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    Subject[PATCH v2 04/44] trace/ring_buffer: handle 64bit aligned structs
    Date
    Some 32 bit architectures have 64 bit struct alignment (for example
    Meta which has 64 bit read/write instructions). These require 8 byte
    alignment of event data too, so use CONFIG_HAVE_64BIT_ALIGNED_STRUCT
    instead of CONFIG_64BIT to decide alignment, and align
    buffer_data_page::data accordingly.

    Signed-off-by: James Hogan <james.hogan@imgtec.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    ---
    kernel/trace/ring_buffer.c | 7 +++++--
    1 files changed, 5 insertions(+), 2 deletions(-)

    diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
    index b979426..c4dc029 100644
    --- a/kernel/trace/ring_buffer.c
    +++ b/kernel/trace/ring_buffer.c
    @@ -177,7 +177,8 @@ void tracing_off_permanent(void)
    #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
    #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */

    -#if !defined(CONFIG_64BIT) || defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
    +#if !defined(CONFIG_HAVE_64BIT_ALIGNED_STRUCT) || \
    + defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
    # define RB_FORCE_8BYTE_ALIGNMENT 0
    # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
    #else
    @@ -185,6 +186,8 @@ void tracing_off_permanent(void)
    # define RB_ARCH_ALIGNMENT 8U
    #endif

    +#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
    +
    /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
    #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX

    @@ -333,7 +336,7 @@ EXPORT_SYMBOL_GPL(ring_buffer_event_data);
    struct buffer_data_page {
    u64 time_stamp; /* page time stamp */
    local_t commit; /* write committed index */
    - unsigned char data[]; /* data of buffer page */
    + unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
    };

    /*
    --
    1.7.7.6



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