* [PATCH v5 1/2] tracing/kprobes: Return EADDRNOTAVAIL when func matches several symbols
[not found] <20231018144030.86885-1-flaniel@linux.microsoft.com>
@ 2023-10-18 14:40 ` Francis Laniel
2023-10-18 14:40 ` [PATCH v5 2/2] selftests/ftrace: Add new test case which checks non unique symbol Francis Laniel
1 sibling, 0 replies; 3+ messages in thread
From: Francis Laniel @ 2023-10-18 14:40 UTC (permalink / raw)
To: linux-trace-kernel
Cc: Masami Hiramatsu, stable, Francis Laniel, Steven Rostedt,
linux-kernel
Previously to this commit, if func matches several symbols, a kprobe, being
either sysfs or PMU, would only be installed for the first matching address.
This could lead to some misunderstanding when some BPF code was never called
because it was attached to a function which was indeed not called, because
the effectively called one has no kprobes attached.
So, this commit returns EADDRNOTAVAIL when func matches several symbols.
This way, user needs to use address to remove the ambiguity.
Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com>
Link: https://lore.kernel.org/lkml/20230819101105.b0c104ae4494a7d1f2eea742@kernel.org/
---
kernel/trace/trace_kprobe.c | 63 +++++++++++++++++++++++++++++++++++++
kernel/trace/trace_probe.h | 1 +
2 files changed, 64 insertions(+)
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 3d7a180a8427..a8fef6ab0872 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -705,6 +705,25 @@ static struct notifier_block trace_kprobe_module_nb = {
.priority = 1 /* Invoked after kprobe module callback */
};
+static int count_symbols(void *data, unsigned long unused)
+{
+ unsigned int *count = data;
+
+ (*count)++;
+
+ return 0;
+}
+
+static unsigned int number_of_same_symbols(char *func_name)
+{
+ unsigned int count;
+
+ count = 0;
+ kallsyms_on_each_match_symbol(count_symbols, func_name, &count);
+
+ return count;
+}
+
static int __trace_kprobe_create(int argc, const char *argv[])
{
/*
@@ -836,6 +855,31 @@ static int __trace_kprobe_create(int argc, const char *argv[])
}
}
+ if (symbol && !strchr(symbol, ':')) {
+ unsigned int count;
+
+ count = number_of_same_symbols(symbol);
+ if (count > 1) {
+ /*
+ * Users should use ADDR to remove the ambiguity of
+ * using KSYM only.
+ */
+ trace_probe_log_err(0, NON_UNIQ_SYMBOL);
+ ret = -EADDRNOTAVAIL;
+
+ goto error;
+ } else if (count == 0) {
+ /*
+ * We can return ENOENT earlier than when register the
+ * kprobe.
+ */
+ trace_probe_log_err(0, BAD_PROBE_ADDR);
+ ret = -ENOENT;
+
+ goto error;
+ }
+ }
+
trace_probe_log_set_index(0);
if (event) {
ret = traceprobe_parse_event_name(&event, &group, gbuf,
@@ -1695,6 +1739,7 @@ static int unregister_kprobe_event(struct trace_kprobe *tk)
}
#ifdef CONFIG_PERF_EVENTS
+
/* create a trace_kprobe, but don't add it to global lists */
struct trace_event_call *
create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
@@ -1705,6 +1750,24 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
int ret;
char *event;
+ if (func) {
+ unsigned int count;
+
+ count = number_of_same_symbols(func);
+ if (count > 1)
+ /*
+ * Users should use addr to remove the ambiguity of
+ * using func only.
+ */
+ return ERR_PTR(-EADDRNOTAVAIL);
+ else if (count == 0)
+ /*
+ * We can return ENOENT earlier than when register the
+ * kprobe.
+ */
+ return ERR_PTR(-ENOENT);
+ }
+
/*
* local trace_kprobes are not added to dyn_event, so they are never
* searched in find_trace_kprobe(). Therefore, there is no concern of
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 02b432ae7513..850d9ecb6765 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -450,6 +450,7 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
C(BAD_MAXACT, "Invalid maxactive number"), \
C(MAXACT_TOO_BIG, "Maxactive is too big"), \
C(BAD_PROBE_ADDR, "Invalid probed address or symbol"), \
+ C(NON_UNIQ_SYMBOL, "The symbol is not unique"), \
C(BAD_RETPROBE, "Retprobe address must be an function entry"), \
C(NO_TRACEPOINT, "Tracepoint is not found"), \
C(BAD_ADDR_SUFFIX, "Invalid probed address suffix"), \
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH v5 2/2] selftests/ftrace: Add new test case which checks non unique symbol
[not found] <20231018144030.86885-1-flaniel@linux.microsoft.com>
2023-10-18 14:40 ` [PATCH v5 1/2] tracing/kprobes: Return EADDRNOTAVAIL when func matches several symbols Francis Laniel
@ 2023-10-18 14:40 ` Francis Laniel
2023-10-18 16:55 ` Greg KH
1 sibling, 1 reply; 3+ messages in thread
From: Francis Laniel @ 2023-10-18 14:40 UTC (permalink / raw)
To: linux-trace-kernel
Cc: Masami Hiramatsu, stable, Francis Laniel, Steven Rostedt,
Shuah Khan, linux-kernel, linux-kselftest
If name_show() is non unique, this test will try to install a kprobe on this
function which should fail returning EADDRNOTAVAIL.
On kernel where name_show() is not unique, this test is skipped.
Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com>
---
.../ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc | 13 +++++++++++++
1 file changed, 13 insertions(+)
create mode 100644 tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc
diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc
new file mode 100644
index 000000000000..bc9514428dba
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_non_uniq_symbol.tc
@@ -0,0 +1,13 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Test failure of registering kprobe on non unique symbol
+# requires: kprobe_events
+
+SYMBOL='name_show'
+
+# We skip this test on kernel where SYMBOL is unique or does not exist.
+if [ "$(grep -c -E "[[:alnum:]]+ t ${SYMBOL}" /proc/kallsyms)" -le '1' ]; then
+ exit_unsupported
+fi
+
+! echo "p:test_non_unique ${SYMBOL}" > kprobe_events
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread