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Subject[PATCH 6/6] dynamic_debug: Add flag for dynamic event tracing
Date
Debugging a specific driver or subsystem can be a lot easier
if we can trace events specific to that driver or subsystem.
This type of filtering can be achieved using existing
dynamic debug library which provides a way to filter based
on files, functions and modules.

Using this, provide an additional flag 'e' to filter event
tracing to specified input.

For example, tracing all IO read/write can be overwhelming
and of no use when debugging a specific driver or a subsystem.
So switch to dynamic event tracing for register accesses.

Example for tracing register accesses in drivers/soc/qcom/*
and the pstore output is given below:

# dyndbg="file drivers/soc/qcom/* +e" trace_event=io tp_pstore
# reboot -f
# mount -t pstore pstore /sys/fs/pstore
# cat /sys/fs/pstore/event-ramoops-0
io_write: type=writel cpu=1 ts:1423596253 data=0xffff00000d2065a4 caller=qcom_smsm_probe+0x524/0x670
io_write: type=writel cpu=1 ts:1423945889 data=0xffff00000d206608 caller=qcom_smsm_probe+0x524/0x670

Note: Tracing is activated only when flag is enabled either
through command line or through dynamic debug control file.

Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
---
include/asm-generic/io-instrumented.h | 28 +++++++++++++++++++++++++--
include/linux/dynamic_debug.h | 1 +
lib/dynamic_debug.c | 1 +
3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/io-instrumented.h b/include/asm-generic/io-instrumented.h
index 7b050e2487ed..023f28571ea3 100644
--- a/include/asm-generic/io-instrumented.h
+++ b/include/asm-generic/io-instrumented.h
@@ -2,6 +2,8 @@
#ifndef _ASM_GENERIC_IO_INSTRUMENTED_H
#define _ASM_GENERIC_IO_INSTRUMENTED_H

+#include <linux/dynamic_debug.h>
+
#if defined(CONFIG_TRACING_EVENTS_IO)
#include <linux/tracepoint-defs.h>

@@ -19,7 +21,7 @@ static inline void do_trace_io_read(const char *type, void *addr) {}
#define __raw_write(v, a, _l) ({ \
volatile void __iomem *_a = (a); \
if (io_tracepoint_active(__tracepoint_io_write)) \
- do_trace_io_write(__stringify(write##_l), (void __force *)(_a));\
+ dynamic_io_write(__stringify(write##_l), (void __force *)(_a)); \
arch_raw_write##_l((v), _a); \
})

@@ -32,7 +34,7 @@ static inline void do_trace_io_read(const char *type, void *addr) {}
_t __a; \
const volatile void __iomem *_a = (a); \
if (io_tracepoint_active(__tracepoint_io_read)) \
- do_trace_io_read(__stringify(read##_l), (void __force *)(_a)); \
+ dynamic_io_read(__stringify(read##_l), (void __force *)(_a)); \
__a = arch_raw_read##_l(_a); \
__a; \
})
@@ -42,4 +44,26 @@ static inline void do_trace_io_read(const char *type, void *addr) {}
#define __raw_readl(a) __raw_read((a), l, u32)
#define __raw_readq(a) __raw_read((a), q, u64)

+#if defined(CONFIG_DYNAMIC_DEBUG) && defined(CONFIG_TRACING_EVENTS_IO)
+#define dynamic_io_write(type, addr) \
+do { \
+ DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, type); \
+ if (unlikely(descriptor.flags & _DPRINTK_FLAGS_EVENT)) \
+ do_trace_io_write(type, addr); \
+} while (0)
+
+#define dynamic_io_read(type, addr) \
+do { \
+ DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, type); \
+ if (unlikely(descriptor.flags & _DPRINTK_FLAGS_EVENT)) \
+ do_trace_io_read(type, addr); \
+} while (0)
+#elif defined(CONFIG_TRACING_EVENTS_IO)
+#define dynamic_io_write(type, addr) do_trace_io_write(type, addr)
+#define dynamic_io_read(type, addr) do_trace_io_read(type, addr)
+#else
+#define dynamic_io_write(type, addr)
+#define dynamic_io_read(type, addr)
+#endif /* CONFIG_DYNAMIC_DEBUG && CONFIG_TRACING_EVENTS_IO */
+
#endif /* _ASM_GENERIC_IO_INSTRUMENTED_H */
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 2fd8006153c3..14e595c51002 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -32,6 +32,7 @@ struct _ddebug {
#define _DPRINTK_FLAGS_INCL_FUNCNAME (1<<2)
#define _DPRINTK_FLAGS_INCL_LINENO (1<<3)
#define _DPRINTK_FLAGS_INCL_TID (1<<4)
+#define _DPRINTK_FLAGS_EVENT (1<<5)
#if defined DEBUG
#define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT
#else
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index c7c96bc7654a..694957a8ae54 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -78,6 +78,7 @@ static inline const char *trim_prefix(const char *path)

static struct { unsigned flag:8; char opt_char; } opt_array[] = {
{ _DPRINTK_FLAGS_PRINT, 'p' },
+ { _DPRINTK_FLAGS_EVENT, 'e' },
{ _DPRINTK_FLAGS_INCL_MODNAME, 'm' },
{ _DPRINTK_FLAGS_INCL_FUNCNAME, 'f' },
{ _DPRINTK_FLAGS_INCL_LINENO, 'l' },
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation
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