[7/8] trace: remove limitation on trace point name

  The name of a trace point is provided as a constant string via the
RTE_TRACE_POINT_REGISTER macro.
We can rely on the 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>
---
 lib/eal/common/eal_common_trace.c       | 10 +++-------
 lib/eal/common/eal_common_trace_utils.c |  2 +-
 lib/eal/common/eal_trace.h              |  3 +--
 3 files changed, 5 insertions(+), 10 deletions(-)
  

On Wed, Sep 21, 2022 at 5:35 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 the constant string in the binary and simply point at it.

I am not sure about this. If we compile with -Os (optimized for space)
compiler may decide to use stack instead of rodata.
If so, we will have segfaults with specific compiler or compiler build options.
Thoughts?


> There is then no need for a (fixed size) copy.
>
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
>  lib/eal/common/eal_common_trace.c       | 10 +++-------
>  lib/eal/common/eal_common_trace_utils.c |  2 +-
>  lib/eal/common/eal_trace.h              |  3 +--
>  3 files changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/lib/eal/common/eal_common_trace.c b/lib/eal/common/eal_common_trace.c
> index 5280aa7d62..a2c5a72735 100644
> --- a/lib/eal/common/eal_common_trace.c
> +++ b/lib/eal/common/eal_common_trace.c
> @@ -231,7 +231,7 @@ 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;
> @@ -488,10 +488,7 @@ __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.
> @@ -513,8 +510,7 @@ __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 6340caabbf..9b5a41ca12 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;
>  };
>
> --
> 2.37.3
>
  

On Tue, Oct 11, 2022 at 4:49 PM Jerin Jacob <jerinjacobk@gmail.com> wrote:
>
> On Wed, Sep 21, 2022 at 5:35 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 the constant string in the binary and simply point at it.
>
> I am not sure about this. If we compile with -Os (optimized for space)
> compiler may decide to use stack instead of rodata.
> If so, we will have segfaults with specific compiler or compiler build options.
> Thoughts?

Good point.

We need an explicit storage for the string.
What do you think of:

@@ -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); \
 }
  

On Wed, Oct 12, 2022 at 1:18 PM David Marchand
<david.marchand@redhat.com> wrote:
>
> On Tue, Oct 11, 2022 at 4:49 PM Jerin Jacob <jerinjacobk@gmail.com> wrote:
> >
> > On Wed, Sep 21, 2022 at 5:35 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 the constant string in the binary and simply point at it.
> >
> > I am not sure about this. If we compile with -Os (optimized for space)
> > compiler may decide to use stack instead of rodata.
> > If so, we will have segfaults with specific compiler or compiler build options.
> > Thoughts?
>
> Good point.
>
> We need an explicit storage for the string.
> What do you think of:

This is OK.

> @@ -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); \
>  }
>
>
>
> --
> David Marchand
>