tracing: Use the return of str_has_prefix() to remove open coded numbers

There are several locations that compare constants to the beginning of
string variables to determine what commands should be done, then the
constant length is used to index into the string. This is error prone as the
hard coded numbers have to match the size of the constants. Instead, use the
len returned from str_has_prefix() and remove the open coded string length
sizes.

Cc: Joe Perches <joe@perches.com>
Acked-by: Masami  Hiramatsu <mhiramat@kernel.org> (for trace_probe part)
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index eac2824a18abef340796bca9d92570b4fdd0bcee..18b86c3974e1ed78ba4550bf78083dd8d751f04e 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4408,13 +4408,15 @@ static int trace_set_options(struct trace_array *tr, char *option)
        int neg = 0;
        int ret;
        size_t orig_len = strlen(option);
+       int len;
 
        cmp = strstrip(option);
 
-       if (str_has_prefix(cmp, "no")) {
+       len = str_has_prefix(cmp, "no");
+       if (len)
                neg = 1;
-               cmp += 2;
-       }
+
+       cmp += len;
 
        mutex_lock(&trace_types_lock);
 

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 541375737403585a428805997f51d2f67c38eebf..9962cb5da8acdebb43e247c1e55df86a19038a51 100644 (file)
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -186,19 +186,20 @@ int traceprobe_parse_event_name(const char **pevent, const char **pgroup,
 static int parse_probe_vars(char *arg, const struct fetch_type *t,
                            struct fetch_insn *code, unsigned int flags)
 {
-       int ret = 0;
        unsigned long param;
+       int ret = 0;
+       int len;
 
        if (strcmp(arg, "retval") == 0) {
                if (flags & TPARG_FL_RETURN)
                        code->op = FETCH_OP_RETVAL;
                else
                        ret = -EINVAL;
-       } else if (str_has_prefix(arg, "stack")) {
-               if (arg[5] == '\0') {
+       } else if ((len = str_has_prefix(arg, "stack"))) {
+               if (arg[len] == '\0') {
                        code->op = FETCH_OP_STACKP;
-               } else if (isdigit(arg[5])) {
-                       ret = kstrtoul(arg + 5, 10, &param);
+               } else if (isdigit(arg[len])) {
+                       ret = kstrtoul(arg + len, 10, &param);
                        if (ret || ((flags & TPARG_FL_KERNEL) &&
                                    param > PARAM_MAX_STACK))
                                ret = -EINVAL;
@@ -213,10 +214,10 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
 #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
        } else if (((flags & TPARG_FL_MASK) ==
                    (TPARG_FL_KERNEL | TPARG_FL_FENTRY)) &&
-                  str_has_prefix(arg, "arg")) {
-               if (!isdigit(arg[3]))
+                  (len = str_has_prefix(arg, "arg"))) {
+               if (!isdigit(arg[len]))
                        return -EINVAL;
-               ret = kstrtoul(arg + 3, 10, &param);
+               ret = kstrtoul(arg + len, 10, &param);
                if (ret || !param || param > PARAM_MAX_STACK)
                        return -EINVAL;
                code->op = FETCH_OP_ARG;

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 3641f28c343f1e3e30490a39f687b12cb65cdb9a..eec648a0d673bed8d8ccc9ff2491ba71d7710871 100644 (file)
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -448,8 +448,10 @@ static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
 
 static __init int enable_stacktrace(char *str)
 {
-       if (str_has_prefix(str, "_filter="))
-               strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE);
+       int len;
+
+       if ((len = str_has_prefix(str, "_filter=")))
+               strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE);
 
        stack_tracer_enabled = 1;
        last_stack_tracer_enabled = 1;