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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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