ksym_tracer: Extract trace entry from struct trace_ksym

struct trace_ksym is used as an entry in hbp list, and is also
used as trace_entry stored in ring buffer.

This is not necessary and is a waste of memory in ring buffer.

There is also a bug that dereferencing field->ksym_hbp in
ksym_trace_output() can be invalid.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "K.Prasad" <prasad@linux.vnet.ibm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A52E2A4.4050007@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 22 insertions, 17 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 7d5cc37b8fca..ff1ef411a176 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -215,17 +215,12 @@ struct syscall_trace_exit {
 #define KSYM_SELFTEST_ENTRY "ksym_selftest_dummy"
 extern int process_new_ksym_entry(char *ksymname, int op, unsigned long addr);
 
-struct trace_ksym {
+struct ksym_trace_entry {
         struct trace_entry      ent;
-        struct hw_breakpoint    *ksym_hbp;
-        unsigned long           ksym_addr;
         unsigned long           ip;
-#ifdef CONFIG_PROFILE_KSYM_TRACER
-        unsigned long           counter;
-#endif
-        struct hlist_node       ksym_hlist;
+        unsigned char           type;
         char                    ksym_name[KSYM_NAME_LEN];
-        char                    p_name[TASK_COMM_LEN];
+        char                    cmd[TASK_COMM_LEN];
 };
 
 /*
@@ -343,7 +338,7 @@ extern void __ftrace_bad_type(void);
                           TRACE_SYSCALL_ENTER);                         \
                 IF_ASSIGN(var, ent, struct syscall_trace_exit,          \
                           TRACE_SYSCALL_EXIT);                          \
-                IF_ASSIGN(var, ent, struct trace_ksym, TRACE_KSYM);     \
+                IF_ASSIGN(var, ent, struct ksym_trace_entry, TRACE_KSYM);\
                 __ftrace_bad_type();                                    \
         } while (0)
 
diff --git a/kernel/trace/trace_ksym.c b/kernel/trace/trace_ksym.c
index eef97e7c8db7..085ff055fdfa 100644
--- a/kernel/trace/trace_ksym.c
+++ b/kernel/trace/trace_ksym.c
@@ -37,6 +37,15 @@
 #define KSYM_TRACER_OP_LEN 3 /* rw- */
 #define KSYM_FILTER_ENTRY_LEN (KSYM_NAME_LEN + KSYM_TRACER_OP_LEN + 1)
 
+struct trace_ksym {
+        struct hw_breakpoint    *ksym_hbp;
+        unsigned long           ksym_addr;
+#ifdef CONFIG_PROFILE_KSYM_TRACER
+        unsigned long           counter;
+#endif
+        struct hlist_node       ksym_hlist;
+};
+
 static struct trace_array *ksym_trace_array;
 
 static unsigned int ksym_filter_entry_count;
@@ -71,7 +80,7 @@ void ksym_hbp_handler(struct hw_breakpoint *hbp, struct pt_regs *regs)
 {
         struct ring_buffer_event *event;
         struct trace_array *tr;
-        struct trace_ksym *entry;
+        struct ksym_trace_entry *entry;
         int pc;
 
         if (!ksym_tracing_enabled)
@@ -85,11 +94,12 @@ void ksym_hbp_handler(struct hw_breakpoint *hbp, struct pt_regs *regs)
         if (!event)
                 return;
 
-        entry = ring_buffer_event_data(event);
+        entry           = ring_buffer_event_data(event);
+        entry->ip       = instruction_pointer(regs);
+        entry->type     = hbp->info.type;
         strlcpy(entry->ksym_name, hbp->info.name, KSYM_SYMBOL_LEN);
-        entry->ksym_hbp = hbp;
-        entry->ip = instruction_pointer(regs);
-        strlcpy(entry->p_name, current->comm, TASK_COMM_LEN);
+        strlcpy(entry->cmd, current->comm, TASK_COMM_LEN);
+
 #ifdef CONFIG_PROFILE_KSYM_TRACER
         ksym_collect_stats(hbp->info.address);
 #endif /* CONFIG_PROFILE_KSYM_TRACER */
@@ -380,7 +390,7 @@ static enum print_line_t ksym_trace_output(struct trace_iterator *iter)
 {
         struct trace_entry *entry = iter->ent;
         struct trace_seq *s = &iter->seq;
-        struct trace_ksym *field;
+        struct ksym_trace_entry *field;
         char str[KSYM_SYMBOL_LEN];
         int ret;
 
@@ -389,12 +399,12 @@ static enum print_line_t ksym_trace_output(struct trace_iterator *iter)
 
         trace_assign_type(field, entry);
 
-        ret = trace_seq_printf(s, "%-15s %-5d %-3d %-20s ", field->p_name,
+        ret = trace_seq_printf(s, "%-15s %-5d %-3d %-20s ", field->cmd,
                                 entry->pid, iter->cpu, field->ksym_name);
         if (!ret)
                 return TRACE_TYPE_PARTIAL_LINE;
 
-        switch (field->ksym_hbp->info.type) {
+        switch (field->type) {
         case HW_BREAKPOINT_WRITE:
                 ret = trace_seq_printf(s, " W  ");
                 break;