Fix: context alignment not properly handled

[lttng-ust.git] / liblttng-ust / lttng-context.c

diff --git a/liblttng-ust/lttng-context.c b/liblttng-ust/lttng-context.c
index ecee23445787bce42397e96c200537b1385017ef..6cab7dc1721a57dbbd004cd84f5db4deed32072b 100644 (file)
--- a/liblttng-ust/lttng-context.c
+++ b/liblttng-ust/lttng-context.c
@@ -80,6 +80,7 @@ struct lttng_ctx_field *lttng_append_context(struct lttng_ctx **ctx_p)
                *ctx_p = zmalloc(sizeof(struct lttng_ctx));
                if (!*ctx_p)
                        return NULL;
+               (*ctx_p)->largest_align = 1;
        }
        ctx = *ctx_p;
        if (ctx->nr_fields + 1 > ctx->allocated_fields) {
@@ -99,6 +100,94 @@ struct lttng_ctx_field *lttng_append_context(struct lttng_ctx **ctx_p)
        return field;
 }
 
+/*
+ * lttng_context_update() should be called at least once between context
+ * modification and trace start.
+ */
+void lttng_context_update(struct lttng_ctx *ctx)
+{
+       int i;
+       size_t largest_align = 8;       /* in bits */
+
+       for (i = 0; i < ctx->nr_fields; i++) {
+               struct lttng_type *type;
+               size_t field_align = 8;
+
+               type = &ctx->fields[i].event_field.type;
+               switch (type->atype) {
+               case atype_integer:
+                       field_align = type->u.basic.integer.alignment;
+                       break;
+               case atype_array:
+               {
+                       struct lttng_basic_type *btype;
+
+                       btype = &type->u.array.elem_type;
+                       switch (btype->atype) {
+                       case atype_integer:
+                               field_align = btype->u.basic.integer.alignment;
+                               break;
+                       case atype_string:
+                               break;
+
+                       case atype_array:
+                       case atype_sequence:
+                       default:
+                               WARN_ON_ONCE(1);
+                               break;
+                       }
+                       break;
+               }
+               case atype_sequence:
+               {
+                       struct lttng_basic_type *btype;
+
+                       btype = &type->u.sequence.length_type;
+                       switch (btype->atype) {
+                       case atype_integer:
+                               field_align = btype->u.basic.integer.alignment;
+                               break;
+
+                       case atype_string:
+                       case atype_array:
+                       case atype_sequence:
+                       default:
+                               WARN_ON_ONCE(1);
+                               break;
+                       }
+
+                       btype = &type->u.sequence.elem_type;
+                       switch (btype->atype) {
+                       case atype_integer:
+                               field_align = max_t(size_t,
+                                       field_align,
+                                       btype->u.basic.integer.alignment);
+                               break;
+
+                       case atype_string:
+                               break;
+
+                       case atype_array:
+                       case atype_sequence:
+                       default:
+                               WARN_ON_ONCE(1);
+                               break;
+                       }
+                       break;
+               }
+               case atype_string:
+                       break;
+
+               case atype_enum:
+               default:
+                       WARN_ON_ONCE(1);
+                       break;
+               }
+               largest_align = max_t(size_t, largest_align, field_align);
+       }
+       ctx->largest_align = largest_align >> 3;        /* bits to bytes */
+}
+
 /*
  * Remove last context field.
  */