diff options
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/trace/kprobetrace.rst (renamed from Documentation/trace/kprobetrace.txt) | 100 |
2 files changed, 55 insertions, 46 deletions
diff --git a/Documentation/trace/index.rst b/Documentation/trace/index.rst index 947c6db021a9..c8e2130a7318 100644 --- a/Documentation/trace/index.rst +++ b/Documentation/trace/index.rst @@ -9,3 +9,4 @@ Linux Tracing Technologies tracepoint-analysis ftrace ftrace-uses + kprobetrace diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.rst index 1a3a3d6bc2a8..3e0f971b12de 100644 --- a/Documentation/trace/kprobetrace.txt +++ b/Documentation/trace/kprobetrace.rst @@ -1,8 +1,8 @@ - Kprobe-based Event Tracing - ========================== - - Documentation is written by Masami Hiramatsu +========================== +Kprobe-based Event Tracing +========================== +:Author: Masami Hiramatsu Overview -------- @@ -23,6 +23,8 @@ current_tracer. Instead of that, add probe points via Synopsis of kprobe_events ------------------------- +:: + p[:[GRP/]EVENT] [MOD:]SYM[+offs]|MEMADDR [FETCHARGS] : Set a probe r[MAXACTIVE][:[GRP/]EVENT] [MOD:]SYM[+0] [FETCHARGS] : Set a return probe -:[GRP/]EVENT : Clear a probe @@ -66,7 +68,7 @@ String type is a special type, which fetches a "null-terminated" string from kernel space. This means it will fail and store NULL if the string container has been paged out. Bitfield is another special type, which takes 3 parameters, bit-width, bit- -offset, and container-size (usually 32). The syntax is; +offset, and container-size (usually 32). The syntax is:: b<bit-width>@<bit-offset>/<container-size> @@ -75,7 +77,7 @@ For $comm, the default type is "string"; any other type is invalid. Per-Probe Event Filtering ------------------------- - Per-probe event filtering feature allows you to set different filter on each +Per-probe event filtering feature allows you to set different filter on each probe and gives you what arguments will be shown in trace buffer. If an event name is specified right after 'p:' or 'r:' in kprobe_events, it adds an event under tracing/events/kprobes/<EVENT>, at the directory you can see 'id', @@ -96,87 +98,93 @@ id: Event Profiling --------------- - You can check the total number of probe hits and probe miss-hits via +You can check the total number of probe hits and probe miss-hits via /sys/kernel/debug/tracing/kprobe_profile. - The first column is event name, the second is the number of probe hits, +The first column is event name, the second is the number of probe hits, the third is the number of probe miss-hits. Usage examples -------------- To add a probe as a new event, write a new definition to kprobe_events -as below. +as below:: echo 'p:myprobe do_sys_open dfd=%ax filename=%dx flags=%cx mode=+4($stack)' > /sys/kernel/debug/tracing/kprobe_events - This sets a kprobe on the top of do_sys_open() function with recording +This sets a kprobe on the top of do_sys_open() function with recording 1st to 4th arguments as "myprobe" event. Note, which register/stack entry is assigned to each function argument depends on arch-specific ABI. If you unsure the ABI, please try to use probe subcommand of perf-tools (you can find it under tools/perf/). As this example shows, users can choose more familiar names for each arguments. +:: echo 'r:myretprobe do_sys_open $retval' >> /sys/kernel/debug/tracing/kprobe_events - This sets a kretprobe on the return point of do_sys_open() function with +This sets a kretprobe on the return point of do_sys_open() function with recording return value as "myretprobe" event. - You can see the format of these events via +You can see the format of these events via /sys/kernel/debug/tracing/events/kprobes/<EVENT>/format. +:: cat /sys/kernel/debug/tracing/events/kprobes/myprobe/format -name: myprobe -ID: 780 -format: - field:unsigned short common_type; offset:0; size:2; signed:0; - field:unsigned char common_flags; offset:2; size:1; signed:0; - field:unsigned char common_preempt_count; offset:3; size:1;signed:0; - field:int common_pid; offset:4; size:4; signed:1; + name: myprobe + ID: 780 + format: + field:unsigned short common_type; offset:0; size:2; signed:0; + field:unsigned char common_flags; offset:2; size:1; signed:0; + field:unsigned char common_preempt_count; offset:3; size:1;signed:0; + field:int common_pid; offset:4; size:4; signed:1; - field:unsigned long __probe_ip; offset:12; size:4; signed:0; - field:int __probe_nargs; offset:16; size:4; signed:1; - field:unsigned long dfd; offset:20; size:4; signed:0; - field:unsigned long filename; offset:24; size:4; signed:0; - field:unsigned long flags; offset:28; size:4; signed:0; - field:unsigned long mode; offset:32; size:4; signed:0; + field:unsigned long __probe_ip; offset:12; size:4; signed:0; + field:int __probe_nargs; offset:16; size:4; signed:1; + field:unsigned long dfd; offset:20; size:4; signed:0; + field:unsigned long filename; offset:24; size:4; signed:0; + field:unsigned long flags; offset:28; size:4; signed:0; + field:unsigned long mode; offset:32; size:4; signed:0; -print fmt: "(%lx) dfd=%lx filename=%lx flags=%lx mode=%lx", REC->__probe_ip, -REC->dfd, REC->filename, REC->flags, REC->mode + print fmt: "(%lx) dfd=%lx filename=%lx flags=%lx mode=%lx", REC->__probe_ip, + REC->dfd, REC->filename, REC->flags, REC->mode - You can see that the event has 4 arguments as in the expressions you specified. +You can see that the event has 4 arguments as in the expressions you specified. +:: echo > /sys/kernel/debug/tracing/kprobe_events - This clears all probe points. +This clears all probe points. - Or, +Or, +:: echo -:myprobe >> kprobe_events - This clears probe points selectively. +This clears probe points selectively. - Right after definition, each event is disabled by default. For tracing these +Right after definition, each event is disabled by default. For tracing these events, you need to enable it. +:: echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable echo 1 > /sys/kernel/debug/tracing/events/kprobes/myretprobe/enable - And you can see the traced information via /sys/kernel/debug/tracing/trace. +And you can see the traced information via /sys/kernel/debug/tracing/trace. +:: cat /sys/kernel/debug/tracing/trace -# tracer: nop -# -# TASK-PID CPU# TIMESTAMP FUNCTION -# | | | | | - <...>-1447 [001] 1038282.286875: myprobe: (do_sys_open+0x0/0xd6) dfd=3 filename=7fffd1ec4440 flags=8000 mode=0 - <...>-1447 [001] 1038282.286878: myretprobe: (sys_openat+0xc/0xe <- do_sys_open) $retval=fffffffffffffffe - <...>-1447 [001] 1038282.286885: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=40413c flags=8000 mode=1b6 - <...>-1447 [001] 1038282.286915: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=3 - <...>-1447 [001] 1038282.286969: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=4041c6 flags=98800 mode=10 - <...>-1447 [001] 1038282.286976: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=3 - - - Each line shows when the kernel hits an event, and <- SYMBOL means kernel + # tracer: nop + # + # TASK-PID CPU# TIMESTAMP FUNCTION + # | | | | | + <...>-1447 [001] 1038282.286875: myprobe: (do_sys_open+0x0/0xd6) dfd=3 filename=7fffd1ec4440 flags=8000 mode=0 + <...>-1447 [001] 1038282.286878: myretprobe: (sys_openat+0xc/0xe <- do_sys_open) $retval=fffffffffffffffe + <...>-1447 [001] 1038282.286885: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=40413c flags=8000 mode=1b6 + <...>-1447 [001] 1038282.286915: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=3 + <...>-1447 [001] 1038282.286969: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=4041c6 flags=98800 mode=10 + <...>-1447 [001] 1038282.286976: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=3 + + +Each line shows when the kernel hits an event, and <- SYMBOL means kernel returns from SYMBOL(e.g. "sys_open+0x1b/0x1d <- do_sys_open" means kernel returns from do_sys_open to sys_open+0x1b). |