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tracing: Provide trace events interface for uprobes

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Implements trace_event support for uprobes. In its current form
it can be used to put probes at a specified offset in a file and
dump the required registers when the code flow reaches the
probed address.

The following example shows how to dump the instruction pointer
and %ax a register at the probed text address.  Here we are
trying to probe zfree in /bin/zsh:

 # cd /sys/kernel/debug/tracing/
 # cat /proc/`pgrep  zsh`/maps | grep /bin/zsh | grep r-xp
 00400000-0048a000 r-xp 00000000 08:03 130904 /bin/zsh
 # objdump -T /bin/zsh | grep -w zfree
 0000000000446420 g    DF .text  0000000000000012  Base
 zfree # echo 'p /bin/zsh:0x46420 %ip %ax' > uprobe_events
 # cat uprobe_events
 p:uprobes/p_zsh_0x46420 /bin/zsh:0x0000000000046420
 # echo 1 > events/uprobes/enable
 # sleep 20
 # echo 0 > events/uprobes/enable
 # cat trace
 # tracer: nop
 #
 #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
 #              | |       |          |         |
              zsh-24842 [006] 258544.995456: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
              zsh-24842 [007] 258545.000270: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
              zsh-24842 [002] 258545.043929: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
              zsh-24842 [004] 258547.046129: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com>
Cc: Linux-mm <linux-mm@kvack.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120411103043.GB29437@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Srikar Dronamraju
2012-04-11 16:00:43 +05:30
committed by Ingo Molnar
parent 8ab83f5647
commit f3f096cfed
9 changed files with 919 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/trace/trace_probe.c
+10 -4
View File
@@ -550,7 +550,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
/* Recursive argument parser */
static int parse_probe_arg(char *arg, const struct fetch_type *t,
struct fetch_param *f, bool is_return)
struct fetch_param *f, bool is_return, bool is_kprobe)
{
unsigned long param;
long offset;
@@ -558,6 +558,11 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
int ret;
ret = 0;
/* Until uprobe_events supports only reg arguments */
if (!is_kprobe && arg[0] != '%')
return -EINVAL;
switch (arg[0]) {
case '$':
ret = parse_probe_vars(arg + 1, t, f, is_return);
@@ -619,7 +624,8 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
return -ENOMEM;
dprm->offset = offset;
ret = parse_probe_arg(arg, t2, &dprm->orig, is_return);
ret = parse_probe_arg(arg, t2, &dprm->orig, is_return,
is_kprobe);
if (ret)
kfree(dprm);
else {
@@ -677,7 +683,7 @@ static int __parse_bitfield_probe_arg(const char *bf,
/* String length checking wrapper */
int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
struct probe_arg *parg, bool is_return)
struct probe_arg *parg, bool is_return, bool is_kprobe)
{
const char *t;
int ret;
@@ -703,7 +709,7 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
}
parg->offset = *size;
*size += parg->type->size;
ret = parse_probe_arg(arg, parg->type, &parg->fetch, is_return);
ret = parse_probe_arg(arg, parg->type, &parg->fetch, is_return, is_kprobe);
if (ret >= 0 && t != NULL)
ret = __parse_bitfield_probe_arg(t, parg->type, &parg->fetch);