Re: [PATCH v1 11/12] dyndbg: write debug logs to trace instance

[Łukasz Bartosik]

sob., 4 lis 2023 o 22:49 <jim.cromie@xxxxxxxxx> napisał(a):
>
> On Fri, Nov 3, 2023 at 7:10 AM Łukasz Bartosik <lb@xxxxxxxxxxxx> wrote:
> >
> > When trace is enabled (T flag is set) and trace_dst field is set
> > to value greater than 0 (0 is reserved for trace events) then
> > debug logs will be written to trace instance pointed by trace_dst
> > value, for example when trace_dst value is 2 then debug logs will
> > be written to <debugfs>/tracing/instances/dyndbg_inst_2 instance.
> > Given trace instance will not be initialized until debug logs are
> > requested to be written to it and afer init will persist until
> > reboot.
> >
>
> restating 00 comments -
>
> you can get rid of integer destination ids by adding a new command: open/close
>
> $> echo  \
>  open kms-instance \;\
>  class DRM_UT_KMS -T:kms-instance  # preset-dests-disable-sites \;\
> > /proc/dynamic_debug/control
>

Instead of using above command to preset destination we could preset
destination with open command. I mean last successful
open would preset destination ? What do you think ?

>
> and +T  w/o dest means use existing setting, not just 0 (unless thats
> the existing setting)
>

Sounds good.




> > Signed-off-by: Łukasz Bartosik <lb@xxxxxxxxxxxx>
> > ---
> >  lib/Kconfig.debug   |  1 +
> >  lib/dynamic_debug.c | 79 ++++++++++++++++++++++++++++++++++++++++++---
> >  2 files changed, 76 insertions(+), 4 deletions(-)
> >
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index fa307f93fa2e..9617e92c046d 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -181,6 +181,7 @@ config DYNAMIC_DEBUG_CORE
> >         bool "Enable core function of dynamic debug support"
> >         depends on PRINTK
> >         depends on (DEBUG_FS || PROC_FS)
> > +       depends on TRACING
> >         help
> >           Enable core functional support of dynamic debug. It is useful
> >           when you want to tie dynamic debug to your kernel modules with
> > diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> > index c5cd28e74a02..541d9d522b3b 100644
> > --- a/lib/dynamic_debug.c
> > +++ b/lib/dynamic_debug.c
> > @@ -36,6 +36,7 @@
> >  #include <linux/sched.h>
> >  #include <linux/device.h>
> >  #include <linux/netdevice.h>
> > +#include <linux/trace.h>
> >
> >  #define CREATE_TRACE_POINTS
> >  #include <trace/events/dyndbg.h>
> > @@ -81,6 +82,18 @@ module_param(verbose, int, 0644);
> >  MODULE_PARM_DESC(verbose, " dynamic_debug/control processing "
> >                  "( 0 = off (default), 1 = module add/rm, 2 = >control summary, 3 = parsing, 4 = per-site changes)");
> >
> > +/*
> > + * When trace is enabled (T flag is set) and trace_dst field is set
> > + * to value greater than 0 (0 is reserved for trace events) then
> > + * debug logs will be written to trace instance pointed by trace_dst
> > + * value, for example when trace_dst value is 2 then debug logs will
> > + * be written to <debugfs>/tracing/instances/dyndbg_inst_2 instance.
> > + * Given trace instance will not be initialized until debug logs are
> > + * requested to be written to it and afer init will persist until
> > + * reboot.
> > + */
> > +static struct trace_array *trace_arr[TRACE_DST_MAX];
> > +
> >  static inline struct dd_ctrl *get_ctrl(struct _ddebug *desc)
> >  {
> >         return &desc->ctrl;
> > @@ -255,6 +268,45 @@ static struct ddebug_class_map *ddebug_find_valid_class(struct ddebug_table cons
> >         return NULL;
> >  }
> >
> > +static int handle_trace_dst(struct dd_ctrl *ctrl)
> > +{
> > +#define TRACE_INST_NAME_LEN 16
> > +       char instance_name[TRACE_INST_NAME_LEN];
> > +       struct trace_array *arr;
> > +       int ret = -EINVAL;
> > +
> > +       /* check if trace (T flag) is enabled */
> > +       if (!(ctrl->flags & _DPRINTK_FLAGS_TRACE))
> > +               return 0;
> > +
> > +       /* check if trace destination are trace events */
> > +       if (!ctrl->trace_dst)
> > +               return 0;
> > +
> > +       /* check if trace instance is already set up */
> > +       if (trace_arr[ctrl->trace_dst])
> > +               return 0;
> > +
> > +       snprintf(instance_name, TRACE_INST_NAME_LEN,
> > +                "dyndbg_inst_%u", ctrl->trace_dst);
> > +       arr = trace_array_get_by_name(instance_name);
> > +       if (!arr)
> > +               goto err;
> > +
> > +       ret = trace_array_init_printk(arr);
> > +       if (ret)
> > +               goto err_init;
> > +
> > +       trace_arr[ctrl->trace_dst] = arr;
> > +       return 0;
> > +
> > +err_init:
> > +       trace_array_put(arr);
> > +       trace_array_destroy(arr);
> > +err:
> > +       return ret;
> > +}
> > +
> >  #define __outvar /* filled by callee */
> >  /*
> >   * Search the tables for _ddebug's which match the given `query' and
> > @@ -338,6 +390,9 @@ static int ddebug_change(const struct ddebug_query *query,
> >                         nctrl.trace_dst = modifiers->trace_dst;
> >                         if (!memcmp(&nctrl, get_ctrl(dp), sizeof(nctrl)))
> >                                 continue;
> > +
> > +                       if (handle_trace_dst(&nctrl))
> > +                               continue;
> >  #ifdef CONFIG_JUMP_LABEL
> >                         if (get_flags(dp) & _DPRINTK_FLAGS_ENABLED) {
> >                                 if (!(nctrl.flags & _DPRINTK_FLAGS_ENABLED))
> > @@ -977,8 +1032,8 @@ static DEFINE_PER_CPU(struct ddebug_trace_bufs, ddebug_trace_bufs);
> >  static DEFINE_PER_CPU(int, ddebug_trace_reserve);
> >
> >  __printf(3, 0)
> > -static void ddebug_trace(struct _ddebug *desc, const struct device *dev,
> > -                        const char *fmt, va_list args)
> > +static void ddebug_trace_event(struct _ddebug *desc, const struct device *dev,
> > +                              const char *fmt, va_list args)
> >  {
> >         struct ddebug_trace_buf *buf;
> >         int bufidx;
> > @@ -1010,6 +1065,15 @@ static void ddebug_trace(struct _ddebug *desc, const struct device *dev,
> >         preempt_enable_notrace();
> >  }
> >
> > +__printf(2, 0)
> > +static void ddebug_trace_instance(struct _ddebug *desc, const char *fmt,
> > +                                 va_list *args)
> > +{
> > +       struct va_format vaf = { .fmt = fmt, .va = args};
> > +
> > +       trace_array_printk(trace_arr[get_trace_dst(desc)], _THIS_IP_, "%pV", &vaf);
> > +}
> > +
> >  __printf(2, 3)
> >  static void ddebug_printk(struct _ddebug *desc, const char *fmt, ...)
> >  {
> > @@ -1022,7 +1086,11 @@ static void ddebug_printk(struct _ddebug *desc, const char *fmt, ...)
> >                  * All callers include the KERN_DEBUG prefix to keep the
> >                  * vprintk case simple; strip it out for tracing.
> >                  */
> > -               ddebug_trace(desc, NULL, fmt + strlen(KERN_DEBUG), args);
> > +               if (get_trace_dst(desc))
> > +                       ddebug_trace_instance(desc, fmt, &args);
> > +               else
> > +                       ddebug_trace_event(desc, NULL,
> > +                                          fmt + strlen(KERN_DEBUG), args);
> >                 va_end(args);
> >         }
> >
> > @@ -1044,7 +1112,10 @@ static void ddebug_dev_printk(struct _ddebug *desc, const struct device *dev,
> >                 va_list args;
> >
> >                 va_start(args, fmt);
> > -               ddebug_trace(desc, dev, fmt, args);
> > +               if (get_trace_dst(desc))
> > +                       ddebug_trace_instance(desc, fmt, &args);
> > +               else
> > +                       ddebug_trace_event(desc, dev, fmt, args);
> >                 va_end(args);
> >         }
> >
> > --
> > 2.42.0.869.gea05f2083d-goog
> >