[PATCH v4 0/3] selftests: livepatch: test livepatching a kprobed function

[PATCH v4 0/3] selftests: livepatch: test livepatching a kprobed function

[Michael Vetter]

Thanks to Miroslav, Petr and Marcos for the reviews!

V4:
Use variable for /sys/kernel/debug.
Be consistent with "" around variables.
Fix path in commit message to /sys/kernel/debug/kprobes/enabled.

V3:
Save and restore kprobe state also when test fails, by integrating it
into setup_config() and cleanup().
Rename SYSFS variables in a more logical way.
Sort test modules in alphabetical order.
Rename module description.

V2:
Save and restore kprobe state.

Michael Vetter (3):
  selftests: livepatch: rename KLP_SYSFS_DIR to SYSFS_KLP_DIR
  selftests: livepatch: save and restore kprobe state
  selftests: livepatch: test livepatching a kprobed function

 tools/testing/selftests/livepatch/Makefile    |  3 +-
 .../testing/selftests/livepatch/functions.sh  | 19 ++++--
 .../selftests/livepatch/test-kprobe.sh        | 62 +++++++++++++++++++
 .../selftests/livepatch/test_modules/Makefile |  3 +-
 .../livepatch/test_modules/test_klp_kprobe.c  | 38 ++++++++++++
 5 files changed, 117 insertions(+), 8 deletions(-)
 create mode 100755 tools/testing/selftests/livepatch/test-kprobe.sh
 create mode 100644 tools/testing/selftests/livepatch/test_modules/test_klp_kprobe.c

-- 
2.46.1

[PATCH v4 1/3] selftests: livepatch: rename KLP_SYSFS_DIR to SYSFS_KLP_DIR

[Michael Vetter]

This naming makes more sense according to the directory structure.
Especially when we later add more paths.

Signed-off-by: Michael Vetter <mvetter@suse.com>
---
 tools/testing/selftests/livepatch/functions.sh | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/livepatch/functions.sh b/tools/testing/selftests/livepatch/functions.sh
index fc4c6a016d38..50361fceff06 100644
--- a/tools/testing/selftests/livepatch/functions.sh
+++ b/tools/testing/selftests/livepatch/functions.sh
@@ -6,7 +6,7 @@
 
 MAX_RETRIES=600
 RETRY_INTERVAL=".1"	# seconds
-KLP_SYSFS_DIR="/sys/kernel/livepatch"
+SYSFS_KLP_DIR="/sys/kernel/livepatch"
 
 # Kselftest framework requirement - SKIP code is 4
 ksft_skip=4
@@ -322,7 +322,7 @@ function check_sysfs_rights() {
 	local rel_path="$1"; shift
 	local expected_rights="$1"; shift
 
-	local path="$KLP_SYSFS_DIR/$mod/$rel_path"
+	local path="$SYSFS_KLP_DIR/$mod/$rel_path"
 	local rights=$(/bin/stat --format '%A' "$path")
 	if test "$rights" != "$expected_rights" ; then
 		die "Unexpected access rights of $path: $expected_rights vs. $rights"
@@ -338,7 +338,7 @@ function check_sysfs_value() {
 	local rel_path="$1"; shift
 	local expected_value="$1"; shift
 
-	local path="$KLP_SYSFS_DIR/$mod/$rel_path"
+	local path="$SYSFS_KLP_DIR/$mod/$rel_path"
 	local value=`cat $path`
 	if test "$value" != "$expected_value" ; then
 		die "Unexpected value in $path: $expected_value vs. $value"
-- 
2.46.1

[PATCH v4 2/3] selftests: livepatch: save and restore kprobe state

[Michael Vetter]

Save the state of /sys/kernel/debug/kprobes/enabled
during setup_config() and restore it during cleanup().

This is in preparation for a future commit that will add a test
that should confirm that we cannot livepatch a kprobed function
if that kprobe has a post handler.

Signed-off-by: Michael Vetter <mvetter@suse.com>
---
 tools/testing/selftests/livepatch/functions.sh | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/livepatch/functions.sh b/tools/testing/selftests/livepatch/functions.sh
index 50361fceff06..91102562db58 100644
--- a/tools/testing/selftests/livepatch/functions.sh
+++ b/tools/testing/selftests/livepatch/functions.sh
@@ -6,7 +6,10 @@
 
 MAX_RETRIES=600
 RETRY_INTERVAL=".1"	# seconds
-SYSFS_KLP_DIR="/sys/kernel/livepatch"
+SYSFS_KERNEL_DIR="/sys/kernel"
+SYSFS_KLP_DIR="$SYSFS_KERNEL_DIR/livepatch"
+SYSFS_DEBUG_DIR="$SYSFS_KERNEL_DIR/debug"
+SYSFS_KPROBES_DIR="$SYSFS_DEBUG_DIR/kprobes"
 
 # Kselftest framework requirement - SKIP code is 4
 ksft_skip=4
@@ -55,22 +58,26 @@ function die() {
 }
 
 function push_config() {
-	DYNAMIC_DEBUG=$(grep '^kernel/livepatch' /sys/kernel/debug/dynamic_debug/control | \
+	DYNAMIC_DEBUG=$(grep '^kernel/livepatch' "$SYSFS_DEBUG_DIR/dynamic_debug/control" | \
 			awk -F'[: ]' '{print "file " $1 " line " $2 " " $4}')
 	FTRACE_ENABLED=$(sysctl --values kernel.ftrace_enabled)
+	KPROBE_ENABLED=$(cat "$SYSFS_KPROBES_DIR/enabled")
 }
 
 function pop_config() {
 	if [[ -n "$DYNAMIC_DEBUG" ]]; then
-		echo -n "$DYNAMIC_DEBUG" > /sys/kernel/debug/dynamic_debug/control
+		echo -n "$DYNAMIC_DEBUG" > "$SYSFS_DEBUG_DIR/dynamic_debug/control"
 	fi
 	if [[ -n "$FTRACE_ENABLED" ]]; then
 		sysctl kernel.ftrace_enabled="$FTRACE_ENABLED" &> /dev/null
 	fi
+	if [[ -n "$KPROBE_ENABLED" ]]; then
+		echo "$KPROBE_ENABLED" > "$SYSFS_KPROBES_DIR/enabled"
+	fi
 }
 
 function set_dynamic_debug() {
-        cat <<-EOF > /sys/kernel/debug/dynamic_debug/control
+        cat <<-EOF > "$SYSFS_DEBUG_DIR/dynamic_debug/control"
 		file kernel/livepatch/* +p
 		func klp_try_switch_task -p
 		EOF
-- 
2.46.1

[PATCH v4 3/3] selftests: livepatch: test livepatching a kprobed function

[Michael Vetter]

The test proves that a function that is being kprobed and uses a
post_handler cannot be livepatched.

Only one ftrace_ops with FTRACE_OPS_FL_IPMODIFY set may be registered
to any given function at a time.

Signed-off-by: Michael Vetter <mvetter@suse.com>
---
 tools/testing/selftests/livepatch/Makefile    |  3 +-
 .../selftests/livepatch/test-kprobe.sh        | 62 +++++++++++++++++++
 .../selftests/livepatch/test_modules/Makefile |  3 +-
 .../livepatch/test_modules/test_klp_kprobe.c  | 38 ++++++++++++
 4 files changed, 104 insertions(+), 2 deletions(-)
 create mode 100755 tools/testing/selftests/livepatch/test-kprobe.sh
 create mode 100644 tools/testing/selftests/livepatch/test_modules/test_klp_kprobe.c

diff --git a/tools/testing/selftests/livepatch/Makefile b/tools/testing/selftests/livepatch/Makefile
index 35418a4790be..a080eb54a215 100644
--- a/tools/testing/selftests/livepatch/Makefile
+++ b/tools/testing/selftests/livepatch/Makefile
@@ -10,7 +10,8 @@ TEST_PROGS := \
 	test-state.sh \
 	test-ftrace.sh \
 	test-sysfs.sh \
-	test-syscall.sh
+	test-syscall.sh \
+	test-kprobe.sh
 
 TEST_FILES := settings
 
diff --git a/tools/testing/selftests/livepatch/test-kprobe.sh b/tools/testing/selftests/livepatch/test-kprobe.sh
new file mode 100755
index 000000000000..115065156016
--- /dev/null
+++ b/tools/testing/selftests/livepatch/test-kprobe.sh
@@ -0,0 +1,62 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2024 SUSE
+# Author: Michael Vetter <mvetter@suse.com>
+
+. $(dirname $0)/functions.sh
+
+MOD_LIVEPATCH=test_klp_livepatch
+MOD_KPROBE=test_klp_kprobe
+
+setup_config
+
+# Kprobe a function and verify that we can't livepatch that same function
+# when it uses a post_handler since only one IPMODIFY maybe be registered
+# to any given function at a time.
+
+start_test "livepatch interaction with kprobed function with post_handler"
+
+echo 1 > "$SYSFS_KPROBES_DIR/enabled"
+
+load_mod $MOD_KPROBE has_post_handler=true
+load_failing_mod $MOD_LIVEPATCH
+unload_mod $MOD_KPROBE
+
+check_result "% insmod test_modules/test_klp_kprobe.ko has_post_handler=true
+% insmod test_modules/$MOD_LIVEPATCH.ko
+livepatch: enabling patch '$MOD_LIVEPATCH'
+livepatch: '$MOD_LIVEPATCH': initializing patching transition
+livepatch: failed to register ftrace handler for function 'cmdline_proc_show' (-16)
+livepatch: failed to patch object 'vmlinux'
+livepatch: failed to enable patch '$MOD_LIVEPATCH'
+livepatch: '$MOD_LIVEPATCH': canceling patching transition, going to unpatch
+livepatch: '$MOD_LIVEPATCH': completing unpatching transition
+livepatch: '$MOD_LIVEPATCH': unpatching complete
+insmod: ERROR: could not insert module test_modules/$MOD_LIVEPATCH.ko: Device or resource busy
+% rmmod test_klp_kprobe"
+
+start_test "livepatch interaction with kprobed function without post_handler"
+
+load_mod $MOD_KPROBE has_post_handler=false
+load_lp $MOD_LIVEPATCH
+
+unload_mod $MOD_KPROBE
+disable_lp $MOD_LIVEPATCH
+unload_lp $MOD_LIVEPATCH
+
+check_result "% insmod test_modules/test_klp_kprobe.ko has_post_handler=false
+% insmod test_modules/$MOD_LIVEPATCH.ko
+livepatch: enabling patch '$MOD_LIVEPATCH'
+livepatch: '$MOD_LIVEPATCH': initializing patching transition
+livepatch: '$MOD_LIVEPATCH': starting patching transition
+livepatch: '$MOD_LIVEPATCH': completing patching transition
+livepatch: '$MOD_LIVEPATCH': patching complete
+% rmmod test_klp_kprobe
+% echo 0 > /sys/kernel/livepatch/$MOD_LIVEPATCH/enabled
+livepatch: '$MOD_LIVEPATCH': initializing unpatching transition
+livepatch: '$MOD_LIVEPATCH': starting unpatching transition
+livepatch: '$MOD_LIVEPATCH': completing unpatching transition
+livepatch: '$MOD_LIVEPATCH': unpatching complete
+% rmmod $MOD_LIVEPATCH"
+
+exit 0
diff --git a/tools/testing/selftests/livepatch/test_modules/Makefile b/tools/testing/selftests/livepatch/test_modules/Makefile
index e6e638c4bcba..939230e571f5 100644
--- a/tools/testing/selftests/livepatch/test_modules/Makefile
+++ b/tools/testing/selftests/livepatch/test_modules/Makefile
@@ -6,11 +6,12 @@ obj-m += test_klp_atomic_replace.o \
 	test_klp_callbacks_demo.o \
 	test_klp_callbacks_demo2.o \
 	test_klp_callbacks_mod.o \
+	test_klp_kprobe.o \
 	test_klp_livepatch.o \
+	test_klp_shadow_vars.o \
 	test_klp_state.o \
 	test_klp_state2.o \
 	test_klp_state3.o \
-	test_klp_shadow_vars.o \
 	test_klp_syscall.o
 
 # Ensure that KDIR exists, otherwise skip the compilation
diff --git a/tools/testing/selftests/livepatch/test_modules/test_klp_kprobe.c b/tools/testing/selftests/livepatch/test_modules/test_klp_kprobe.c
new file mode 100644
index 000000000000..67a8d29012f6
--- /dev/null
+++ b/tools/testing/selftests/livepatch/test_modules/test_klp_kprobe.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2024 Marcos Paulo de Souza <mpdesouza@suse.com>
+// Copyright (C) 2024 Michael Vetter <mvetter@suse.com>
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/kprobes.h>
+
+static bool has_post_handler = true;
+module_param(has_post_handler, bool, 0444);
+
+static void __kprobes post_handler(struct kprobe *p, struct pt_regs *regs,
+				unsigned long flags)
+{
+}
+
+static struct kprobe kp = {
+	.symbol_name = "cmdline_proc_show",
+};
+
+static int __init kprobe_init(void)
+{
+	if (has_post_handler)
+		kp.post_handler = post_handler;
+
+	return register_kprobe(&kp);
+}
+
+static void __exit kprobe_exit(void)
+{
+	unregister_kprobe(&kp);
+}
+
+module_init(kprobe_init)
+module_exit(kprobe_exit)
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Michael Vetter <mvetter@suse.com>");
+MODULE_DESCRIPTION("Livepatch test: kprobe function");
-- 
2.46.1

Re: [PATCH v4 0/3] selftests: livepatch: test livepatching a kprobed function

[Marcos Paulo de Souza]

On Mon, 2024-09-30 at 11:33 +0200, Michael Vetter wrote:
> Thanks to Miroslav, Petr and Marcos for the reviews!

As the only changes were regarding bash nitpicks I keep my review from
earlier patchset, so:

Reviewed-by: Marcos Paulo de Souza <mpdesouza@suse.com>

> 
> V4:
> Use variable for /sys/kernel/debug.
> Be consistent with "" around variables.
> Fix path in commit message to /sys/kernel/debug/kprobes/enabled.
> 
> V3:
> Save and restore kprobe state also when test fails, by integrating it
> into setup_config() and cleanup().
> Rename SYSFS variables in a more logical way.
> Sort test modules in alphabetical order.
> Rename module description.
> 
> V2:
> Save and restore kprobe state.
> 
> Michael Vetter (3):
>   selftests: livepatch: rename KLP_SYSFS_DIR to SYSFS_KLP_DIR
>   selftests: livepatch: save and restore kprobe state
>   selftests: livepatch: test livepatching a kprobed function
> 
>  tools/testing/selftests/livepatch/Makefile    |  3 +-
>  .../testing/selftests/livepatch/functions.sh  | 19 ++++--
>  .../selftests/livepatch/test-kprobe.sh        | 62
> +++++++++++++++++++
>  .../selftests/livepatch/test_modules/Makefile |  3 +-
>  .../livepatch/test_modules/test_klp_kprobe.c  | 38 ++++++++++++
>  5 files changed, 117 insertions(+), 8 deletions(-)
>  create mode 100755 tools/testing/selftests/livepatch/test-kprobe.sh
>  create mode 100644
> tools/testing/selftests/livepatch/test_modules/test_klp_kprobe.c
> 

Re: [PATCH v4 1/3] selftests: livepatch: rename KLP_SYSFS_DIR to SYSFS_KLP_DIR

[Miroslav Benes]

Hi,

On Mon, 30 Sep 2024, Michael Vetter wrote:

> This naming makes more sense according to the directory structure.
> Especially when we later add more paths.
> 
> Signed-off-by: Michael Vetter <mvetter@suse.com>
> ---
>  tools/testing/selftests/livepatch/functions.sh | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/livepatch/functions.sh b/tools/testing/selftests/livepatch/functions.sh
> index fc4c6a016d38..50361fceff06 100644
> --- a/tools/testing/selftests/livepatch/functions.sh
> +++ b/tools/testing/selftests/livepatch/functions.sh
> @@ -6,7 +6,7 @@
>  
>  MAX_RETRIES=600
>  RETRY_INTERVAL=".1"	# seconds
> -KLP_SYSFS_DIR="/sys/kernel/livepatch"
> +SYSFS_KLP_DIR="/sys/kernel/livepatch"
>  
>  # Kselftest framework requirement - SKIP code is 4
>  ksft_skip=4
> @@ -322,7 +322,7 @@ function check_sysfs_rights() {
>  	local rel_path="$1"; shift
>  	local expected_rights="$1"; shift
>  
> -	local path="$KLP_SYSFS_DIR/$mod/$rel_path"
> +	local path="$SYSFS_KLP_DIR/$mod/$rel_path"
>  	local rights=$(/bin/stat --format '%A' "$path")
>  	if test "$rights" != "$expected_rights" ; then
>  		die "Unexpected access rights of $path: $expected_rights vs. $rights"
> @@ -338,7 +338,7 @@ function check_sysfs_value() {
>  	local rel_path="$1"; shift
>  	local expected_value="$1"; shift
>  
> -	local path="$KLP_SYSFS_DIR/$mod/$rel_path"
> +	local path="$SYSFS_KLP_DIR/$mod/$rel_path"
>  	local value=`cat $path`
>  	if test "$value" != "$expected_value" ; then
>  		die "Unexpected value in $path: $expected_value vs. $value"

I am sorry I was not explicit enough previously. There are still 
/sys/kernel/livepatch occurrences in tools/testing/selftest/livepatch/ 
which can be replaced with this new variable. They are there for quite 
some time but it would be really nice if you could replace them all to 
make it consistent since you are touching it.

Thank you,
Miroslav

Re: [PATCH v4 3/3] selftests: livepatch: test livepatching a kprobed function

[Miroslav Benes]

Hi,

On Mon, 30 Sep 2024, Michael Vetter wrote:

> The test proves that a function that is being kprobed and uses a
> post_handler cannot be livepatched.
> 
> Only one ftrace_ops with FTRACE_OPS_FL_IPMODIFY set may be registered
> to any given function at a time.
> 
> Signed-off-by: Michael Vetter <mvetter@suse.com>

since my memory is short, I wondered why you need a separate module to 
register a kprobe for cmdline_proc_show() in vmlinux and why it cannot be 
achieved through tracefs. So... the test ensures that 
FTRACE_OPS_FL_IPMODIFY is exclusive. A kprobe sets FTRACE_OPS_FL_IPMODIFY 
flag if and only if post_handler is not NULL which also indicates a 
situation when regs->ip may be changed in that kprobe. This is something 
which cannot be done in tracefs and hence the module.

It was not clear to me from the changelog.

Miroslav