From: Masami Hiramatsu <[email protected]>
$params is similar to $vars but matches only function parameters not
local variables.
Thus, this is useful for tracing function parameter changing or tracing
function call with parameters.
Testing it:
# perf probe tcp_sendmsg '$params'
Added new event:
probe:tcp_sendmsg (on tcp_sendmsg with $params)
You can now use it in all perf tools, such as:
perf record -e probe:tcp_sendmsg -aR sleep 1
# perf probe -l
probe:tcp_sendmsg (on tcp_sendmsg@acme/git/linux/net/ipv4/tcp.c with iocb
sk msg size)
# perf record -a -e probe:*
press some random letters to generate TCP (sshd) traffic...
^C[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.223 MB perf.data (6 samples) ]
# perf script
sshd 6385 [2] 3.907529: probe:tcp_sendmsg: iocb=0xffff8800ac4cfe70
sk=0xffff88042196c140 msg=0xffff8800ac4cfda8 size=0x24
sshd 6385 [2] 4.138973: probe:tcp_sendmsg: iocb=0xffff8800ac4cfe70
sk=0xffff88042196c140 msg=0xffff8800ac4cfda8 size=0x24
sshd 6385 [2] 4.378966: probe:tcp_sendmsg: iocb=0xffff8800ac4cfe70
sk=0xffff88042196c140 msg=0xffff8800ac4cfda8 size=0x24
sshd 6385 [2] 4.603681: probe:tcp_sendmsg: iocb=0xffff8800ac4cfe70
sk=0xffff88042196c140 msg=0xffff8800ac4cfda8 size=0x24
sshd 6385 [2] 4.818455: probe:tcp_sendmsg: iocb=0xffff8800ac4cfe70
sk=0xffff88042196c140 msg=0xffff8800ac4cfda8 size=0x24
sshd 6385 [2] 5.043603: probe:tcp_sendmsg: iocb=0xffff8800ac4cfe70
sk=0xffff88042196c140 msg=0xffff8800ac4cfda8 size=0x24
# cat /sys/kernel/debug/tracing/events/probe/tcp_sendmsg/format
name: tcp_sendmsg
ID: 1927
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:8; size:8; signed:0;
field:u64 iocb; offset:16; size:8; signed:0;
field:u64 sk; offset:24; size:8; signed:0;
field:u64 msg; offset:32; size:8; signed:0;
field:u64 size; offset:40; size:8; signed:0;
print fmt: "(%lx) iocb=0x%Lx sk=0x%Lx msg=0x%Lx size=0x%Lx", REC->__probe_ip,
REC->iocb, REC->sk, REC->msg, REC->size
#
Do some system wide tracing of this probe + write syscalls:
# perf trace -e write --ev probe:* --filter-pids 6385
462.612 (0.010 ms): bash/19153 write(fd: 1</dev/pts/1>, buf: 0x7f7556c78000,
count: 29 ) = 29
462.701 (0.027 ms): sshd/19152 write(fd: 3<socket:[63117]>, buf:
0x7f78dd12e160, count: 68 ) ...
462.701 ( ): probe:tcp_sendmsg:(ffffffff8163db30)
iocb=0xffff8803ebec7e70 sk=0xffff88042196ab80 msg=0xffff8803ebec7da8 size=0x44)
462.710 (0.035 ms): sshd/19152 ... [continued]: write()) = 68
462.787 (0.009 ms): bash/19153 write(fd: 2</dev/pts/1>, buf: 0x7f7556c77000,
count: 22 ) = 22
462.865 (0.002 ms): sshd/19152 write(fd: 3<socket:[63117]>, buf:
0x7f78dd12e160, count: 68 ) ...
462.865 ( ): probe:tcp_sendmsg:(ffffffff8163db30)
iocb=0xffff8803ebec7e70 sk=0xffff88042196ab80 msg=0xffff8803ebec7da8 size=0x44)
462.873 (0.010 ms): sshd/19152 ... [continued]: write()) = 68
Signed-off-by: Masami Hiramatsu <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Hemant Kumar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link:
http://lkml.kernel.org/r/[email protected]
[ Add some examples to the changelog message showing how to use it ]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
tools/perf/Documentation/perf-probe.txt | 2 +-
tools/perf/util/probe-finder.c | 29 ++++++++++++++++-------------
tools/perf/util/probe-finder.h | 3 +++
3 files changed, 20 insertions(+), 14 deletions(-)
diff --git a/tools/perf/Documentation/perf-probe.txt
b/tools/perf/Documentation/perf-probe.txt
index a272f2e..ad3e355 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -151,7 +151,7 @@ Each probe argument follows below syntax.
[NAME=]LOCALVAR|$retval|%REG|@SYMBOL[:TYPE]
'NAME' specifies the name of this argument (optional). You can use the name of
local variable, local data structure member (e.g. var->field, var.field2),
local array with fixed index (e.g. array[1], var->array[0], var->pointer[2]),
or kprobe-tracer argument format (e.g. $retval, %ax, etc). Note that the name
of this argument will be set as the last member name if you specify a local
data structure member (e.g. field2 for 'var->field1.field2'.)
-'$vars' special argument is also available for NAME, it is expanded to the
local variables which can access at given probe point.
+'$vars' and '$params' special arguments are also available for NAME, '$vars'
is expanded to the local variables (including function parameters) which can
access at given probe point. '$params' is expanded to only the function
parameters.
'TYPE' casts the type of this argument (optional). If omitted, perf probe
automatically set the type based on debuginfo. You can specify 'string' type
only for the local variable or structure member which is an array of or a
pointer to 'char' or 'unsigned char' type.
On x86 systems %REG is always the short form of the register: for example %AX.
%RAX or %EAX is not valid.
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index b5bf9d5..63d3389 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1087,6 +1087,7 @@ found:
struct local_vars_finder {
struct probe_finder *pf;
struct perf_probe_arg *args;
+ bool vars;
int max_args;
int nargs;
int ret;
@@ -1101,7 +1102,7 @@ static int copy_variables_cb(Dwarf_Die *die_mem, void
*data)
tag = dwarf_tag(die_mem);
if (tag == DW_TAG_formal_parameter ||
- tag == DW_TAG_variable) {
+ (tag == DW_TAG_variable && vf->vars)) {
if (convert_variable_location(die_mem, vf->pf->addr,
vf->pf->fb_ops, &pf->sp_die,
NULL) == 0) {
@@ -1127,26 +1128,28 @@ static int expand_probe_args(Dwarf_Die *sc_die, struct
probe_finder *pf,
Dwarf_Die die_mem;
int i;
int n = 0;
- struct local_vars_finder vf = {.pf = pf, .args = args,
+ struct local_vars_finder vf = {.pf = pf, .args = args, .vars = false,
.max_args = MAX_PROBE_ARGS, .ret = 0};
for (i = 0; i < pf->pev->nargs; i++) {
/* var never be NULL */
- if (strcmp(pf->pev->args[i].var, "$vars") == 0) {
- pr_debug("Expanding $vars into:");
- vf.nargs = n;
- /* Special local variables */
- die_find_child(sc_die, copy_variables_cb, (void *)&vf,
- &die_mem);
- pr_debug(" (%d)\n", vf.nargs - n);
- if (vf.ret < 0)
- return vf.ret;
- n = vf.nargs;
- } else {
+ if (strcmp(pf->pev->args[i].var, PROBE_ARG_VARS) == 0)
+ vf.vars = true;
+ else if (strcmp(pf->pev->args[i].var, PROBE_ARG_PARAMS) != 0) {
/* Copy normal argument */
args[n] = pf->pev->args[i];
n++;
+ continue;
}
+ pr_debug("Expanding %s into:", pf->pev->args[i].var);
+ vf.nargs = n;
+ /* Special local variables */
+ die_find_child(sc_die, copy_variables_cb, (void *)&vf,
+ &die_mem);
+ pr_debug(" (%d)\n", vf.nargs - n);
+ if (vf.ret < 0)
+ return vf.ret;
+ n = vf.nargs;
}
return n;
}
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index ebf8c8c..f53553d 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -10,6 +10,9 @@
#define MAX_PROBES 128
#define MAX_PROBE_ARGS 128
+#define PROBE_ARG_VARS "$vars"
+#define PROBE_ARG_PARAMS "$params"
+
static inline int is_c_varname(const char *name)
{
/* TODO */
--
2.1.0
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