Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 436 insertions, 0 deletions

diff --git a/rust/syn/buffer.rs b/rust/syn/buffer.rs
new file mode 100644
index 000000000..406f70db3
--- /dev/null
+++ b/rust/syn/buffer.rs
@@ -0,0 +1,436 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! A stably addressed token buffer supporting efficient traversal based on a
+//! cheaply copyable cursor.
+
+// This module is heavily commented as it contains most of the unsafe code in
+// Syn, and caution should be used when editing it. The public-facing interface
+// is 100% safe but the implementation is fragile internally.
+
+use crate::Lifetime;
+use proc_macro2::extra::DelimSpan;
+use proc_macro2::{Delimiter, Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
+use std::cmp::Ordering;
+use std::marker::PhantomData;
+use std::ptr;
+
+/// Internal type which is used instead of `TokenTree` to represent a token tree
+/// within a `TokenBuffer`.
+enum Entry {
+    // Mimicking types from proc-macro.
+    // Group entries contain the offset to the matching End entry.
+    Group(Group, usize),
+    Ident(Ident),
+    Punct(Punct),
+    Literal(Literal),
+    // End entries contain the offset (negative) to the start of the buffer, and
+    // offset (negative) to the matching Group entry.
+    End(isize, isize),
+}
+
+/// A buffer that can be efficiently traversed multiple times, unlike
+/// `TokenStream` which requires a deep copy in order to traverse more than
+/// once.
+pub struct TokenBuffer {
+    // NOTE: Do not implement clone on this - while the current design could be
+    // cloned, other designs which could be desirable may not be cloneable.
+    entries: Box<[Entry]>,
+}
+
+impl TokenBuffer {
+    fn recursive_new(entries: &mut Vec<Entry>, stream: TokenStream) {
+        for tt in stream {
+            match tt {
+                TokenTree::Ident(ident) => entries.push(Entry::Ident(ident)),
+                TokenTree::Punct(punct) => entries.push(Entry::Punct(punct)),
+                TokenTree::Literal(literal) => entries.push(Entry::Literal(literal)),
+                TokenTree::Group(group) => {
+                    let group_start_index = entries.len();
+                    entries.push(Entry::End(0, 0)); // we replace this below
+                    Self::recursive_new(entries, group.stream());
+                    let group_end_index = entries.len();
+                    let group_offset = group_end_index - group_start_index;
+                    entries.push(Entry::End(
+                        -(group_end_index as isize),
+                        -(group_offset as isize),
+                    ));
+                    entries[group_start_index] = Entry::Group(group, group_offset);
+                }
+            }
+        }
+    }
+
+    /// Creates a `TokenBuffer` containing all the tokens from the input
+    /// `proc_macro::TokenStream`.
+    #[cfg(feature = "proc-macro")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "proc-macro")))]
+    pub fn new(stream: proc_macro::TokenStream) -> Self {
+        Self::new2(stream.into())
+    }
+
+    /// Creates a `TokenBuffer` containing all the tokens from the input
+    /// `proc_macro2::TokenStream`.
+    pub fn new2(stream: TokenStream) -> Self {
+        let mut entries = Vec::new();
+        Self::recursive_new(&mut entries, stream);
+        entries.push(Entry::End(-(entries.len() as isize), 0));
+        Self {
+            entries: entries.into_boxed_slice(),
+        }
+    }
+
+    /// Creates a cursor referencing the first token in the buffer and able to
+    /// traverse until the end of the buffer.
+    pub fn begin(&self) -> Cursor {
+        let ptr = self.entries.as_ptr();
+        unsafe { Cursor::create(ptr, ptr.add(self.entries.len() - 1)) }
+    }
+}
+
+/// A cheaply copyable cursor into a `TokenBuffer`.
+///
+/// This cursor holds a shared reference into the immutable data which is used
+/// internally to represent a `TokenStream`, and can be efficiently manipulated
+/// and copied around.
+///
+/// An empty `Cursor` can be created directly, or one may create a `TokenBuffer`
+/// object and get a cursor to its first token with `begin()`.
+pub struct Cursor<'a> {
+    // The current entry which the `Cursor` is pointing at.
+    ptr: *const Entry,
+    // This is the only `Entry::End` object which this cursor is allowed to
+    // point at. All other `End` objects are skipped over in `Cursor::create`.
+    scope: *const Entry,
+    // Cursor is covariant in 'a. This field ensures that our pointers are still
+    // valid.
+    marker: PhantomData<&'a Entry>,
+}
+
+impl<'a> Cursor<'a> {
+    /// Creates a cursor referencing a static empty TokenStream.
+    pub fn empty() -> Self {
+        // It's safe in this situation for us to put an `Entry` object in global
+        // storage, despite it not actually being safe to send across threads
+        // (`Ident` is a reference into a thread-local table). This is because
+        // this entry never includes a `Ident` object.
+        //
+        // This wrapper struct allows us to break the rules and put a `Sync`
+        // object in global storage.
+        struct UnsafeSyncEntry(Entry);
+        unsafe impl Sync for UnsafeSyncEntry {}
+        static EMPTY_ENTRY: UnsafeSyncEntry = UnsafeSyncEntry(Entry::End(0, 0));
+
+        Cursor {
+            ptr: &EMPTY_ENTRY.0,
+            scope: &EMPTY_ENTRY.0,
+            marker: PhantomData,
+        }
+    }
+
+    /// This create method intelligently exits non-explicitly-entered
+    /// `None`-delimited scopes when the cursor reaches the end of them,
+    /// allowing for them to be treated transparently.
+    unsafe fn create(mut ptr: *const Entry, scope: *const Entry) -> Self {
+        // NOTE: If we're looking at a `End`, we want to advance the cursor
+        // past it, unless `ptr == scope`, which means that we're at the edge of
+        // our cursor's scope. We should only have `ptr != scope` at the exit
+        // from None-delimited groups entered with `ignore_none`.
+        while let Entry::End(..) = unsafe { &*ptr } {
+            if ptr::eq(ptr, scope) {
+                break;
+            }
+            ptr = unsafe { ptr.add(1) };
+        }
+
+        Cursor {
+            ptr,
+            scope,
+            marker: PhantomData,
+        }
+    }
+
+    /// Get the current entry.
+    fn entry(self) -> &'a Entry {
+        unsafe { &*self.ptr }
+    }
+
+    /// Bump the cursor to point at the next token after the current one. This
+    /// is undefined behavior if the cursor is currently looking at an
+    /// `Entry::End`.
+    ///
+    /// If the cursor is looking at an `Entry::Group`, the bumped cursor will
+    /// point at the first token in the group (with the same scope end).
+    unsafe fn bump_ignore_group(self) -> Cursor<'a> {
+        unsafe { Cursor::create(self.ptr.offset(1), self.scope) }
+    }
+
+    /// While the cursor is looking at a `None`-delimited group, move it to look
+    /// at the first token inside instead. If the group is empty, this will move
+    /// the cursor past the `None`-delimited group.
+    ///
+    /// WARNING: This mutates its argument.
+    fn ignore_none(&mut self) {
+        while let Entry::Group(group, _) = self.entry() {
+            if group.delimiter() == Delimiter::None {
+                unsafe { *self = self.bump_ignore_group() };
+            } else {
+                break;
+            }
+        }
+    }
+
+    /// Checks whether the cursor is currently pointing at the end of its valid
+    /// scope.
+    pub fn eof(self) -> bool {
+        // We're at eof if we're at the end of our scope.
+        ptr::eq(self.ptr, self.scope)
+    }
+
+    /// If the cursor is pointing at a `Ident`, returns it along with a cursor
+    /// pointing at the next `TokenTree`.
+    pub fn ident(mut self) -> Option<(Ident, Cursor<'a>)> {
+        self.ignore_none();
+        match self.entry() {
+            Entry::Ident(ident) => Some((ident.clone(), unsafe { self.bump_ignore_group() })),
+            _ => None,
+        }
+    }
+
+    /// If the cursor is pointing at a `Punct`, returns it along with a cursor
+    /// pointing at the next `TokenTree`.
+    pub fn punct(mut self) -> Option<(Punct, Cursor<'a>)> {
+        self.ignore_none();
+        match self.entry() {
+            Entry::Punct(punct) if punct.as_char() != '\'' => {
+                Some((punct.clone(), unsafe { self.bump_ignore_group() }))
+            }
+            _ => None,
+        }
+    }
+
+    /// If the cursor is pointing at a `Literal`, return it along with a cursor
+    /// pointing at the next `TokenTree`.
+    pub fn literal(mut self) -> Option<(Literal, Cursor<'a>)> {
+        self.ignore_none();
+        match self.entry() {
+            Entry::Literal(literal) => Some((literal.clone(), unsafe { self.bump_ignore_group() })),
+            _ => None,
+        }
+    }
+
+    /// If the cursor is pointing at a `Lifetime`, returns it along with a
+    /// cursor pointing at the next `TokenTree`.
+    pub fn lifetime(mut self) -> Option<(Lifetime, Cursor<'a>)> {
+        self.ignore_none();
+        match self.entry() {
+            Entry::Punct(punct) if punct.as_char() == '\'' && punct.spacing() == Spacing::Joint => {
+                let next = unsafe { self.bump_ignore_group() };
+                let (ident, rest) = next.ident()?;
+                let lifetime = Lifetime {
+                    apostrophe: punct.span(),
+                    ident,
+                };
+                Some((lifetime, rest))
+            }
+            _ => None,
+        }
+    }
+
+    /// If the cursor is pointing at a `Group` with the given delimiter, returns
+    /// a cursor into that group and one pointing to the next `TokenTree`.
+    pub fn group(mut self, delim: Delimiter) -> Option<(Cursor<'a>, DelimSpan, Cursor<'a>)> {
+        // If we're not trying to enter a none-delimited group, we want to
+        // ignore them. We have to make sure to _not_ ignore them when we want
+        // to enter them, of course. For obvious reasons.
+        if delim != Delimiter::None {
+            self.ignore_none();
+        }
+
+        if let Entry::Group(group, end_offset) = self.entry() {
+            if group.delimiter() == delim {
+                let span = group.delim_span();
+                let end_of_group = unsafe { self.ptr.add(*end_offset) };
+                let inside_of_group = unsafe { Cursor::create(self.ptr.add(1), end_of_group) };
+                let after_group = unsafe { Cursor::create(end_of_group, self.scope) };
+                return Some((inside_of_group, span, after_group));
+            }
+        }
+
+        None
+    }
+
+    /// If the cursor is pointing at a `Group`, returns a cursor into the group
+    /// and one pointing to the next `TokenTree`.
+    pub fn any_group(self) -> Option<(Cursor<'a>, Delimiter, DelimSpan, Cursor<'a>)> {
+        if let Entry::Group(group, end_offset) = self.entry() {
+            let delimiter = group.delimiter();
+            let span = group.delim_span();
+            let end_of_group = unsafe { self.ptr.add(*end_offset) };
+            let inside_of_group = unsafe { Cursor::create(self.ptr.add(1), end_of_group) };
+            let after_group = unsafe { Cursor::create(end_of_group, self.scope) };
+            return Some((inside_of_group, delimiter, span, after_group));
+        }
+
+        None
+    }
+
+    pub(crate) fn any_group_token(self) -> Option<(Group, Cursor<'a>)> {
+        if let Entry::Group(group, end_offset) = self.entry() {
+            let end_of_group = unsafe { self.ptr.add(*end_offset) };
+            let after_group = unsafe { Cursor::create(end_of_group, self.scope) };
+            return Some((group.clone(), after_group));
+        }
+
+        None
+    }
+
+    /// Copies all remaining tokens visible from this cursor into a
+    /// `TokenStream`.
+    pub fn token_stream(self) -> TokenStream {
+        let mut tts = Vec::new();
+        let mut cursor = self;
+        while let Some((tt, rest)) = cursor.token_tree() {
+            tts.push(tt);
+            cursor = rest;
+        }
+        tts.into_iter().collect()
+    }
+
+    /// If the cursor is pointing at a `TokenTree`, returns it along with a
+    /// cursor pointing at the next `TokenTree`.
+    ///
+    /// Returns `None` if the cursor has reached the end of its stream.
+    ///
+    /// This method does not treat `None`-delimited groups as transparent, and
+    /// will return a `Group(None, ..)` if the cursor is looking at one.
+    pub fn token_tree(self) -> Option<(TokenTree, Cursor<'a>)> {
+        let (tree, len) = match self.entry() {
+            Entry::Group(group, end_offset) => (group.clone().into(), *end_offset),
+            Entry::Literal(literal) => (literal.clone().into(), 1),
+            Entry::Ident(ident) => (ident.clone().into(), 1),
+            Entry::Punct(punct) => (punct.clone().into(), 1),
+            Entry::End(..) => return None,
+        };
+
+        let rest = unsafe { Cursor::create(self.ptr.add(len), self.scope) };
+        Some((tree, rest))
+    }
+
+    /// Returns the `Span` of the current token, or `Span::call_site()` if this
+    /// cursor points to eof.
+    pub fn span(mut self) -> Span {
+        match self.entry() {
+            Entry::Group(group, _) => group.span(),
+            Entry::Literal(literal) => literal.span(),
+            Entry::Ident(ident) => ident.span(),
+            Entry::Punct(punct) => punct.span(),
+            Entry::End(_, offset) => {
+                self.ptr = unsafe { self.ptr.offset(*offset) };
+                if let Entry::Group(group, _) = self.entry() {
+                    group.span_close()
+                } else {
+                    Span::call_site()
+                }
+            }
+        }
+    }
+
+    /// Returns the `Span` of the token immediately prior to the position of
+    /// this cursor, or of the current token if there is no previous one.
+    #[cfg(any(feature = "full", feature = "derive"))]
+    pub(crate) fn prev_span(mut self) -> Span {
+        if start_of_buffer(self) < self.ptr {
+            self.ptr = unsafe { self.ptr.offset(-1) };
+        }
+        self.span()
+    }
+
+    /// Skip over the next token that is not a None-delimited group, without
+    /// cloning it. Returns `None` if this cursor points to eof.
+    ///
+    /// This method treats `'lifetimes` as a single token.
+    pub(crate) fn skip(mut self) -> Option<Cursor<'a>> {
+        self.ignore_none();
+
+        let len = match self.entry() {
+            Entry::End(..) => return None,
+
+            // Treat lifetimes as a single tt for the purposes of 'skip'.
+            Entry::Punct(punct) if punct.as_char() == '\'' && punct.spacing() == Spacing::Joint => {
+                match unsafe { &*self.ptr.add(1) } {
+                    Entry::Ident(_) => 2,
+                    _ => 1,
+                }
+            }
+
+            Entry::Group(_, end_offset) => *end_offset,
+            _ => 1,
+        };
+
+        Some(unsafe { Cursor::create(self.ptr.add(len), self.scope) })
+    }
+
+    pub(crate) fn scope_delimiter(self) -> Delimiter {
+        match unsafe { &*self.scope } {
+            Entry::End(_, offset) => match unsafe { &*self.scope.offset(*offset) } {
+                Entry::Group(group, _) => group.delimiter(),
+                _ => Delimiter::None,
+            },
+            _ => unreachable!(),
+        }
+    }
+}
+
+impl<'a> Copy for Cursor<'a> {}
+
+impl<'a> Clone for Cursor<'a> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+impl<'a> Eq for Cursor<'a> {}
+
+impl<'a> PartialEq for Cursor<'a> {
+    fn eq(&self, other: &Self) -> bool {
+        ptr::eq(self.ptr, other.ptr)
+    }
+}
+
+impl<'a> PartialOrd for Cursor<'a> {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        if same_buffer(*self, *other) {
+            Some(cmp_assuming_same_buffer(*self, *other))
+        } else {
+            None
+        }
+    }
+}
+
+pub(crate) fn same_scope(a: Cursor, b: Cursor) -> bool {
+    ptr::eq(a.scope, b.scope)
+}
+
+pub(crate) fn same_buffer(a: Cursor, b: Cursor) -> bool {
+    ptr::eq(start_of_buffer(a), start_of_buffer(b))
+}
+
+fn start_of_buffer(cursor: Cursor) -> *const Entry {
+    unsafe {
+        match &*cursor.scope {
+            Entry::End(offset, _) => cursor.scope.offset(*offset),
+            _ => unreachable!(),
+        }
+    }
+}
+
+pub(crate) fn cmp_assuming_same_buffer(a: Cursor, b: Cursor) -> Ordering {
+    a.ptr.cmp(&b.ptr)
+}
+
+pub(crate) fn open_span_of_group(cursor: Cursor) -> Span {
+    match cursor.entry() {
+        Entry::Group(group, _) => group.span_open(),
+        _ => cursor.span(),
+    }
+}