Re: [PATCH] Tracing events with GPIOs

From: Jean-Jacques Hiblot
Date: Tue Dec 17 2013 - 16:00:06 EST

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2013/12/17 Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>:
> (2013/12/17 9:22), Jean-Jacques Hiblot wrote:
>> This patch implements a new tracing mechanism based on kprobes and using GPIO.
>> Debugging with GPIO is very common in the embedded world. At least for those of us
>> fortunate enough to have an oscilloscope or a logic analyzer on their bench...
>> This is especially true if the issue results of a hardware/sofware interaction.
>>
>> Typical use cases are :
>> * mixed software/hardware debugging. For example when the software detects a
>> situation of interest (typically an error) it toggles a GPIO to trigger the
>> oscilloscope acquisition.
>> * direct latency/duration measurements.
>
> Ah, it's interesting to me :)
>
> And I think this feature should be built on the event triggers which
> Tom is working on, instead of kprobes directly, because it allows
> you to take gpio actions on normal tracepoints, and uprobes too :)
>

I'll make a version that uses this framework then. When it's ready
I'll make some measurements to check the overhead of both solutions.

Tom,
is git://git.yoctoproject.org/linux-yocto-contrib
tzanussi/event-triggers-v11 the right starting point ?

Thanks,

Jean-Jacques

> Thank you!
>
>>
>> examples:
>> To trig the oscilloscope whenever a mmc command error:
>> echo "p:my_mmc_blk_error mmc_blk_cmd_error gpiopulse@13" > /sys/kernel/debug/tracing/kprobe_events
>> echo 1 > /sys/kernel/debug/tracing/events/kprobes/my_mmc_blk_error/enable
>>
>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@xxxxxxxxxxxxxxx>
>> ---
>> kernel/trace/Kconfig | 12 ++++
>> kernel/trace/trace_kprobe.c | 167 +++++++++++++++++++++++++++++++++++++++++++-
>> 2 files changed, 177 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
>> index 015f85a..4228768 100644
>> --- a/kernel/trace/Kconfig
>> +++ b/kernel/trace/Kconfig
>> @@ -420,6 +420,18 @@ config KPROBE_EVENT
>> This option is also required by perf-probe subcommand of perf tools.
>> If you want to use perf tools, this option is strongly recommended.
>>
>> +config KPROBE_EVENT_GPIO
>> + depends on KPROBE_EVENT
>> + depends on GPIOLIB
>> + bool "Enable kprobes-based tracing of events via GPIO"
>> + default n
>> + help
>> + This allows the user to use GPIOs as a tracing tool.The primary
>> + purpose of this option is to allow the user to trigger an
>> + oscilloscope on software events.
>> + The GPIO can be set, cleared, toggled, or pulsed when the event
>> + is hit.
>> +
>> config UPROBE_EVENT
>> bool "Enable uprobes-based dynamic events"
>> depends on ARCH_SUPPORTS_UPROBES
>> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
>> index dae9541..5d297f5 100644
>> --- a/kernel/trace/trace_kprobe.c
>> +++ b/kernel/trace/trace_kprobe.c
>> @@ -19,6 +19,7 @@
>>
>> #include <linux/module.h>
>> #include <linux/uaccess.h>
>> +#include <linux/gpio.h>
>>
>> #include "trace_probe.h"
>>
>> @@ -27,6 +28,33 @@
>> /**
>> * Kprobe event core functions
>> */
>> +#ifdef CONFIG_KPROBE_EVENT_GPIO
>> +#define TP_GPIO_UNDEFINED 0
>> +#define TP_GPIO_CMD_SET 1
>> +#define TP_GPIO_CMD_CLEAR 2
>> +#define TP_GPIO_CMD_TOGGLE 3
>> +#define TP_GPIO_CMD_PULSE 4
>> +#define TP_GPIO_CMD_PULSE_HIGH 5
>> +#define TP_GPIO_CMD_PULSE_LOW 6
>> +
>> +static const struct {
>> + const char *name;
>> + int action;
>> +} gpio_actions[] = {
>> + {"gpioset", TP_GPIO_CMD_SET},
>> + {"gpioclear", TP_GPIO_CMD_CLEAR},
>> + {"gpiotoggle", TP_GPIO_CMD_TOGGLE},
>> + {"gpiopulse", TP_GPIO_CMD_PULSE},
>> + {"gpiopulsehigh", TP_GPIO_CMD_PULSE_HIGH},
>> + {"gpiopulselow", TP_GPIO_CMD_PULSE_LOW},
>> +};
>> +
>> +struct gpio_trace {
>> + int gpio;
>> + int action;
>> +};
>> +#endif
>> +
>> struct trace_probe {
>> struct list_head list;
>> struct kretprobe rp; /* Use rp.kp for kprobe use */
>> @@ -38,6 +66,9 @@ struct trace_probe {
>> struct list_head files;
>> ssize_t size; /* trace entry size */
>> unsigned int nr_args;
>> +#ifdef CONFIG_KPROBE_EVENT_GPIO
>> + struct gpio_trace gpio_trace;
>> +#endif
>> struct probe_arg args[];
>> };
>>
>> @@ -164,10 +195,24 @@ error:
>> return ERR_PTR(ret);
>> }
>>
>> +static struct trace_probe *find_gpio_probe(int gpio)
>> +{
>> + struct trace_probe *tp;
>> +
>> + list_for_each_entry(tp, &probe_list, list)
>> + if ((tp->gpio_trace.action) && (tp->gpio_trace.gpio == gpio))
>> + return tp;
>> + return NULL;
>> +}
>> +
>> static void free_trace_probe(struct trace_probe *tp)
>> {
>> int i;
>>
>> +#ifdef CONFIG_KPROBE_EVENT_GPIO
>> + if (tp->gpio_trace.action && !find_gpio_probe(tp->gpio_trace.gpio))
>> + gpio_free(tp->gpio_trace.gpio);
>> +#endif
>> for (i = 0; i < tp->nr_args; i++)
>> traceprobe_free_probe_arg(&tp->args[i]);
>>
>> @@ -435,8 +480,14 @@ static int create_trace_probe(int argc, char **argv)
>> {
>> /*
>> * Argument syntax:
>> - * - Add kprobe: p[:[GRP/]EVENT] [MOD:]KSYM[+OFFS]|KADDR [FETCHARGS]
>> - * - Add kretprobe: r[:[GRP/]EVENT] [MOD:]KSYM[+0] [FETCHARGS]
>> + * - Add kprobe: p[:[GRP/]EVENT] [MOD:]KSYM[+OFFS]|KADDR
>> + * [GPIOACTION@GPIONUM] [FETCHARGS]
>> + * - Add kretprobe: r[:[GRP/]EVENT] [MOD:]KSYM[+0]
>> + * [GPIOACTION@GPIONUM] [FETCHARGS]
>> + * Gpio tracing:
>> + * gpio action can be : gpioset, gpioclear, gpiotoggle, gpiopulse,
>> + * gpiopulsehigh and gpiopulselow
>> + * gpionum is the id of the gpio
>> * Fetch args:
>> * $retval : fetch return value
>> * $stack : fetch stack address
>> @@ -459,6 +510,9 @@ static int create_trace_probe(int argc, char **argv)
>> unsigned long offset = 0;
>> void *addr = NULL;
>> char buf[MAX_EVENT_NAME_LEN];
>> +#ifdef CONFIG_KPROBE_EVENT_GPIO
>> + int len;
>> +#endif
>>
>> /* argc must be >= 1 */
>> if (argv[0][0] == 'p')
>> @@ -541,6 +595,7 @@ static int create_trace_probe(int argc, char **argv)
>> return -EINVAL;
>> }
>> }
>> +
>> argc -= 2; argv += 2;
>>
>> /* setup a probe */
>> @@ -562,6 +617,66 @@ static int create_trace_probe(int argc, char **argv)
>> return PTR_ERR(tp);
>> }
>>
>> +#ifdef CONFIG_KPROBE_EVENT_GPIO
>> + /* parse the optionnal gpio action argument */
>> + for (i = 0; argc && (i < ARRAY_SIZE(gpio_actions)); i++) {
>> + len = strlen(gpio_actions[i].name);
>> + if (strncmp(argv[0], gpio_actions[i].name, len) == 0)
>> + break;
>> + }
>> +
>> + if (argc && (i < ARRAY_SIZE(gpio_actions))) {
>> + int gpio;
>> + unsigned long ul;
>> + int gpio_requested = 0;
>> + ret = -EINVAL;
>> + if (argv[0][len] != '@') {
>> + pr_info("Syntax error. wrong gpio syntax\n");
>> + goto error;
>> + }
>> +
>> + if (kstrtoul(&argv[0][len+1], 0, &ul)) {
>> + pr_info("Failed to parse gpio number.\n");
>> + goto error;
>> + }
>> + gpio = ul;
>> +
>> + if (!gpio_is_valid(gpio)) {
>> + pr_info("gpio %d is not valid.\n", gpio);
>> + goto error;
>> + }
>> +
>> + if (gpio_cansleep(gpio))
>> + pr_info("gpio %d can sleep. This may break your"
>> + "kernel!!!!!!\n", gpio);
>> +
>> + if (!find_gpio_probe(gpio)) {
>> + ret = gpio_request(gpio, event);
>> + if (ret) {
>> + pr_info("can't request gpio %d.\n", gpio);
>> + goto error;
>> + }
>> + gpio_requested = 1;
>> + }
>> +
>> + if ((gpio_actions[i].action == TP_GPIO_CMD_CLEAR) ||
>> + (gpio_actions[i].action == TP_GPIO_CMD_PULSE_LOW))
>> + ret = gpio_direction_output(gpio, 1);
>> + else
>> + ret = gpio_direction_output(gpio, 0);
>> + if (ret) {
>> + pr_info("can't make gpio %d an output.\n", gpio);
>> + if (gpio_requested)
>> + gpio_free(gpio);
>> + goto error;
>> + }
>> +
>> + tp->gpio_trace.gpio = gpio;
>> + tp->gpio_trace.action = gpio_actions[i].action;
>> + argc -= 1; argv += 1;
>> + }
>> +#endif
>> +
>> /* parse arguments */
>> ret = 0;
>> for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
>> @@ -1145,12 +1260,54 @@ kretprobe_perf_func(struct trace_probe *tp, struct kretprobe_instance *ri,
>> }
>> #endif /* CONFIG_PERF_EVENTS */
>>
>> +#ifdef CONFIG_KPROBE_EVENT_GPIO
>> +static __kprobes void kprobe_gpio_take_action(int gpio, int action)
>> +{
>> + int val;
>> + switch (action) {
>> + case TP_GPIO_CMD_PULSE_HIGH:
>> + gpio_set_value(gpio, 1);
>> + /* intentionnaly don't break here */
>> + case TP_GPIO_CMD_CLEAR:
>> + gpio_set_value(gpio, 0);
>> + break;
>> +
>> + case TP_GPIO_CMD_PULSE_LOW:
>> + gpio_set_value(gpio, 0);
>> + /* intentionnaly don't break here */
>> + case TP_GPIO_CMD_SET:
>> + gpio_set_value(gpio, 1);
>> + break;
>> +
>> + case TP_GPIO_CMD_TOGGLE:
>> + val = gpio_get_value(gpio);
>> + gpio_set_value(gpio, val ? 0 : 1);
>> + break;
>> +
>> + case TP_GPIO_CMD_PULSE:
>> + val = gpio_get_value(gpio);
>> + gpio_set_value(gpio, val ? 0 : 1);
>> + gpio_set_value(gpio, val);
>> + break;
>> + }
>> +}
>> +
>> /*
>> * called by perf_trace_init() or __ftrace_set_clr_event() under event_mutex.
>> *
>> * kprobe_trace_self_tests_init() does enable_trace_probe/disable_trace_probe
>> * lockless, but we can't race with this __init function.
>> */
>> +/* Kprobe gpio handler */
>> +static inline __kprobes void kprobe_gpio_func(struct trace_probe *tp,
>> + struct pt_regs *regs)
>> +{
>> + if (tp->gpio_trace.action)
>> + kprobe_gpio_take_action(tp->gpio_trace.gpio,
>> + tp->gpio_trace.action);
>> +}
>> +#endif /* CONFIG_KPROBE_EVENT_GPIO */
>> +
>> static __kprobes
>> int kprobe_register(struct ftrace_event_call *event,
>> enum trace_reg type, void *data)
>> @@ -1186,6 +1343,9 @@ int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs)
>>
>> tp->nhit++;
>>
>> +#ifdef CONFIG_KPROBE_EVENT_GPIO
>> + kprobe_gpio_func(tp, regs);
>> +#endif
>> if (tp->flags & TP_FLAG_TRACE)
>> kprobe_trace_func(tp, regs);
>> #ifdef CONFIG_PERF_EVENTS
>> @@ -1202,6 +1362,9 @@ int kretprobe_dispatcher(struct kretprobe_instance *ri, struct pt_regs *regs)
>>
>> tp->nhit++;
>>
>> +#ifdef CONFIG_KPROBE_EVENT_GPIO
>> + kprobe_gpio_func(tp, regs);
>> +#endif
>> if (tp->flags & TP_FLAG_TRACE)
>> kretprobe_trace_func(tp, ri, regs);
>> #ifdef CONFIG_PERF_EVENTS
>>
>
>
> --
> Masami HIRAMATSU
> IT Management Research Dept. Linux Technology Center
> Hitachi, Ltd., Yokohama Research Laboratory
> E-mail: masami.hiramatsu.pt@xxxxxxxxxxx
>
>
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Next message: Dave Chinner: "Re: [PATCH v4 4/10] xfsprog: xfsio: Add supportFALLOC_FL_COLLAPSE_RANGE for fallocate"
Previous message: Konrad Rzeszutek Wilk: "[PATCH v11 10/12] xen/pvh: Piggyback on PVHVM for grant driver."
In reply to: Masami Hiramatsu: "Re: [PATCH] Tracing events with GPIOs"
Next in thread: Tom Zanussi: "Re: [PATCH] Tracing events with GPIOs"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]