From: Masami Hiramatsu <mhiramat@kernel•org>
To: Masami Hiramatsu <mhiramat@kernel•org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux•vnet.ibm.com>,
Arnaldo Carvalho de Melo <acme@kernel•org>,
Steven Rostedt <rostedt@goodmis•org>,
Ingo Molnar <mingo@redhat•com>,
linux-kernel@vger•kernel.org, linuxppc-dev@lists•ozlabs.org,
Ananth N Mavinakayanahalli <ananth@linux•vnet.ibm.com>,
Michael Ellerman <mpe@ellerman•id.au>
Subject: Re: [PATCH v4 2/3] perf: kretprobes: offset from reloc_sym if kernel supports it
Date: Sat, 4 Mar 2017 13:34:05 +0900 [thread overview]
Message-ID: <20170304133405.176da43d40cec7cb00e757e1@kernel.org> (raw)
In-Reply-To: <20170304113551.6a008b969a3ed713729cbd57@kernel.org>
[-- Attachment #1: Type: text/plain, Size: 2838 bytes --]
On Sat, 4 Mar 2017 11:35:51 +0900
Masami Hiramatsu <mhiramat@kernel•org> wrote:
> On Sat, 4 Mar 2017 09:49:11 +0900
> Masami Hiramatsu <mhiramat@kernel•org> wrote:
>
> > On Thu, 2 Mar 2017 23:25:06 +0530
> > "Naveen N. Rao" <naveen.n.rao@linux•vnet.ibm.com> wrote:
> >
> > > We indicate support for accepting sym+offset with kretprobes through a
> > > line in ftrace README. Parse the same to identify support and choose the
> > > appropriate format for kprobe_events.
> >
> > Could you give us an example of this change here? :)
> > for example, comment of commit 613f050d68a8 .
> >
> > I think the code is OK, but we need actual example of result.
>
> Hi Naveen,
>
> I've tried following commands
>
> $ grep "[Tt] user_read$" /proc/kallsyms
> 0000000000000000 T user_read
> 0000000000000000 t user_read
> $ sudo ./perf probe -D user_read%return
> r:probe/user_read _text+3539616
> r:probe/user_read_1 _text+3653408
>
> OK, looks good. However, when I set the retprobes, I got an error.
>
> $ sudo ./perf probe -a user_read%return
> Failed to write event: Invalid argument
> Error: Failed to add events.
>
> And kernel rejected that.
>
> $ dmesg -k | tail -n 1
> [ 850.315068] Given offset is not valid for return probe.
>
> Hmm, curious..
Ah, I see.
static int create_trace_kprobe(int argc, char **argv)
...
} else {
/* a symbol specified */
symbol = argv[1];
/* TODO: support .init module functions */
ret = traceprobe_split_symbol_offset(symbol, &offset);
if (ret) {
pr_info("Failed to parse symbol.\n");
return ret;
}
if (offset && is_return &&
!arch_function_offset_within_entry(offset)) {
pr_info("Given offset is not valid for return probe.\n");
return -EINVAL;
}
}
So, actually, traceprobe_split_symbol_offset() just split out symbol
and offset from symbol string (e.g. "_text+3539616").
So, you should use kallsyms_lookup_size_offset() here again to check
offset.
Please try attached patch (I've already tested on x86-64).
$ sudo ./perf probe -a user_read%return
Added new events:
probe:user_read (on user_read%return)
probe:user_read_1 (on user_read%return)
You can now use it in all perf tools, such as:
perf record -e probe:user_read_1 -aR sleep 1
$ sudo ./perf probe -l
probe:user_read (on user_read%return@security/keys/user_defined.c)
probe:user_read_1 (on user_read%return@selinux/ss/policydb.c)
$ sudo cat /sys/kernel/debug/kprobes/list
ffffffff9637bf70 r user_read+0x0 [DISABLED][FTRACE]
ffffffff963602f0 r user_read+0x0 [DISABLED][FTRACE]
Thank you,
--
Masami Hiramatsu <mhiramat@kernel•org>
[-- Attachment #2: tracing-kprobe-check-kretprobe --]
[-- Type: application/octet-stream, Size: 2894 bytes --]
tracing: kprobe: Check kretprobe offset from symbol correctly
From: Masami Hiramatsu <mhiramat@kernel•org>
Check the kretprobe event offset from the nearest symbol correctly
instead of checking given offset value.
This will allow users to specify the relative offset from _text
or _stext so that they can put a kretprobe on one of same-name
functions.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel•org>
---
include/linux/kprobes.h | 9 +++++++++
kernel/kprobes.c | 9 ---------
kernel/trace/trace_kprobe.c | 18 +++++++++++++++++-
3 files changed, 26 insertions(+), 10 deletions(-)
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 862f87a..6a92734 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -44,6 +44,15 @@
#ifdef CONFIG_KPROBES
#include <asm/kprobes.h>
+/*
+ * Some oddball architectures like 64bit powerpc have function descriptors
+ * so this must be overridable.
+ */
+#ifndef kprobe_lookup_name
+#define kprobe_lookup_name(name, addr) \
+ addr = ((kprobe_opcode_t *)(kallsyms_lookup_name(name)))
+#endif
+
/* kprobe_status settings */
#define KPROBE_HIT_ACTIVE 0x00000001
#define KPROBE_HIT_SS 0x00000002
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index a77f9d7..9236f3f 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -58,15 +58,6 @@
#define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)
-/*
- * Some oddball architectures like 64bit powerpc have function descriptors
- * so this must be overridable.
- */
-#ifndef kprobe_lookup_name
-#define kprobe_lookup_name(name, addr) \
- addr = ((kprobe_opcode_t *)(kallsyms_lookup_name(name)))
-#endif
-
static int kprobes_initialized;
static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index c60f9dc..59f2b2f 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -587,6 +587,22 @@ static int trace_kprobe_module_callback(struct notifier_block *nb,
return NOTIFY_DONE;
}
+static bool function_offset_within_entry(const char *sym, unsigned long offs)
+{
+ void *addr = NULL;
+
+ kprobe_lookup_name(sym, addr);
+ if (!addr)
+ return false;
+ addr += offs;
+
+ if (kallsyms_lookup_size_offset((unsigned long)addr, NULL, &offs) &&
+ offs == 0)
+ return true;
+
+ return false;
+}
+
static struct notifier_block trace_kprobe_module_nb = {
.notifier_call = trace_kprobe_module_callback,
.priority = 1 /* Invoked after kprobe module callback */
@@ -695,7 +711,7 @@ static int create_trace_kprobe(int argc, char **argv)
return ret;
}
if (offset && is_return &&
- !arch_function_offset_within_entry(offset)) {
+ !function_offset_within_entry(symbol, offset)) {
pr_info("Given offset is not valid for return probe.\n");
return -EINVAL;
}
next prev parent reply other threads:[~2017-03-04 4:34 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-22 13:53 [PATCH v2 0/5] kretprobe fixes Naveen N. Rao
2017-02-22 13:53 ` [PATCH v2 1/5] kretprobes: ensure probe location is at function entry Naveen N. Rao
2017-02-22 13:53 ` [PATCH v2 2/5] powerpc: kretprobes: override default function entry offset Naveen N. Rao
2017-02-24 19:57 ` Arnaldo Carvalho de Melo
2017-02-27 12:56 ` Michael Ellerman
2017-02-25 2:45 ` Ananth N Mavinakayanahalli
2017-02-22 13:53 ` [PATCH v2 3/5] trace/kprobes: allow return probes with offsets and absolute addresses Naveen N. Rao
2017-02-27 16:32 ` Steven Rostedt
2017-02-27 16:52 ` [PATCH v2 3.5/5] trace/kprobes: Add back warning about offset in return probes Steven Rostedt (VMware)
2017-02-28 0:01 ` Masami Hiramatsu
2017-03-01 15:16 ` Naveen N. Rao
2017-02-22 13:53 ` [PATCH v2 4/5] perf: kretprobes: offset from reloc_sym if kernel supports it Naveen N. Rao
2017-02-23 9:10 ` Masami Hiramatsu
2017-02-23 11:37 ` [PATCH v3 1/2] perf: probe: generalize probe event file open routine Naveen N. Rao
2017-02-24 16:46 ` Masami Hiramatsu
2017-02-24 20:07 ` Arnaldo Carvalho de Melo
2017-03-01 15:12 ` Naveen N. Rao
2017-02-23 11:37 ` [PATCH v3 2/2] perf: kretprobes: offset from reloc_sym if kernel supports it Naveen N. Rao
2017-02-24 17:12 ` Masami Hiramatsu
2017-03-01 15:11 ` Naveen N. Rao
2017-02-23 19:16 ` [PATCH v2 4/5] " Naveen N. Rao
2017-02-24 17:29 ` Masami Hiramatsu
2017-02-24 20:11 ` Arnaldo Carvalho de Melo
2017-02-24 23:55 ` Masami Hiramatsu
2017-03-01 15:14 ` Naveen N. Rao
2017-03-02 17:55 ` Naveen N. Rao
2017-03-02 17:55 ` [PATCH v4 1/3] perf: probe: factor out the ftrace README scanning Naveen N. Rao
2017-03-04 0:09 ` Masami Hiramatsu
2017-03-07 20:45 ` Steven Rostedt
2017-03-02 17:55 ` [PATCH v4 2/3] perf: kretprobes: offset from reloc_sym if kernel supports it Naveen N. Rao
2017-03-04 0:49 ` Masami Hiramatsu
2017-03-04 2:35 ` Masami Hiramatsu
2017-03-04 2:38 ` Masami Hiramatsu
2017-03-04 4:34 ` Masami Hiramatsu [this message]
2017-03-06 16:20 ` Naveen N. Rao
2017-03-06 17:49 ` Naveen N. Rao
2017-03-06 21:06 ` Masami Hiramatsu
2017-03-07 10:47 ` [PATCH v4 2/3] perf: kretprobes: offset from reloc_sym if kernel Naveen N. Rao
2017-03-07 10:47 ` [RESEND PATCH 1/6] trace/kprobes: fix check for kretprobe offset within function entry Naveen N. Rao
2017-03-07 20:47 ` Steven Rostedt
2017-03-08 8:01 ` Naveen N. Rao
2017-03-07 10:47 ` [RESEND PATCH 2/6] powerpc: kretprobes: override default function entry offset Naveen N. Rao
2017-03-07 10:47 ` [RESEND PATCH 3/6] perf: probe: factor out the ftrace README scanning Naveen N. Rao
2017-03-07 10:47 ` [RESEND PATCH 4/6] perf: kretprobes: offset from reloc_sym if kernel supports it Naveen N. Rao
2017-03-07 10:47 ` [PATCH 5/6] perf: probes: move ftrace README parsing logic into trace-event-parse.c Naveen N. Rao
2017-03-07 14:03 ` Masami Hiramatsu
2017-03-07 14:29 ` Naveen N. Rao
2017-03-07 15:51 ` Masami Hiramatsu
2017-03-07 16:31 ` Naveen N. Rao
2017-03-07 10:47 ` [RESEND PATCH 6/6] perf: powerpc: choose local entry point with kretprobes Naveen N. Rao
2017-03-07 16:49 ` [PATCH v2 " Naveen N. Rao
2017-03-06 15:04 ` [PATCH v4 2/3] perf: kretprobes: offset from reloc_sym if kernel supports it Naveen N. Rao
2017-03-06 21:14 ` Masami Hiramatsu
2017-03-02 17:55 ` [PATCH v4 3/3] perf: powerpc: choose local entry point with kretprobes Naveen N. Rao
2017-03-04 0:50 ` Masami Hiramatsu
2017-03-02 19:06 ` [PATCH v2 4/5] perf: kretprobes: offset from reloc_sym if kernel supports it Arnaldo Carvalho de Melo
2017-02-22 13:53 ` [PATCH v2 5/5] perf: powerpc: choose local entry point with kretprobes Naveen N. Rao
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