER,
        FILTER_PRED_FN_PCHAR,
        FILTER_PRED_FN_CPU,
+       FILTER_PRED_FN_CPUMASK,
        FILTER_PRED_FN_FUNCTION,
        FILTER_PRED_FN_,
        FILTER_PRED_TEST_VISITED,
@@ -71,6 +72,7 @@ enum filter_pred_fn {
 
 struct filter_pred {
        struct regex            *regex;
+       struct cpumask          *mask;
        unsigned short          *ops;
        struct ftrace_event_field *field;
        u64                     val;
@@ -94,6 +96,8 @@ struct filter_pred {
        C(TOO_MANY_OPEN,        "Too many '('"),                        \
        C(TOO_MANY_CLOSE,       "Too few '('"),                         \
        C(MISSING_QUOTE,        "Missing matching quote"),              \
+       C(MISSING_BRACE_OPEN,   "Missing '{'"),                         \
+       C(MISSING_BRACE_CLOSE,  "Missing '}'"),                         \
        C(OPERAND_TOO_LONG,     "Operand too long"),                    \
        C(EXPECT_STRING,        "Expecting string field"),              \
        C(EXPECT_DIGIT,         "Expecting numeric field"),             \
@@ -103,6 +107,7 @@ struct filter_pred {
        C(BAD_SUBSYS_FILTER,    "Couldn't find or set field in one of a subsystem's events"), \
        C(TOO_MANY_PREDS,       "Too many terms in predicate expression"), \
        C(INVALID_FILTER,       "Meaningless filter expression"),       \
+       C(INVALID_CPULIST,      "Invalid cpulist"),     \
        C(IP_FIELD_ONLY,        "Only 'ip' field is supported for function trace"), \
        C(INVALID_VALUE,        "Invalid value (did you forget quotes)?"), \
        C(NO_FUNCTION,          "Function not found"),                  \
@@ -190,6 +195,7 @@ static void free_predicate(struct filter_pred *pred)
 {
        if (pred) {
                kfree(pred->regex);
+               kfree(pred->mask);
                kfree(pred);
        }
 }
@@ -877,6 +883,26 @@ static int filter_pred_cpu(struct filter_pred *pred, void *event)
        }
 }
 
+/* Filter predicate for cpumask field vs user-provided cpumask */
+static int filter_pred_cpumask(struct filter_pred *pred, void *event)
+{
+       u32 item = *(u32 *)(event + pred->offset);
+       int loc = item & 0xffff;
+       const struct cpumask *mask = (event + loc);
+       const struct cpumask *cmp = pred->mask;
+
+       switch (pred->op) {
+       case OP_EQ:
+               return cpumask_equal(mask, cmp);
+       case OP_NE:
+               return !cpumask_equal(mask, cmp);
+       case OP_BAND:
+               return cpumask_intersects(mask, cmp);
+       default:
+               return 0;
+       }
+}
+
 /* Filter predicate for COMM. */
 static int filter_pred_comm(struct filter_pred *pred, void *event)
 {
@@ -1244,8 +1270,12 @@ static void filter_free_subsystem_filters(struct trace_subsystem_dir *dir,
 
 int filter_assign_type(const char *type)
 {
-       if (strstr(type, "__data_loc") && strstr(type, "char"))
-               return FILTER_DYN_STRING;
+       if (strstr(type, "__data_loc")) {
+               if (strstr(type, "char"))
+                       return FILTER_DYN_STRING;
+               if (strstr(type, "cpumask_t"))
+                       return FILTER_CPUMASK;
+               }
 
        if (strstr(type, "__rel_loc") && strstr(type, "char"))
                return FILTER_RDYN_STRING;
@@ -1357,6 +1387,8 @@ static int filter_pred_fn_call(struct filter_pred *pred, void *event)
                return filter_pred_pchar(pred, event);
        case FILTER_PRED_FN_CPU:
                return filter_pred_cpu(pred, event);
+       case FILTER_PRED_FN_CPUMASK:
+               return filter_pred_cpumask(pred, event);
        case FILTER_PRED_FN_FUNCTION:
                return filter_pred_function(pred, event);
        case FILTER_PRED_TEST_VISITED:
@@ -1568,6 +1600,67 @@ static int parse_pred(const char *str, void *data,
                strncpy(pred->regex->pattern, str + s, len);
                pred->regex->pattern[len] = 0;
 
+       } else if (!strncmp(str + i, "CPUS", 4)) {
+               unsigned int maskstart;
+               char *tmp;
+
+               switch (field->filter_type) {
+               case FILTER_CPUMASK:
+                       break;
+               default:
+                       parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, pos + i);
+                       goto err_free;
+               }
+
+               switch (op) {
+               case OP_EQ:
+               case OP_NE:
+               case OP_BAND:
+                       break;
+               default:
+                       parse_error(pe, FILT_ERR_ILLEGAL_FIELD_OP, pos + i);
+                       goto err_free;
+               }
+
+               /* Skip CPUS */
+               i += 4;
+               if (str[i++] != '{') {
+                       parse_error(pe, FILT_ERR_MISSING_BRACE_OPEN, pos + i);
+                       goto err_free;
+               }
+               maskstart = i;
+
+               /* Walk the cpulist until closing } */
+               for (; str[i] && str[i] != '}'; i++);
+               if (str[i] != '}') {
+                       parse_error(pe, FILT_ERR_MISSING_BRACE_CLOSE, pos + i);
+                       goto err_free;
+               }
+
+               if (maskstart == i) {
+                       parse_error(pe, FILT_ERR_INVALID_CPULIST, pos + i);
+                       goto err_free;
+               }
+
+               /* Copy the cpulist between { and } */
+               tmp = kmalloc((i - maskstart) + 1, GFP_KERNEL);
+               strscpy(tmp, str + maskstart, (i - maskstart) + 1);
+
+               pred->mask = kzalloc(cpumask_size(), GFP_KERNEL);
+               if (!pred->mask)
+                       goto err_mem;
+
+               /* Now parse it */
+               if (cpulist_parse(tmp, pred->mask)) {
+                       parse_error(pe, FILT_ERR_INVALID_CPULIST, pos + i);
+                       goto err_free;
+               }
+
+               /* Move along */
+               i++;
+               if (field->filter_type == FILTER_CPUMASK)
+                       pred->fn_num = FILTER_PRED_FN_CPUMASK;
+
        /* This is either a string, or an integer */
        } else if (str[i] == '\'' || str[i] == '"') {
                char q = str[i];