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Date: Wed, 12 May 2010 13:02:26 +0200
From: Frederic Weisbecker <fweisbec@...il.com>
To: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Masami Hiramatsu <mhiramat@...hat.com>,
Randy Dunlap <rdunlap@...otime.net>,
Ananth N Mavinakayanahalli <ananth@...ibm.com>,
Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
"Frank Ch. Eigler" <fche@...hat.com>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 11/11] Uprobes traceevents patch.
On Wed, Mar 31, 2010 at 09:23:11PM +0530, Srikar Dronamraju wrote:
> Uprobes Trace_events interface
>
> The following patch implements trace_event support for uprobes. In its
> current form it can be used to put probes at a specified text address
> in a process and dump the required registers when the code flow reaches
> the probed address.
>
> This is based on trace_events for kprobes to the extent that it may
> resemble that file on 2.6.34-rc3.
>
> The following example shows how to dump the instruction pointer and %ax a
> register at the probed text address.
>
> Start a process to trace. Get the address to trace.
> [Here pid is asssumed as 3548]
> [Address to trace is 0x0000000000446420]
> [Registers to be dumped are %ip and %ax]
>
> # cd /sys/kernel/debug/tracing/
> # echo 'p 3548:0x0000000000446420 %ip %ax' > uprobe_events
> # cat uprobe_events
> p:uprobes/p_3548_0x0000000000446420 3548:0x0000000000446420 %ip=%ip %ax=%ax
> # cat events/uprobes/p_3548_0x0000000000446420/enable
> 0
> [enable the event]
> # echo 1 > events/uprobes/p_3548_0x0000000000446420/enable
> # cat events/uprobes/p_3548_0x0000000000446420/enable
> 1
> # #### do some activity on the program so that it hits the breakpoint
> # cat uprobe_profile
> 3548 p_3548_0x0000000000446420 234
> # head trace
> # tracer: nop
> #
> # TASK-PID CPU# TIMESTAMP FUNCTION
> # | | | | |
> zsh-3548 [001] 294.285812: p_3548_0x0000000000446420: (0x446420) %ip=446421 %ax=1
> zsh-3548 [001] 294.285884: p_3548_0x0000000000446420: (0x446420) %ip=446421 %ax=1
> zsh-3548 [001] 294.285894: p_3548_0x0000000000446420: (0x446420) %ip=446421 %ax=1
> zsh-3548 [001] 294.285903: p_3548_0x0000000000446420: (0x446420) %ip=446421 %ax=1
> zsh-3548 [001] 294.285912: p_3548_0x0000000000446420: (0x446420) %ip=446421 %ax=1
> zsh-3548 [001] 294.285922: p_3548_0x0000000000446420: (0x446420) %ip=446421 %ax=1
>
> TODO: Documentation/trace/uprobetrace.txt
>
> Signed-off-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> ---
>
> kernel/trace/Kconfig | 8
> kernel/trace/Makefile | 1
> kernel/trace/trace.h | 12 +
> kernel/trace/trace_uprobe.c | 926 +++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 947 insertions(+), 0 deletions(-)
> create mode 100644 kernel/trace/trace_uprobe.c
>
>
> diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
> index 13e13d4..1435e09 100644
> --- a/kernel/trace/Kconfig
> +++ b/kernel/trace/Kconfig
> @@ -557,6 +557,14 @@ config RING_BUFFER_BENCHMARK
>
> If unsure, say N.
>
> +config UPROBE_EVENT
> + depends on UPROBES
> + bool "Enable uprobes-based dynamic events"
> + select TRACING
> + default y
> + help
> + This allows the user to add tracing events (similar to tracepoints)
> + on the fly via the traceevents interface.
That doesn't explain much what it does. Please explain its goal of
creating a trace event on top of a userspace dynamic probe.
> +#define MAX_TRACE_ARGS 128
> +#define MAX_ARGSTR_LEN 63
> +#define MAX_EVENT_NAME_LEN 64
This can be shared with kprobes in a new kernel/trace/dyn_probes.h
or something.
> +const char *ureserved_field_names[] = {
> + "common_type",
> + "common_flags",
> + "common_preempt_count",
> + "common_pid",
> + "common_tgid",
> + "common_lock_depth",
Same here.
> +/* Register a trace_uprobe and probe_event */
> +static int register_trace_uprobe(struct trace_uprobe *tp)
> +{
> + struct trace_uprobe *old_tp;
> + int ret;
> +
> + mutex_lock(&uprobe_lock);
> +
> + /* register as an event */
> + old_tp = find_probe_event(tp->call.name, tp->call.system);
> + if (old_tp) {
> + /* delete old event */
> + unregister_trace_uprobe(old_tp);
> + free_trace_uprobe(old_tp);
> + }
> + ret = register_uprobe_event(tp);
> + if (ret) {
> + pr_warning("Faild to register probe event(%d)\n", ret);
"Failed"
> +static int create_trace_uprobe(int argc, char **argv)
> +{
> + /*
> + * Argument syntax:
> + * - Add uprobe: p[:[GRP/]EVENT] VADDR@PID [%REG]
> + *
> + * - Remove uprobe: -:[GRP/]EVENT
> + */
> + struct trace_uprobe *tp;
> + int i, ret = 0;
> + int is_delete = 0;
> + char *arg = NULL, *event = NULL, *group = NULL;
> + void *addr = NULL;
> + pid_t pid = 0;
> + char buf[MAX_EVENT_NAME_LEN];
> +
> + /* argc must be >= 1 */
> + if (argv[0][0] == '-')
> + is_delete = 1;
> + else if (argv[0][0] != 'p') {
> + pr_info("Probe definition must be started with 'p', 'r' or"
> + " '-'.\n");
> + return -EINVAL;
> + }
> +
> + if (argv[0][1] == ':') {
> + event = &argv[0][2];
> + if (strchr(event, '/')) {
> + group = event;
> + event = strchr(group, '/') + 1;
> + event[-1] = '\0';
> + if (strlen(group) == 0) {
> + pr_info("Group name is not specified\n");
> + return -EINVAL;
> + }
> + }
> + if (strlen(event) == 0) {
> + pr_info("Event name is not specified\n");
> + return -EINVAL;
> + }
> + }
> + if (!group)
> + group = UPROBE_EVENT_SYSTEM;
> +
> + if (is_delete) {
> + if (!event) {
> + pr_info("Delete command needs an event name.\n");
> + return -EINVAL;
> + }
> + tp = find_probe_event(event, group);
> + if (!tp) {
> + pr_info("Event %s/%s doesn't exist.\n", group, event);
> + return -ENOENT;
> + }
> + /* delete an event */
> + unregister_trace_uprobe(tp);
Doesn't seem to be under uprobe_lock.
> +/* Make a debugfs interface for controling probe points */
> +static __init int init_uprobe_trace(void)
> +{
> + struct dentry *d_tracer;
> + struct dentry *entry;
> +
> + d_tracer = tracing_init_dentry();
> + if (!d_tracer)
> + return 0;
> +
> + entry = debugfs_create_file("uprobe_events", 0644, d_tracer,
> + NULL, &uprobe_events_ops);
> +
> + /* Event list interface */
> + if (!entry)
> + pr_warning("Could not create debugfs "
> + "'uprobe_events' entry\n");
You can use trace_create_file I think.
> +
> + /* Profile interface */
> + entry = debugfs_create_file("uprobe_profile", 0444, d_tracer,
> + NULL, &uprobe_profile_ops);
> +
> + if (!entry)
> + pr_warning("Could not create debugfs "
> + "'uprobe_profile' entry\n");
> + return 0;
> +}
> +fs_initcall(init_uprobe_trace);
Thanks.
--
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