hw-breakpoints: ftrace plugin for kernel symbol tracing using HW Breakpoint interfaces

This patch adds an ftrace plugin to detect and profile memory access over kernel
variables. It uses HW Breakpoint interfaces to 'watch memory addresses.

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 6e735d4771f8..7d5cc37b8fca 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -15,6 +15,10 @@
 #include <linux/trace_seq.h>
 #include <linux/ftrace_event.h>
 
+#ifdef CONFIG_KSYM_TRACER
+#include <asm/hw_breakpoint.h>
+#endif
+
 enum trace_type {
         __TRACE_FIRST_TYPE = 0,
 
@@ -40,6 +44,7 @@ enum trace_type {
         TRACE_KMEM_FREE,
         TRACE_POWER,
         TRACE_BLK,
+        TRACE_KSYM,
 
         __TRACE_LAST_TYPE,
 };
@@ -207,6 +212,21 @@ struct syscall_trace_exit {
         unsigned long           ret;
 };
 
+#define KSYM_SELFTEST_ENTRY "ksym_selftest_dummy"
+extern int process_new_ksym_entry(char *ksymname, int op, unsigned long addr);
+
+struct trace_ksym {
+        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;
+        char                    ksym_name[KSYM_NAME_LEN];
+        char                    p_name[TASK_COMM_LEN];
+};
 
 /*
  * trace_flag_type is an enumeration that holds different
@@ -323,6 +343,7 @@ 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);     \
                 __ftrace_bad_type();                                    \
         } while (0)
 
@@ -540,6 +561,8 @@ extern int trace_selftest_startup_branch(struct tracer *trace,
                                          struct trace_array *tr);
 extern int trace_selftest_startup_hw_branches(struct tracer *trace,
                                               struct trace_array *tr);
+extern int trace_selftest_startup_ksym(struct tracer *trace,
+                                         struct trace_array *tr);
 #endif /* CONFIG_FTRACE_STARTUP_TEST */
 
 extern void *head_page(struct trace_array_cpu *data);