# echo 'pid_max:rw-' > ksym_trace_filter
 # cat ksym_trace_filter
 pid_max:rw-
 # echo 'pid_max:ww-' > ksym_trace_filter
 (should return -EINVAL)
 # cat ksym_trace_filter
 (but it ended up removing filter entry)
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NFrederic 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: <4A52E2CE.6080409@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Reading ksym_trace_filter gave me some arbitrary characters,
when it should show nothing. It's because buf is not initialized
when there's no filter.

Also reduce stack usage by about 512 bytes.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NFrederic 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: <4A52E2B4.6030706@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

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: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NFrederic 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: NIngo Molnar <mingo@elte.hu>

ksym_tracer_mutex is declared inside an #ifdef CONFIG_PROFILE_KSYM_TRACER
section. This makes it unavailable for the hardware breakpoint tracer if it is
configured without the breakpoint profiler.

This patch fixes the following build error:

kernel/trace/trace_ksym.c: In function ‘ksym_trace_filter_read’:
kernel/trace/trace_ksym.c:226: erreur: ‘ksym_tracer_mutex’ undeclared (first use in this function)
kernel/trace/trace_ksym.c:226: erreur: (Each undeclared identifier is reported only once
kernel/trace/trace_ksym.c:226: erreur: for each function it appears in.)
kernel/trace/trace_ksym.c: In function ‘ksym_trace_filter_write’:
kernel/trace/trace_ksym.c:273: erreur: ‘ksym_tracer_mutex’ undeclared (first use in this function)
kernel/trace/trace_ksym.c: In function ‘ksym_trace_reset’:
kernel/trace/trace_ksym.c:335: erreur: ‘ksym_tracer_mutex’ undeclared (first use in this function)
make[1]: *** [kernel/trace/trace_ksym.o] Erreur 1

[ Impact: fix a build error ]
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

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