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Date: Sat, 4 Nov 2023 15:48:55 -0600
From: jim.cromie@...il.com
To: Łukasz Bartosik <lb@...ihalf.com>
Cc: Jason Baron <jbaron@...mai.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>,
Douglas Anderson <dianders@...omium.org>,
Guenter Roeck <groeck@...gle.com>,
Yaniv Tzoreff <yanivt@...gle.com>,
Benson Leung <bleung@...gle.com>,
Steven Rostedt <rostedt@...dmis.org>,
Vincent Whitchurch <vincent.whitchurch@...s.com>,
Pekka Paalanen <ppaalanen@...il.com>,
Sean Paul <seanpaul@...omium.org>,
Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org,
upstream@...ihalf.com
Subject: Re: [PATCH v1 11/12] dyndbg: write debug logs to trace instance
On Fri, Nov 3, 2023 at 7:10 AM Łukasz Bartosik <lb@...ihalf.com> 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
echo "class DRM_UT_KMS +T # enable sites, with the preselected data" >
/proc/dynamic_debug/control
open - assign name to id, reserve it, hide it from user
+T:valid-name # fail command if name wasnt opened
and +T w/o dest means use existing setting, not just 0 (unless thats
the existing setting)
> Signed-off-by: Łukasz Bartosik <lb@...ihalf.com>
> ---
> 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
>
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