[DTrace-devel] [PATCH v2 1/5] Add storage offset support in dt_ident_t and dt_idhash_t

[Eugene Loh]

Reviewed-by: Eugene Loh <eugene.loh at oracle.com>


On 11/24/2020 01:50 PM, Kris Van Hees wrote:
> Variables (especially of a complex type) and aggregations will need
> to be allocated from a memory block.  They will therefore require a
> storage offset to be associated with them so that the code generator
> can access the correct memory locations.
>
> The dt_ident_t structure now has a di_offset member to hold the
> storage offset for the identifier (if applicable) and the dt_idhash_t
> structure has a dh_nextoff member to hold the offset to allocate the
> next item at.
>
> The dt_idhash_nextoff(dt_idhash_t *dhp, uint_t alignment, uint_t size)
> function will return the offset where the next data item is to be
> allocated.  The size argument specifies the size (in bytes) of the
> data item.  The returned value is guaranteed to be properly aligned to
> the number of bytes specified by the alignment argument, and the next
> offset member (dh_nextoff in dt_idhash_t) will be advanced by the
> given number of bytes.
>
> Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> ---
>   libdtrace/dt_ident.c | 12 ++++++++++++
>   libdtrace/dt_ident.h |  3 +++
>   2 files changed, 15 insertions(+)
>
> diff --git a/libdtrace/dt_ident.c b/libdtrace/dt_ident.c
> index 392f8e56..34b49728 100644
> --- a/libdtrace/dt_ident.c
> +++ b/libdtrace/dt_ident.c
> @@ -669,6 +669,7 @@ dt_idhash_create(const char *name, const dt_ident_t *tmpl,
>   	dhp->dh_nextid = min;
>   	dhp->dh_minid = min;
>   	dhp->dh_maxid = max;
> +	dhp->dh_nextoff = 0;
>   	dhp->dh_hashsz = _dtrace_strbuckets;
>   
>   	return (dhp);
> @@ -768,6 +769,16 @@ dt_idhash_peekid(dt_idhash_t *dhp)
>   	return dhp->dh_nextid;
>   }
>   
> +uint_t
> +dt_idhash_nextoff(dt_idhash_t *dhp, uint_t alignment, uint_t size)
> +{
> +	uint_t	off = (dhp->dh_nextoff + (alignment - 1)) & ~(alignment - 1);
> +
> +	dhp->dh_nextoff = off + size;
> +
> +	return off;
> +}
> +
>   ulong_t
>   dt_idhash_size(const dt_idhash_t *dhp)
>   {
> @@ -947,6 +958,7 @@ dt_ident_create(const char *name, ushort_t kind, ushort_t flags, uint_t id,
>   	idp->di_data = NULL;
>   	idp->di_ctfp = NULL;
>   	idp->di_type = CTF_ERR;
> +	idp->di_offset = -1;
>   	idp->di_next = NULL;
>   	idp->di_gen = gen;
>   	idp->di_lineno = yylineno;
> diff --git a/libdtrace/dt_ident.h b/libdtrace/dt_ident.h
> index c74aa10c..99f16ad5 100644
> --- a/libdtrace/dt_ident.h
> +++ b/libdtrace/dt_ident.h
> @@ -58,6 +58,7 @@ typedef struct dt_ident {
>   	void *di_data;		/* private data pointer for ops vector */
>   	ctf_file_t *di_ctfp;	/* CTF container for the variable data type */
>   	ctf_id_t di_type;	/* CTF identifier for the variable data type */
> +	int di_offset;		/* storage offset */
>   	struct dt_ident *di_next; /* pointer to next ident in hash chain */
>   	ulong_t di_gen;		/* generation number (pass that created me) */
>   	int di_lineno;		/* line number that defined this identifier */
> @@ -102,6 +103,7 @@ typedef struct dt_idhash {
>   	uint_t dh_nextid;	/* next id to be returned by idhash_nextid() */
>   	uint_t dh_minid;	/* min id to be returned by idhash_nextid() */
>   	uint_t dh_maxid;	/* max id to be returned by idhash_nextid() */
> +	uint_t dh_nextoff;	/* next offset to return at idhash_nextoff() */
>   	ulong_t dh_nelems;	/* number of identifiers in hash table */
>   	ulong_t dh_hashsz;	/* number of entries in dh_buckets array */
>   	dt_ident_t *dh_hash[1];	/* array of hash table bucket pointers */
> @@ -128,6 +130,7 @@ extern void dt_idhash_update(dt_idhash_t *);
>   extern dt_ident_t *dt_idhash_lookup(dt_idhash_t *, const char *);
>   extern int dt_idhash_nextid(dt_idhash_t *, uint_t *);
>   extern uint_t dt_idhash_peekid(dt_idhash_t *);
> +extern uint_t dt_idhash_nextoff(dt_idhash_t *, uint_t, uint_t);
>   extern ulong_t dt_idhash_size(const dt_idhash_t *);
>   extern const char *dt_idhash_name(const dt_idhash_t *);
>