Re: [PATCH v4 08/11] trace: remove limitation on trace point name

[Jerin Jacob <jerinjacobk@gmail.com>]

On Tue, Oct 18, 2022 at 6:58 PM David Marchand
<david.marchand@redhat.com> wrote:
>
> The name of a trace point is provided as a constant string via the
> RTE_TRACE_POINT_REGISTER macro.
> We can rely on an explicit constant string in the binary and simply point
> at it.
> There is then no need for a (fixed size) copy.
>
> Signed-off-by: David Marchand <david.marchand@redhat.com>

Acked-by: Jerin Jacob <jerinj@marvell.com>


> ---
> Changes since v2:
> - stored trace point name in a static variable to make sure the string
>   is put in .data,
>
> ---
>  lib/eal/common/eal_common_trace.c          | 10 +++-------
>  lib/eal/common/eal_common_trace_utils.c    |  2 +-
>  lib/eal/common/eal_trace.h                 |  3 +--
>  lib/eal/include/rte_trace_point_register.h |  3 ++-
>  4 files changed, 7 insertions(+), 11 deletions(-)
>
> diff --git a/lib/eal/common/eal_common_trace.c b/lib/eal/common/eal_common_trace.c
> index ec168e37b3..5caaac8e59 100644
> --- a/lib/eal/common/eal_common_trace.c
> +++ b/lib/eal/common/eal_common_trace.c
> @@ -235,7 +235,7 @@ rte_trace_point_lookup(const char *name)
>                 return NULL;
>
>         STAILQ_FOREACH(tp, &tp_list, next)
> -               if (strncmp(tp->name, name, TRACE_POINT_NAME_SIZE) == 0)
> +               if (strcmp(tp->name, name) == 0)
>                         return tp->handle;
>
>         return NULL;
> @@ -492,10 +492,7 @@ __rte_trace_point_register(rte_trace_point_t *handle, const char *name,
>         }
>
>         /* Initialize the trace point */
> -       if (rte_strscpy(tp->name, name, TRACE_POINT_NAME_SIZE) < 0) {
> -               trace_err("name is too long");
> -               goto free;
> -       }
> +       tp->name = name;
>
>         /* Copy the accumulated fields description and clear it for the next
>          * trace point.
> @@ -517,8 +514,7 @@ __rte_trace_point_register(rte_trace_point_t *handle, const char *name,
>
>         /* All Good !!! */
>         return 0;
> -free:
> -       free(tp);
> +
>  fail:
>         if (trace.register_errno == 0)
>                 trace.register_errno = rte_errno;
> diff --git a/lib/eal/common/eal_common_trace_utils.c b/lib/eal/common/eal_common_trace_utils.c
> index 7bf1c05e12..72108d36a6 100644
> --- a/lib/eal/common/eal_common_trace_utils.c
> +++ b/lib/eal/common/eal_common_trace_utils.c
> @@ -42,7 +42,7 @@ trace_entry_compare(const char *name)
>         int count = 0;
>
>         STAILQ_FOREACH(tp, tp_list, next) {
> -               if (strncmp(tp->name, name, TRACE_POINT_NAME_SIZE) == 0)
> +               if (strcmp(tp->name, name) == 0)
>                         count++;
>                 if (count > 1) {
>                         trace_err("found duplicate entry %s", name);
> diff --git a/lib/eal/common/eal_trace.h b/lib/eal/common/eal_trace.h
> index 72a5a461ae..26a18a2c48 100644
> --- a/lib/eal/common/eal_trace.h
> +++ b/lib/eal/common/eal_trace.h
> @@ -24,14 +24,13 @@
>
>  #define TRACE_PREFIX_LEN 12
>  #define TRACE_DIR_STR_LEN (sizeof("YYYY-mm-dd-AM-HH-MM-SS") + TRACE_PREFIX_LEN)
> -#define TRACE_POINT_NAME_SIZE 64
>  #define TRACE_CTF_MAGIC 0xC1FC1FC1
>  #define TRACE_MAX_ARGS 32
>
>  struct trace_point {
>         STAILQ_ENTRY(trace_point) next;
>         rte_trace_point_t *handle;
> -       char name[TRACE_POINT_NAME_SIZE];
> +       const char *name;
>         char *ctf_field;
>  };
>
> diff --git a/lib/eal/include/rte_trace_point_register.h b/lib/eal/include/rte_trace_point_register.h
> index 2e61439940..a32f4d731b 100644
> --- a/lib/eal/include/rte_trace_point_register.h
> +++ b/lib/eal/include/rte_trace_point_register.h
> @@ -20,9 +20,10 @@ RTE_DECLARE_PER_LCORE(volatile int, trace_point_sz);
>
>  #define RTE_TRACE_POINT_REGISTER(trace, name) \
>  rte_trace_point_t __attribute__((section("__rte_trace_point"))) __##trace; \
> +static const char __##trace##_name[] = RTE_STR(name); \
>  RTE_INIT(trace##_init) \
>  { \
> -       __rte_trace_point_register(&__##trace, RTE_STR(name), \
> +       __rte_trace_point_register(&__##trace, __##trace##_name, \
>                 (void (*)(void)) trace); \
>  }
>
> --
> 2.37.3
>