[for-linus][PATCH 0/5] tracing: Updates for 5.16-rc5

[for-linus][PATCH 0/5] tracing: Updates for 5.16-rc5

[Steven Rostedt]

Ftrace and tracefs fixes:

 - Have tracefs honor the gid mount option

 - Have new files in tracefs inherit the parent ownership

 - Have direct_ops unregister when it has no more functions

 - Properly clean up the ops when unregistering multi direct ops

 - Add a sample module to test the multiple direct ops

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
ftrace/urgent

Head SHA1: 72a86f97053fc70c8cfa6bdef3154bda8a811041


Jiri Olsa (3):
      ftrace: Use direct_ops hash in unregister_ftrace_direct
      ftrace: Add cleanup to unregister_ftrace_direct_multi
      ftrace/samples: Add module to test multi direct modify interface

Steven Rostedt (VMware) (2):
      tracefs: Have new files inherit the ownership of their parent
      tracefs: Set all files to the same group ownership as the mount option

----
 fs/tracefs/inode.c                          |  76 ++++++++++++++
 kernel/trace/ftrace.c                       |   8 +-
 samples/ftrace/Makefile                     |   1 +
 samples/ftrace/ftrace-direct-multi-modify.c | 152 ++++++++++++++++++++++++++++
 4 files changed, 236 insertions(+), 1 deletion(-)
 create mode 100644 samples/ftrace/ftrace-direct-multi-modify.c

[for-linus][PATCH 1/5] tracefs: Have new files inherit the ownership of their parent

[Steven Rostedt]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

If directories in tracefs have their ownership changed, then any new files
and directories that are created under those directories should inherit
the ownership of the director they are created in.

Link: https://lkml.kernel.org/r/20211208075720.4855d180@gandalf.local.home

Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Yabin Cui <yabinc@google.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: stable@vger.kernel.org
Fixes: 4282d60689d4f ("tracefs: Add new tracefs file system")
Reported-by: Kalesh Singh <kaleshsingh@google.com>
Reported: https://lore.kernel.org/all/CAC_TJve8MMAv+H_NdLSJXZUSoxOEq2zB_pVaJ9p=7H6Bu3X76g@mail.gmail.com/
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 fs/tracefs/inode.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 925a621b432e..06cf0534cc60 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -414,6 +414,8 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode,
 	inode->i_mode = mode;
 	inode->i_fop = fops ? fops : &tracefs_file_operations;
 	inode->i_private = data;
+	inode->i_uid = d_inode(dentry->d_parent)->i_uid;
+	inode->i_gid = d_inode(dentry->d_parent)->i_gid;
 	d_instantiate(dentry, inode);
 	fsnotify_create(dentry->d_parent->d_inode, dentry);
 	return end_creating(dentry);
@@ -436,6 +438,8 @@ static struct dentry *__create_dir(const char *name, struct dentry *parent,
 	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUSR| S_IRGRP | S_IXUSR | S_IXGRP;
 	inode->i_op = ops;
 	inode->i_fop = &simple_dir_operations;
+	inode->i_uid = d_inode(dentry->d_parent)->i_uid;
+	inode->i_gid = d_inode(dentry->d_parent)->i_gid;
 
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
-- 
2.33.0

[for-linus][PATCH 2/5] tracefs: Set all files to the same group ownership as the mount option

[Steven Rostedt]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

As people have been asking to allow non-root processes to have access to
the tracefs directory, it was considered best to only allow groups to have
access to the directory, where it is easier to just set the tracefs file
system to a specific group (as other would be too dangerous), and that way
the admins could pick which processes would have access to tracefs.

Unfortunately, this broke tooling on Android that expected the other bit
to be set. For some special cases, for non-root tools to trace the system,
tracefs would be mounted and change the permissions of the top level
directory which gave access to all running tasks permission to the
tracing directory. Even though this would be dangerous to do in a
production environment, for testing environments this can be useful.

Now with the new changes to not allow other (which is still the proper
thing to do), it breaks the testing tooling. Now more code needs to be
loaded on the system to change ownership of the tracing directory.

The real solution is to have tracefs honor the gid=xxx option when
mounting. That is,

(tracing group tracing has value 1003)

 mount -t tracefs -o gid=1003 tracefs /sys/kernel/tracing

should have it that all files in the tracing directory should be of the
given group.

Copy the logic from d_walk() from dcache.c and simplify it for the mount
case of tracefs if gid is set. All the files in tracefs will be walked and
their group will be set to the value passed in.

Link: https://lkml.kernel.org/r/20211207171729.2a54e1b3@gandalf.local.home

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reported-by: Kalesh Singh <kaleshsingh@google.com>
Reported-by: Yabin Cui <yabinc@google.com>
Fixes: 49d67e445742 ("tracefs: Have tracefs directories not set OTH permission bits by default")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 fs/tracefs/inode.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 06cf0534cc60..3616839c5c4b 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -161,6 +161,77 @@ struct tracefs_fs_info {
 	struct tracefs_mount_opts mount_opts;
 };
 
+static void change_gid(struct dentry *dentry, kgid_t gid)
+{
+	if (!dentry->d_inode)
+		return;
+	dentry->d_inode->i_gid = gid;
+}
+
+/*
+ * Taken from d_walk, but without he need for handling renames.
+ * Nothing can be renamed while walking the list, as tracefs
+ * does not support renames. This is only called when mounting
+ * or remounting the file system, to set all the files to
+ * the given gid.
+ */
+static void set_gid(struct dentry *parent, kgid_t gid)
+{
+	struct dentry *this_parent;
+	struct list_head *next;
+
+	this_parent = parent;
+	spin_lock(&this_parent->d_lock);
+
+	change_gid(this_parent, gid);
+repeat:
+	next = this_parent->d_subdirs.next;
+resume:
+	while (next != &this_parent->d_subdirs) {
+		struct list_head *tmp = next;
+		struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
+		next = tmp->next;
+
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+
+		change_gid(dentry, gid);
+
+		if (!list_empty(&dentry->d_subdirs)) {
+			spin_unlock(&this_parent->d_lock);
+			spin_release(&dentry->d_lock.dep_map, _RET_IP_);
+			this_parent = dentry;
+			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
+			goto repeat;
+		}
+		spin_unlock(&dentry->d_lock);
+	}
+	/*
+	 * All done at this level ... ascend and resume the search.
+	 */
+	rcu_read_lock();
+ascend:
+	if (this_parent != parent) {
+		struct dentry *child = this_parent;
+		this_parent = child->d_parent;
+
+		spin_unlock(&child->d_lock);
+		spin_lock(&this_parent->d_lock);
+
+		/* go into the first sibling still alive */
+		do {
+			next = child->d_child.next;
+			if (next == &this_parent->d_subdirs)
+				goto ascend;
+			child = list_entry(next, struct dentry, d_child);
+		} while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
+		rcu_read_unlock();
+		goto resume;
+	}
+	rcu_read_unlock();
+	spin_unlock(&this_parent->d_lock);
+	return;
+}
+
 static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
 {
 	substring_t args[MAX_OPT_ARGS];
@@ -193,6 +264,7 @@ static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
 			if (!gid_valid(gid))
 				return -EINVAL;
 			opts->gid = gid;
+			set_gid(tracefs_mount->mnt_root, gid);
 			break;
 		case Opt_mode:
 			if (match_octal(&args[0], &option))
-- 
2.33.0

[for-linus][PATCH 3/5] ftrace: Use direct_ops hash in unregister_ftrace_direct

[Steven Rostedt]

From: Jiri Olsa <jolsa@redhat.com>

Now when we have *direct_multi interface the direct_functions
hash is no longer owned just by direct_ops. It's also used by
any other ftrace_ops passed to *direct_multi interface.

Thus to find out that we are unregistering the last function
from direct_ops, we need to check directly direct_ops's hash.

Link: https://lkml.kernel.org/r/20211206182032.87248-2-jolsa@kernel.org

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Fixes: f64dd4627ec6 ("ftrace: Add multi direct register/unregister interface")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 30bc880c3849..7f0594e28226 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5217,6 +5217,7 @@ int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
 {
 	struct ftrace_direct_func *direct;
 	struct ftrace_func_entry *entry;
+	struct ftrace_hash *hash;
 	int ret = -ENODEV;
 
 	mutex_lock(&direct_mutex);
@@ -5225,7 +5226,8 @@ int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
 	if (!entry)
 		goto out_unlock;
 
-	if (direct_functions->count == 1)
+	hash = direct_ops.func_hash->filter_hash;
+	if (hash->count == 1)
 		unregister_ftrace_function(&direct_ops);
 
 	ret = ftrace_set_filter_ip(&direct_ops, ip, 1, 0);
-- 
2.33.0

[for-linus][PATCH 4/5] ftrace: Add cleanup to unregister_ftrace_direct_multi

[Steven Rostedt]

From: Jiri Olsa <jolsa@redhat.com>

Adding ops cleanup to unregister_ftrace_direct_multi,
so it can be reused in another register call.

Link: https://lkml.kernel.org/r/20211206182032.87248-3-jolsa@kernel.org

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Fixes: f64dd4627ec6 ("ftrace: Add multi direct register/unregister interface")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7f0594e28226..be5f6b32a012 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5542,6 +5542,10 @@ int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
 	err = unregister_ftrace_function(ops);
 	remove_direct_functions_hash(hash, addr);
 	mutex_unlock(&direct_mutex);
+
+	/* cleanup for possible another register call */
+	ops->func = NULL;
+	ops->trampoline = 0;
 	return err;
 }
 EXPORT_SYMBOL_GPL(unregister_ftrace_direct_multi);
-- 
2.33.0

[for-linus][PATCH 5/5] ftrace/samples: Add module to test multi direct modify interface

[Steven Rostedt]

From: Jiri Olsa <jolsa@redhat.com>

Adding ftrace-direct-multi-modify.ko kernel module that uses
modify_ftrace_direct_multi API. The core functionality is taken
from ftrace-direct-modify.ko kernel module and changed to fit
multi direct interface.

The init function creates kthread that periodically calls
modify_ftrace_direct_multi to change the trampoline address
for the direct ftrace_ops. The ftrace trace_pipe then shows
trace from both trampolines.

Link: https://lkml.kernel.org/r/20211206182032.87248-4-jolsa@kernel.org

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 samples/ftrace/Makefile                     |   1 +
 samples/ftrace/ftrace-direct-multi-modify.c | 152 ++++++++++++++++++++
 2 files changed, 153 insertions(+)
 create mode 100644 samples/ftrace/ftrace-direct-multi-modify.c

diff --git a/samples/ftrace/Makefile b/samples/ftrace/Makefile
index b9198e2eef28..faf8cdb79c5f 100644
--- a/samples/ftrace/Makefile
+++ b/samples/ftrace/Makefile
@@ -4,6 +4,7 @@ obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct.o
 obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-too.o
 obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-modify.o
 obj-$(CONFIG_SAMPLE_FTRACE_DIRECT_MULTI) += ftrace-direct-multi.o
+obj-$(CONFIG_SAMPLE_FTRACE_DIRECT_MULTI) += ftrace-direct-multi-modify.o
 
 CFLAGS_sample-trace-array.o := -I$(src)
 obj-$(CONFIG_SAMPLE_TRACE_ARRAY) += sample-trace-array.o
diff --git a/samples/ftrace/ftrace-direct-multi-modify.c b/samples/ftrace/ftrace-direct-multi-modify.c
new file mode 100644
index 000000000000..91bc42a7adb9
--- /dev/null
+++ b/samples/ftrace/ftrace-direct-multi-modify.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/module.h>
+#include <linux/kthread.h>
+#include <linux/ftrace.h>
+#include <asm/asm-offsets.h>
+
+void my_direct_func1(unsigned long ip)
+{
+	trace_printk("my direct func1 ip %lx\n", ip);
+}
+
+void my_direct_func2(unsigned long ip)
+{
+	trace_printk("my direct func2 ip %lx\n", ip);
+}
+
+extern void my_tramp1(void *);
+extern void my_tramp2(void *);
+
+#ifdef CONFIG_X86_64
+
+asm (
+"	.pushsection    .text, \"ax\", @progbits\n"
+"	.type		my_tramp1, @function\n"
+"	.globl		my_tramp1\n"
+"   my_tramp1:"
+"	pushq %rbp\n"
+"	movq %rsp, %rbp\n"
+"	pushq %rdi\n"
+"	movq 8(%rbp), %rdi\n"
+"	call my_direct_func1\n"
+"	popq %rdi\n"
+"	leave\n"
+"	ret\n"
+"	.size		my_tramp1, .-my_tramp1\n"
+"	.type		my_tramp2, @function\n"
+"\n"
+"	.globl		my_tramp2\n"
+"   my_tramp2:"
+"	pushq %rbp\n"
+"	movq %rsp, %rbp\n"
+"	pushq %rdi\n"
+"	movq 8(%rbp), %rdi\n"
+"	call my_direct_func2\n"
+"	popq %rdi\n"
+"	leave\n"
+"	ret\n"
+"	.size		my_tramp2, .-my_tramp2\n"
+"	.popsection\n"
+);
+
+#endif /* CONFIG_X86_64 */
+
+#ifdef CONFIG_S390
+
+asm (
+"       .pushsection    .text, \"ax\", @progbits\n"
+"       .type           my_tramp1, @function\n"
+"       .globl          my_tramp1\n"
+"   my_tramp1:"
+"       lgr             %r1,%r15\n"
+"       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
+"       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
+"       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
+"       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
+"       lgr             %r2,%r0\n"
+"       brasl           %r14,my_direct_func1\n"
+"       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
+"       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
+"       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
+"       lgr             %r1,%r0\n"
+"       br              %r1\n"
+"       .size           my_tramp1, .-my_tramp1\n"
+"\n"
+"       .type           my_tramp2, @function\n"
+"       .globl          my_tramp2\n"
+"   my_tramp2:"
+"       lgr             %r1,%r15\n"
+"       stmg            %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
+"       stg             %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
+"       aghi            %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
+"       stg             %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
+"       lgr             %r2,%r0\n"
+"       brasl           %r14,my_direct_func2\n"
+"       aghi            %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
+"       lmg             %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
+"       lg              %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
+"       lgr             %r1,%r0\n"
+"       br              %r1\n"
+"       .size           my_tramp2, .-my_tramp2\n"
+"       .popsection\n"
+);
+
+#endif /* CONFIG_S390 */
+
+static unsigned long my_tramp = (unsigned long)my_tramp1;
+static unsigned long tramps[2] = {
+	(unsigned long)my_tramp1,
+	(unsigned long)my_tramp2,
+};
+
+static struct ftrace_ops direct;
+
+static int simple_thread(void *arg)
+{
+	static int t;
+	int ret = 0;
+
+	while (!kthread_should_stop()) {
+		set_current_state(TASK_INTERRUPTIBLE);
+		schedule_timeout(2 * HZ);
+
+		if (ret)
+			continue;
+		t ^= 1;
+		ret = modify_ftrace_direct_multi(&direct, tramps[t]);
+		if (!ret)
+			my_tramp = tramps[t];
+		WARN_ON_ONCE(ret);
+	}
+
+	return 0;
+}
+
+static struct task_struct *simple_tsk;
+
+static int __init ftrace_direct_multi_init(void)
+{
+	int ret;
+
+	ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
+	ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
+
+	ret = register_ftrace_direct_multi(&direct, my_tramp);
+
+	if (!ret)
+		simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
+	return ret;
+}
+
+static void __exit ftrace_direct_multi_exit(void)
+{
+	kthread_stop(simple_tsk);
+	unregister_ftrace_direct_multi(&direct, my_tramp);
+}
+
+module_init(ftrace_direct_multi_init);
+module_exit(ftrace_direct_multi_exit);
+
+MODULE_AUTHOR("Jiri Olsa");
+MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()");
+MODULE_LICENSE("GPL");
-- 
2.33.0

Re: [for-linus][PATCH 5/5] ftrace/samples: Add module to test multi direct modify interface

[Heiko Carstens]

On Thu, Dec 09, 2021 at 10:29:13AM -0500, Steven Rostedt wrote:
> From: Jiri Olsa <jolsa@redhat.com>
> 
> Adding ftrace-direct-multi-modify.ko kernel module that uses
> modify_ftrace_direct_multi API. The core functionality is taken
> from ftrace-direct-modify.ko kernel module and changed to fit
> multi direct interface.
> 
> The init function creates kthread that periodically calls
> modify_ftrace_direct_multi to change the trampoline address
> for the direct ftrace_ops. The ftrace trace_pipe then shows
> trace from both trampolines.
> 
> Link: https://lkml.kernel.org/r/20211206182032.87248-4-jolsa@kernel.org
> 
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Heiko Carstens <hca@linux.ibm.com>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
>  samples/ftrace/Makefile                     |   1 +
>  samples/ftrace/ftrace-direct-multi-modify.c | 152 ++++++++++++++++++++
>  2 files changed, 153 insertions(+)
>  create mode 100644 samples/ftrace/ftrace-direct-multi-modify.c

FWIW, for the s390 bits in here:

Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Tested-by: Heiko Carstens <hca@linux.ibm.com>

Re: [for-linus][PATCH 5/5] ftrace/samples: Add module to test multi direct modify interface

[Steven Rostedt]

On Thu, 9 Dec 2021 18:50:57 +0100
Heiko Carstens <hca@linux.ibm.com> wrote:

> FWIW, for the s390 bits in here:
> 
> Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
> Tested-by: Heiko Carstens <hca@linux.ibm.com>

Thanks! I'll update the tags. (one of the reasons I post patches before
sending a pull request).

-- Steve