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authorMichal Marek <mmarek@suse.cz>2010-08-04 14:05:07 +0200
committerMichal Marek <mmarek@suse.cz>2010-08-04 14:05:07 +0200
commit7a996d3ab150bb0e1b71fa182f70199a703efdd1 (patch)
tree96a36947d90c9b96580899abd38cb3b70cd9d40b /Documentation/trace/kprobetrace.txt
parent7cf3d73b4360e91b14326632ab1aeda4cb26308d (diff)
parent9fe6206f400646a2322096b56c59891d530e8d51 (diff)
Merge commit 'v2.6.35' into kbuild/kconfig
Conflicts: scripts/kconfig/Makefile
Diffstat (limited to 'Documentation/trace/kprobetrace.txt')
-rw-r--r--Documentation/trace/kprobetrace.txt61
1 files changed, 35 insertions, 26 deletions
diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 47aabeebbdf6..ec94748ae65b 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -24,6 +24,7 @@ Synopsis of kprobe_events
-------------------------
p[:[GRP/]EVENT] SYMBOL[+offs]|MEMADDR [FETCHARGS] : Set a probe
r[:[GRP/]EVENT] SYMBOL[+0] [FETCHARGS] : Set a return probe
+ -:[GRP/]EVENT : Clear a probe
GRP : Group name. If omitted, use "kprobes" for it.
EVENT : Event name. If omitted, the event name is generated
@@ -37,15 +38,14 @@ Synopsis of kprobe_events
@SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)
$stackN : Fetch Nth entry of stack (N >= 0)
$stack : Fetch stack address.
- $argN : Fetch function argument. (N >= 0)(*)
- $retval : Fetch return value.(**)
- +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(***)
- NAME=FETCHARG: Set NAME as the argument name of FETCHARG.
+ $retval : Fetch return value.(*)
+ +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**)
+ NAME=FETCHARG : Set NAME as the argument name of FETCHARG.
+ FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types
+ (u8/u16/u32/u64/s8/s16/s32/s64) are supported.
- (*) aN may not correct on asmlinkaged functions and at the middle of
- function body.
- (**) only for return probe.
- (***) this is useful for fetching a field of data structures.
+ (*) only for return probe.
+ (**) this is useful for fetching a field of data structures.
Per-Probe Event Filtering
@@ -82,13 +82,16 @@ Usage examples
To add a probe as a new event, write a new definition to kprobe_events
as below.
- echo p:myprobe do_sys_open dfd=$arg0 filename=$arg1 flags=$arg2 mode=$arg3 > /sys/kernel/debug/tracing/kprobe_events
+ echo 'p:myprobe do_sys_open dfd=%ax filename=%dx flags=%cx mode=+4($stack)' > /sys/kernel/debug/tracing/kprobe_events
This sets a kprobe on the top of do_sys_open() function with recording
-1st to 4th arguments as "myprobe" event. As this example shows, users can
-choose more familiar names for each arguments.
+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
+ 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
recording return value as "myretprobe" event.
@@ -97,23 +100,24 @@ recording return value as "myretprobe" event.
cat /sys/kernel/debug/tracing/events/kprobes/myprobe/format
name: myprobe
-ID: 75
+ID: 780
format:
- field:unsigned short common_type; offset:0; size:2;
- field:unsigned char common_flags; offset:2; size:1;
- field:unsigned char common_preempt_count; offset:3; size:1;
- field:int common_pid; offset:4; size:4;
- field:int common_tgid; offset:8; size:4;
+ 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:int common_lock_depth; offset:8; size:4; signed:1;
- field: unsigned long ip; offset:16;tsize:8;
- field: int nargs; offset:24;tsize:4;
- field: unsigned long dfd; offset:32;tsize:8;
- field: unsigned long filename; offset:40;tsize:8;
- field: unsigned long flags; offset:48;tsize:8;
- field: unsigned long mode; offset:56;tsize:8;
+ 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->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.
@@ -121,6 +125,12 @@ print fmt: "(%lx) dfd=%lx filename=%lx flags=%lx mode=%lx", REC->ip, REC->dfd, R
This clears all probe points.
+ Or,
+
+ echo -:myprobe >> kprobe_events
+
+ This clears probe points selectively.
+
Right after definition, each event is disabled by default. For tracing these
events, you need to enable it.
@@ -146,4 +156,3 @@ events, you need to enable it.
returns from SYMBOL(e.g. "sys_open+0x1b/0x1d <- do_sys_open" means kernel
returns from do_sys_open to sys_open+0x1b).
-