Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

3 files changed, 297 insertions, 0 deletions

diff --git a/Documentation/driver-api/early-userspace/buffer-format.rst b/Documentation/driver-api/early-userspace/buffer-format.rst
new file mode 100644
index 000000000..4597a9110
--- /dev/null
+++ b/Documentation/driver-api/early-userspace/buffer-format.rst
@@ -0,0 +1,132 @@
+=======================
+initramfs buffer format
+=======================
+
+Al Viro, H. Peter Anvin
+
+With kernel 2.5.x, the old "initial ramdisk" protocol was complemented
+with an "initial ramfs" protocol.  The initramfs content is passed
+using the same memory buffer protocol used by initrd, but the content
+is different.  The initramfs buffer contains an archive which is
+expanded into a ramfs filesystem; this document details the initramfs
+buffer format.
+
+The initramfs buffer format is based around the "newc" or "crc" CPIO
+formats, and can be created with the cpio(1) utility.  The cpio
+archive can be compressed using gzip(1), or any other algorithm provided
+via CONFIG_DECOMPRESS_*.  One valid version of an initramfs buffer is
+thus a single .cpio.gz file.
+
+The full format of the initramfs buffer is defined by the following
+grammar, where::
+
+	*	is used to indicate "0 or more occurrences of"
+	(|)	indicates alternatives
+	+	indicates concatenation
+	GZIP()	indicates gzip compression of the operand
+	BZIP2()	indicates bzip2 compression of the operand
+	LZMA()	indicates lzma compression of the operand
+	XZ()	indicates xz compression of the operand
+	LZO()	indicates lzo compression of the operand
+	LZ4()	indicates lz4 compression of the operand
+	ZSTD()	indicates zstd compression of the operand
+	ALGN(n)	means padding with null bytes to an n-byte boundary
+
+	initramfs := ("\0" | cpio_archive | cpio_compressed_archive)*
+
+	cpio_compressed_archive := (GZIP(cpio_archive) | BZIP2(cpio_archive)
+		| LZMA(cpio_archive) | XZ(cpio_archive) | LZO(cpio_archive)
+		| LZ4(cpio_archive) | ZSTD(cpio_archive))
+
+	cpio_archive := cpio_file* + (<nothing> | cpio_trailer)
+
+	cpio_file := ALGN(4) + cpio_header + filename + "\0" + ALGN(4) + data
+
+	cpio_trailer := ALGN(4) + cpio_header + "TRAILER!!!\0" + ALGN(4)
+
+
+In human terms, the initramfs buffer contains a collection of
+compressed and/or uncompressed cpio archives (in the "newc" or "crc"
+formats); arbitrary amounts zero bytes (for padding) can be added
+between members.
+
+The cpio "TRAILER!!!" entry (cpio end-of-archive) is optional, but is
+not ignored; see "handling of hard links" below.
+
+The structure of the cpio_header is as follows (all fields contain
+hexadecimal ASCII numbers fully padded with '0' on the left to the
+full width of the field, for example, the integer 4780 is represented
+by the ASCII string "000012ac"):
+
+============= ================== ==============================================
+Field name    Field size	 Meaning
+============= ================== ==============================================
+c_magic	      6 bytes		 The string "070701" or "070702"
+c_ino	      8 bytes		 File inode number
+c_mode	      8 bytes		 File mode and permissions
+c_uid	      8 bytes		 File uid
+c_gid	      8 bytes		 File gid
+c_nlink	      8 bytes		 Number of links
+c_mtime	      8 bytes		 Modification time
+c_filesize    8 bytes		 Size of data field
+c_maj	      8 bytes		 Major part of file device number
+c_min	      8 bytes		 Minor part of file device number
+c_rmaj	      8 bytes		 Major part of device node reference
+c_rmin	      8 bytes		 Minor part of device node reference
+c_namesize    8 bytes		 Length of filename, including final \0
+c_chksum      8 bytes		 Checksum of data field if c_magic is 070702;
+				 otherwise zero
+============= ================== ==============================================
+
+The c_mode field matches the contents of st_mode returned by stat(2)
+on Linux, and encodes the file type and file permissions.
+
+c_mtime is ignored unless CONFIG_INITRAMFS_PRESERVE_MTIME=y is set.
+
+The c_filesize should be zero for any file which is not a regular file
+or symlink.
+
+c_namesize may account for more than one trailing '\0', as long as the
+value doesn't exceed PATH_MAX.  This can be useful for ensuring that a
+subsequent file data segment is aligned, e.g. to a filesystem block
+boundary.
+
+The c_chksum field contains a simple 32-bit unsigned sum of all the
+bytes in the data field.  cpio(1) refers to this as "crc", which is
+clearly incorrect (a cyclic redundancy check is a different and
+significantly stronger integrity check), however, this is the
+algorithm used.
+
+If the filename is "TRAILER!!!" this is actually an end-of-archive
+marker; the c_filesize for an end-of-archive marker must be zero.
+
+
+Handling of hard links
+======================
+
+When a nondirectory with c_nlink > 1 is seen, the (c_maj,c_min,c_ino)
+tuple is looked up in a tuple buffer.  If not found, it is entered in
+the tuple buffer and the entry is created as usual; if found, a hard
+link rather than a second copy of the file is created.  It is not
+necessary (but permitted) to include a second copy of the file
+contents; if the file contents is not included, the c_filesize field
+should be set to zero to indicate no data section follows.  If data is
+present, the previous instance of the file is overwritten; this allows
+the data-carrying instance of a file to occur anywhere in the sequence
+(GNU cpio is reported to attach the data to the last instance of a
+file only.)
+
+c_filesize must not be zero for a symlink.
+
+When a "TRAILER!!!" end-of-archive marker is seen, the tuple buffer is
+reset.  This permits archives which are generated independently to be
+concatenated.
+
+To combine file data from different sources (without having to
+regenerate the (c_maj,c_min,c_ino) fields), therefore, either one of
+the following techniques can be used:
+
+a) Separate the different file data sources with a "TRAILER!!!"
+   end-of-archive marker, or
+
+b) Make sure c_nlink == 1 for all nondirectory entries.
diff --git a/Documentation/driver-api/early-userspace/early_userspace_support.rst b/Documentation/driver-api/early-userspace/early_userspace_support.rst
new file mode 100644
index 000000000..60d1e1bc9
--- /dev/null
+++ b/Documentation/driver-api/early-userspace/early_userspace_support.rst
@@ -0,0 +1,154 @@
+=======================
+Early userspace support
+=======================
+
+Last update: 2004-12-20 tlh
+
+
+"Early userspace" is a set of libraries and programs that provide
+various pieces of functionality that are important enough to be
+available while a Linux kernel is coming up, but that don't need to be
+run inside the kernel itself.
+
+It consists of several major infrastructure components:
+
+- gen_init_cpio, a program that builds a cpio-format archive
+  containing a root filesystem image.  This archive is compressed, and
+  the compressed image is linked into the kernel image.
+- initramfs, a chunk of code that unpacks the compressed cpio image
+  midway through the kernel boot process.
+- klibc, a userspace C library, currently packaged separately, that is
+  optimized for correctness and small size.
+
+The cpio file format used by initramfs is the "newc" (aka "cpio -H newc")
+format, and is documented in the file "buffer-format.txt".  There are
+two ways to add an early userspace image: specify an existing cpio
+archive to be used as the image or have the kernel build process build
+the image from specifications.
+
+CPIO ARCHIVE method
+-------------------
+
+You can create a cpio archive that contains the early userspace image.
+Your cpio archive should be specified in CONFIG_INITRAMFS_SOURCE and it
+will be used directly.  Only a single cpio file may be specified in
+CONFIG_INITRAMFS_SOURCE and directory and file names are not allowed in
+combination with a cpio archive.
+
+IMAGE BUILDING method
+---------------------
+
+The kernel build process can also build an early userspace image from
+source parts rather than supplying a cpio archive.  This method provides
+a way to create images with root-owned files even though the image was
+built by an unprivileged user.
+
+The image is specified as one or more sources in
+CONFIG_INITRAMFS_SOURCE.  Sources can be either directories or files -
+cpio archives are *not* allowed when building from sources.
+
+A source directory will have it and all of its contents packaged.  The
+specified directory name will be mapped to '/'.  When packaging a
+directory, limited user and group ID translation can be performed.
+INITRAMFS_ROOT_UID can be set to a user ID that needs to be mapped to
+user root (0).  INITRAMFS_ROOT_GID can be set to a group ID that needs
+to be mapped to group root (0).
+
+A source file must be directives in the format required by the
+usr/gen_init_cpio utility (run 'usr/gen_init_cpio -h' to get the
+file format).  The directives in the file will be passed directly to
+usr/gen_init_cpio.
+
+When a combination of directories and files are specified then the
+initramfs image will be an aggregate of all of them.  In this way a user
+can create a 'root-image' directory and install all files into it.
+Because device-special files cannot be created by a unprivileged user,
+special files can be listed in a 'root-files' file.  Both 'root-image'
+and 'root-files' can be listed in CONFIG_INITRAMFS_SOURCE and a complete
+early userspace image can be built by an unprivileged user.
+
+As a technical note, when directories and files are specified, the
+entire CONFIG_INITRAMFS_SOURCE is passed to
+usr/gen_initramfs.sh.  This means that CONFIG_INITRAMFS_SOURCE
+can really be interpreted as any legal argument to
+gen_initramfs.sh.  If a directory is specified as an argument then
+the contents are scanned, uid/gid translation is performed, and
+usr/gen_init_cpio file directives are output.  If a file is
+specified as an argument to usr/gen_initramfs.sh then the
+contents of the file are simply copied to the output.  All of the output
+directives from directory scanning and file contents copying are
+processed by usr/gen_init_cpio.
+
+See also 'usr/gen_initramfs.sh -h'.
+
+Where's this all leading?
+=========================
+
+The klibc distribution contains some of the necessary software to make
+early userspace useful.  The klibc distribution is currently
+maintained separately from the kernel.
+
+You can obtain somewhat infrequent snapshots of klibc from
+https://www.kernel.org/pub/linux/libs/klibc/
+
+For active users, you are better off using the klibc git
+repository, at https://git.kernel.org/?p=libs/klibc/klibc.git
+
+The standalone klibc distribution currently provides three components,
+in addition to the klibc library:
+
+- ipconfig, a program that configures network interfaces.  It can
+  configure them statically, or use DHCP to obtain information
+  dynamically (aka "IP autoconfiguration").
+- nfsmount, a program that can mount an NFS filesystem.
+- kinit, the "glue" that uses ipconfig and nfsmount to replace the old
+  support for IP autoconfig, mount a filesystem over NFS, and continue
+  system boot using that filesystem as root.
+
+kinit is built as a single statically linked binary to save space.
+
+Eventually, several more chunks of kernel functionality will hopefully
+move to early userspace:
+
+- Almost all of init/do_mounts* (the beginning of this is already in
+  place)
+- ACPI table parsing
+- Insert unwieldy subsystem that doesn't really need to be in kernel
+  space here
+
+If kinit doesn't meet your current needs and you've got bytes to burn,
+the klibc distribution includes a small Bourne-compatible shell (ash)
+and a number of other utilities, so you can replace kinit and build
+custom initramfs images that meet your needs exactly.
+
+For questions and help, you can sign up for the early userspace
+mailing list at https://www.zytor.com/mailman/listinfo/klibc
+
+How does it work?
+=================
+
+The kernel has currently 3 ways to mount the root filesystem:
+
+a) all required device and filesystem drivers compiled into the kernel, no
+   initrd.  init/main.c:init() will call prepare_namespace() to mount the
+   final root filesystem, based on the root= option and optional init= to run
+   some other init binary than listed at the end of init/main.c:init().
+
+b) some device and filesystem drivers built as modules and stored in an
+   initrd.  The initrd must contain a binary '/linuxrc' which is supposed to
+   load these driver modules.  It is also possible to mount the final root
+   filesystem via linuxrc and use the pivot_root syscall.  The initrd is
+   mounted and executed via prepare_namespace().
+
+c) using initramfs.  The call to prepare_namespace() must be skipped.
+   This means that a binary must do all the work.  Said binary can be stored
+   into initramfs either via modifying usr/gen_init_cpio.c or via the new
+   initrd format, an cpio archive.  It must be called "/init".  This binary
+   is responsible to do all the things prepare_namespace() would do.
+
+   To maintain backwards compatibility, the /init binary will only run if it
+   comes via an initramfs cpio archive.  If this is not the case,
+   init/main.c:init() will run prepare_namespace() to mount the final root
+   and exec one of the predefined init binaries.
+
+Bryan O'Sullivan <bos@serpentine.com>
diff --git a/Documentation/driver-api/early-userspace/index.rst b/Documentation/driver-api/early-userspace/index.rst
new file mode 100644
index 000000000..ff4594712
--- /dev/null
+++ b/Documentation/driver-api/early-userspace/index.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+Early Userspace
+===============
+
+.. toctree::
+    :maxdepth: 1
+
+    early_userspace_support
+    buffer-format