Add ctx_len field to ring buffer context

[lttng-ust.git] / include / lttng / ringbuffer-config.h

diff --git a/include/lttng/ringbuffer-config.h b/include/lttng/ringbuffer-config.h
index 87344c94c8285f94b296f318ae58880dedcc7a39..c95d35cb348d820e69adba599ad3f90b9583b130 100644 (file)
--- a/include/lttng/ringbuffer-config.h
+++ b/include/lttng/ringbuffer-config.h
@@ -228,7 +228,7 @@ struct lttng_ust_lib_ring_buffer_config {
  * removed.
  */
 #define LTTNG_UST_RING_BUFFER_CTX_PADDING      \
-               (24 - sizeof(int) - sizeof(void *))
+               (24 - sizeof(int) - sizeof(void *) - sizeof(void *))
 struct lttng_ust_lib_ring_buffer_ctx {
        /* input received by lib_ring_buffer_reserve(), saved here. */
        struct channel *chan;           /* channel */
@@ -256,9 +256,21 @@ struct lttng_ust_lib_ring_buffer_ctx {
                                         */
        uint64_t tsc;                   /* time-stamp counter value */
        unsigned int rflags;            /* reservation flags */
-       unsigned int padding1;          /* padding to realign on pointer */
+       /*
+        * The field ctx_len is the length of struct
+        * lttng_ust_lib_ring_buffer_ctx as known by the user of
+        * lib_ring_buffer_ctx_init.
+        */
+       unsigned int ctx_len;
        void *ip;                       /* caller ip address */
+       void *priv2;                    /* 2nd priv data */
        char padding2[LTTNG_UST_RING_BUFFER_CTX_PADDING];
+       /*
+        * This is the end of the initial fields expected by the original ABI
+        * between probes and UST. Only the fields above can be used if
+        * ctx_len is 0. Use the value of ctx_len to find out which of the
+        * following fields may be used.
+        */
 };
 
 /**
@@ -274,12 +286,14 @@ static inline lttng_ust_notrace
 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
                              struct channel *chan, void *priv,
                              size_t data_size, int largest_align,
-                             int cpu, struct lttng_ust_shm_handle *handle);
+                             int cpu, struct lttng_ust_shm_handle *handle,
+                             void *priv2);
 static inline
 void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
                              struct channel *chan, void *priv,
                              size_t data_size, int largest_align,
-                             int cpu, struct lttng_ust_shm_handle *handle)
+                             int cpu, struct lttng_ust_shm_handle *handle,
+                             void *priv2)
 {
        ctx->chan = chan;
        ctx->priv = priv;
@@ -288,8 +302,9 @@ void lib_ring_buffer_ctx_init(struct lttng_ust_lib_ring_buffer_ctx *ctx,
        ctx->cpu = cpu;
        ctx->rflags = 0;
        ctx->handle = handle;
-       ctx->padding1 = 0;
+       ctx->ctx_len = sizeof(struct lttng_ust_lib_ring_buffer_ctx);
        ctx->ip = 0;
+       ctx->priv2 = priv2;
        memset(ctx->padding2, 0, LTTNG_UST_RING_BUFFER_CTX_PADDING);
 }