x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

6 files changed, 1261 insertions, 0 deletions

diff --git a/rust/pin-init/internal/src/diagnostics.rs b/rust/pin-init/internal/src/diagnostics.rs
new file mode 100644
index 000000000..c7d9b3e62
--- /dev/null
+++ b/rust/pin-init/internal/src/diagnostics.rs
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use std::fmt::Display;
+
+use proc_macro2::TokenStream;
+use quote::quote_spanned;
+use syn::{spanned::Spanned, Error};
+
+pub(crate) struct DiagCtxt(TokenStream);
+pub(crate) struct ErrorGuaranteed(());
+
+impl DiagCtxt {
+    pub(crate) fn error(&mut self, span: impl Spanned, msg: impl Display) -> ErrorGuaranteed {
+        let error = Error::new(span.span(), msg);
+        self.0.extend(error.into_compile_error());
+        ErrorGuaranteed(())
+    }
+
+    pub(crate) fn warn(&mut self, span: impl Spanned, msg: impl Display) {
+        // Have the message start on a new line for visual clarity.
+        let msg = format!("\n{}", msg);
+        self.0.extend(quote_spanned!(span.span() =>
+            // Approximate using deprecated warning while `proc_macro_diagnostic` is unstable.
+            const _: () = {
+                #[deprecated = #msg]
+                const fn warn() {}
+                warn();
+            };
+        ));
+    }
+
+    pub(crate) fn with(
+        fun: impl FnOnce(&mut DiagCtxt) -> Result<TokenStream, ErrorGuaranteed>,
+    ) -> TokenStream {
+        let mut dcx = Self(TokenStream::new());
+        match fun(&mut dcx) {
+            Ok(mut stream) => {
+                stream.extend(dcx.0);
+                stream
+            }
+            Err(ErrorGuaranteed(())) => dcx.0,
+        }
+    }
+}
diff --git a/rust/pin-init/internal/src/init.rs b/rust/pin-init/internal/src/init.rs
new file mode 100644
index 000000000..fd0b5ea4a
--- /dev/null
+++ b/rust/pin-init/internal/src/init.rs
@@ -0,0 +1,482 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use proc_macro2::{Span, TokenStream};
+use quote::{format_ident, quote};
+use syn::{
+    braced,
+    parse::{End, Parse},
+    parse_quote,
+    punctuated::Punctuated,
+    spanned::Spanned,
+    token, Attribute, Block, Expr, ExprCall, ExprPath, Ident, Path, Token, Type,
+};
+
+use crate::diagnostics::{DiagCtxt, ErrorGuaranteed};
+
+pub(crate) struct Initializer {
+    attrs: Vec<InitializerAttribute>,
+    this: Option<This>,
+    path: Path,
+    brace_token: token::Brace,
+    fields: Punctuated<InitializerField, Token![,]>,
+    rest: Option<(Token![..], Expr)>,
+    error: Option<(Token![?], Type)>,
+}
+
+struct This {
+    _and_token: Token![&],
+    ident: Ident,
+    _in_token: Token![in],
+}
+
+struct InitializerField {
+    attrs: Vec<Attribute>,
+    kind: InitializerKind,
+}
+
+enum InitializerKind {
+    Value {
+        ident: Ident,
+        value: Option<(Token![:], Expr)>,
+    },
+    Init {
+        ident: Ident,
+        _left_arrow_token: Token![<-],
+        value: Expr,
+    },
+    Code {
+        _underscore_token: Token![_],
+        _colon_token: Token![:],
+        block: Block,
+    },
+}
+
+impl InitializerKind {
+    fn ident(&self) -> Option<&Ident> {
+        match self {
+            Self::Value { ident, .. } | Self::Init { ident, .. } => Some(ident),
+            Self::Code { .. } => None,
+        }
+    }
+}
+
+enum InitializerAttribute {
+    DefaultError(DefaultErrorAttribute),
+}
+
+struct DefaultErrorAttribute {
+    ty: Box<Type>,
+}
+
+pub(crate) fn expand(
+    Initializer {
+        attrs,
+        this,
+        path,
+        brace_token,
+        fields,
+        rest,
+        error,
+    }: Initializer,
+    default_error: Option<&'static str>,
+    pinned: bool,
+    dcx: &mut DiagCtxt,
+) -> Result<TokenStream, ErrorGuaranteed> {
+    let error = error.map_or_else(
+        || {
+            if let Some(default_error) = attrs.iter().fold(None, |acc, attr| {
+                #[expect(irrefutable_let_patterns)]
+                if let InitializerAttribute::DefaultError(DefaultErrorAttribute { ty }) = attr {
+                    Some(ty.clone())
+                } else {
+                    acc
+                }
+            }) {
+                default_error
+            } else if let Some(default_error) = default_error {
+                syn::parse_str(default_error).unwrap()
+            } else {
+                dcx.error(brace_token.span.close(), "expected `? <type>` after `}`");
+                parse_quote!(::core::convert::Infallible)
+            }
+        },
+        |(_, err)| Box::new(err),
+    );
+    let slot = format_ident!("slot");
+    let (has_data_trait, get_data, init_from_closure) = if pinned {
+        (
+            format_ident!("HasPinData"),
+            format_ident!("__pin_data"),
+            format_ident!("pin_init_from_closure"),
+        )
+    } else {
+        (
+            format_ident!("HasInitData"),
+            format_ident!("__init_data"),
+            format_ident!("init_from_closure"),
+        )
+    };
+    let init_kind = get_init_kind(rest, dcx);
+    let zeroable_check = match init_kind {
+        InitKind::Normal => quote!(),
+        InitKind::Zeroing => quote! {
+            // The user specified `..Zeroable::zeroed()` at the end of the list of fields.
+            // Therefore we check if the struct implements `Zeroable` and then zero the memory.
+            // This allows us to also remove the check that all fields are present (since we
+            // already set the memory to zero and that is a valid bit pattern).
+            fn assert_zeroable<T: ?::core::marker::Sized>(_: *mut T)
+            where T: ::pin_init::Zeroable
+            {}
+            // Ensure that the struct is indeed `Zeroable`.
+            assert_zeroable(#slot);
+            // SAFETY: The type implements `Zeroable` by the check above.
+            unsafe { ::core::ptr::write_bytes(#slot, 0, 1) };
+        },
+    };
+    let this = match this {
+        None => quote!(),
+        Some(This { ident, .. }) => quote! {
+            // Create the `this` so it can be referenced by the user inside of the
+            // expressions creating the individual fields.
+            let #ident = unsafe { ::core::ptr::NonNull::new_unchecked(slot) };
+        },
+    };
+    // `mixed_site` ensures that the data is not accessible to the user-controlled code.
+    let data = Ident::new("__data", Span::mixed_site());
+    let init_fields = init_fields(&fields, pinned, &data, &slot);
+    let field_check = make_field_check(&fields, init_kind, &path);
+    Ok(quote! {{
+        // Get the data about fields from the supplied type.
+        // SAFETY: TODO
+        let #data = unsafe {
+            use ::pin_init::__internal::#has_data_trait;
+            // Can't use `<#path as #has_data_trait>::#get_data`, since the user is able to omit
+            // generics (which need to be present with that syntax).
+            #path::#get_data()
+        };
+        // Ensure that `#data` really is of type `#data` and help with type inference:
+        let init = #data.__make_closure::<_, #error>(
+            move |slot| {
+                #zeroable_check
+                #this
+                #init_fields
+                #field_check
+                // SAFETY: we are the `init!` macro that is allowed to call this.
+                Ok(unsafe { ::pin_init::__internal::InitOk::new() })
+            }
+        );
+        let init = move |slot| -> ::core::result::Result<(), #error> {
+            init(slot).map(|__InitOk| ())
+        };
+        // SAFETY: TODO
+        unsafe { ::pin_init::#init_from_closure::<_, #error>(init) }
+    }})
+}
+
+enum InitKind {
+    Normal,
+    Zeroing,
+}
+
+fn get_init_kind(rest: Option<(Token![..], Expr)>, dcx: &mut DiagCtxt) -> InitKind {
+    let Some((dotdot, expr)) = rest else {
+        return InitKind::Normal;
+    };
+    match &expr {
+        Expr::Call(ExprCall { func, args, .. }) if args.is_empty() => match &**func {
+            Expr::Path(ExprPath {
+                attrs,
+                qself: None,
+                path:
+                    Path {
+                        leading_colon: None,
+                        segments,
+                    },
+            }) if attrs.is_empty()
+                && segments.len() == 2
+                && segments[0].ident == "Zeroable"
+                && segments[0].arguments.is_none()
+                && segments[1].ident == "init_zeroed"
+                && segments[1].arguments.is_none() =>
+            {
+                return InitKind::Zeroing;
+            }
+            _ => {}
+        },
+        _ => {}
+    }
+    dcx.error(
+        dotdot.span().join(expr.span()).unwrap_or(expr.span()),
+        "expected nothing or `..Zeroable::init_zeroed()`.",
+    );
+    InitKind::Normal
+}
+
+/// Generate the code that initializes the fields of the struct using the initializers in `field`.
+fn init_fields(
+    fields: &Punctuated<InitializerField, Token![,]>,
+    pinned: bool,
+    data: &Ident,
+    slot: &Ident,
+) -> TokenStream {
+    let mut guards = vec![];
+    let mut guard_attrs = vec![];
+    let mut res = TokenStream::new();
+    for InitializerField { attrs, kind } in fields {
+        let cfgs = {
+            let mut cfgs = attrs.clone();
+            cfgs.retain(|attr| attr.path().is_ident("cfg"));
+            cfgs
+        };
+
+        let ident = match kind {
+            InitializerKind::Value { ident, .. } => ident,
+            InitializerKind::Init { ident, .. } => ident,
+            InitializerKind::Code { block, .. } => {
+                let stmt = &block.stmts;
+                res.extend(quote! {
+                    #(#attrs)*
+                    {
+                        #(#stmt)*
+                    }
+                });
+                continue;
+            }
+        };
+
+        let slot = if pinned {
+            quote! {
+                // SAFETY:
+                // - `slot` is valid and properly aligned.
+                // - `make_field_check` checks that `&raw mut (*slot).#ident` is properly aligned.
+                // - `make_field_check` prevents `#ident` from being used twice, therefore
+                //   `(*slot).#ident` is exclusively accessed and has not been initialized.
+                (unsafe { #data.#ident(#slot) })
+            }
+        } else {
+            quote! {
+                // For `init!()` macro, everything is unpinned.
+                // SAFETY:
+                // - `&raw mut (*slot).#ident` is valid.
+                // - `make_field_check` checks that `&raw mut (*slot).#ident` is properly aligned.
+                // - `make_field_check` prevents `#ident` from being used twice, therefore
+                //   `(*slot).#ident` is exclusively accessed and has not been initialized.
+                (unsafe {
+                    ::pin_init::__internal::Slot::<::pin_init::__internal::Unpinned, _>::new(
+                        &raw mut (*#slot).#ident
+                    )
+                })
+            }
+        };
+
+        // `mixed_site` ensures that the guard is not accessible to the user-controlled code.
+        let guard = format_ident!("__{ident}_guard", span = Span::mixed_site());
+
+        let init = match kind {
+            InitializerKind::Value { ident, value } => {
+                let value = value
+                    .as_ref()
+                    .map(|(_, value)| quote!(#value))
+                    .unwrap_or_else(|| quote!(#ident));
+
+                quote! {
+                    #(#attrs)*
+                    let mut #guard = #slot.write(#value);
+
+                }
+            }
+            InitializerKind::Init { value, .. } => {
+                quote! {
+                    #(#attrs)*
+                    let mut #guard = #slot.init(#value)?;
+                }
+            }
+            InitializerKind::Code { .. } => unreachable!(),
+        };
+
+        res.extend(quote! {
+            #init
+
+            #(#cfgs)*
+            // Allow `non_snake_case` since the same warning is going to be reported for the struct
+            // field.
+            #[allow(unused_variables, non_snake_case)]
+            let #ident = #guard.let_binding();
+        });
+
+        guards.push(guard);
+        guard_attrs.push(cfgs);
+    }
+    quote! {
+        #res
+        // If execution reaches this point, all fields have been initialized. Therefore we can now
+        // dismiss the guards by forgetting them.
+        #(
+            #(#guard_attrs)*
+            ::core::mem::forget(#guards);
+        )*
+    }
+}
+
+/// Generate the check for ensuring that every field has been initialized and aligned.
+fn make_field_check(
+    fields: &Punctuated<InitializerField, Token![,]>,
+    init_kind: InitKind,
+    path: &Path,
+) -> TokenStream {
+    let field_attrs: Vec<_> = fields
+        .iter()
+        .filter_map(|f| f.kind.ident().map(|_| &f.attrs))
+        .collect();
+    let field_name: Vec<_> = fields.iter().filter_map(|f| f.kind.ident()).collect();
+    let zeroing_trailer = match init_kind {
+        InitKind::Normal => None,
+        InitKind::Zeroing => Some(quote! {
+            ..::core::mem::zeroed()
+        }),
+    };
+    quote! {
+        #[allow(unreachable_code)]
+        // We use unreachable code to perform field checks. They're still checked by the compiler.
+        // SAFETY: this code is never executed.
+        let _ = || unsafe {
+            // Create references to ensure that the initialized field is properly aligned.
+            // Unaligned fields will cause the compiler to emit E0793. We do not support
+            // unaligned fields since `Init::__init` requires an aligned pointer; the call to
+            // `ptr::write` for value-initialization case has the same requirement.
+            #(
+                #(#field_attrs)*
+                let _ = &(*slot).#field_name;
+            )*
+
+            // If the zeroing trailer is not present, this checks that all fields have been
+            // mentioned exactly once. If the zeroing trailer is present, all missing fields will be
+            // zeroed, so this checks that all fields have been mentioned at most once. The use of
+            // struct initializer will still generate very natural error messages for any misuse.
+            ::core::ptr::write(slot, #path {
+                #(
+                    #(#field_attrs)*
+                    #field_name: loop {},
+                )*
+                #zeroing_trailer
+            })
+        };
+    }
+}
+
+impl Parse for Initializer {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let attrs = input.call(Attribute::parse_outer)?;
+        let this = input.peek(Token![&]).then(|| input.parse()).transpose()?;
+        let path = input.parse()?;
+        let content;
+        let brace_token = braced!(content in input);
+        let mut fields = Punctuated::new();
+        loop {
+            let lh = content.lookahead1();
+            if lh.peek(End) || lh.peek(Token![..]) {
+                break;
+            } else if lh.peek(Ident) || lh.peek(Token![_]) || lh.peek(Token![#]) {
+                fields.push_value(content.parse()?);
+                let lh = content.lookahead1();
+                if lh.peek(End) {
+                    break;
+                } else if lh.peek(Token![,]) {
+                    fields.push_punct(content.parse()?);
+                } else {
+                    return Err(lh.error());
+                }
+            } else {
+                return Err(lh.error());
+            }
+        }
+        let rest = content
+            .peek(Token![..])
+            .then(|| Ok::<_, syn::Error>((content.parse()?, content.parse()?)))
+            .transpose()?;
+        let error = input
+            .peek(Token![?])
+            .then(|| Ok::<_, syn::Error>((input.parse()?, input.parse()?)))
+            .transpose()?;
+        let attrs = attrs
+            .into_iter()
+            .map(|a| {
+                if a.path().is_ident("default_error") {
+                    a.parse_args::<DefaultErrorAttribute>()
+                        .map(InitializerAttribute::DefaultError)
+                } else {
+                    Err(syn::Error::new_spanned(a, "unknown initializer attribute"))
+                }
+            })
+            .collect::<Result<Vec<_>, _>>()?;
+        Ok(Self {
+            attrs,
+            this,
+            path,
+            brace_token,
+            fields,
+            rest,
+            error,
+        })
+    }
+}
+
+impl Parse for DefaultErrorAttribute {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        Ok(Self { ty: input.parse()? })
+    }
+}
+
+impl Parse for This {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        Ok(Self {
+            _and_token: input.parse()?,
+            ident: input.parse()?,
+            _in_token: input.parse()?,
+        })
+    }
+}
+
+impl Parse for InitializerField {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let attrs = input.call(Attribute::parse_outer)?;
+        Ok(Self {
+            attrs,
+            kind: input.parse()?,
+        })
+    }
+}
+
+impl Parse for InitializerKind {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let lh = input.lookahead1();
+        if lh.peek(Token![_]) {
+            Ok(Self::Code {
+                _underscore_token: input.parse()?,
+                _colon_token: input.parse()?,
+                block: input.parse()?,
+            })
+        } else if lh.peek(Ident) {
+            let ident = input.parse()?;
+            let lh = input.lookahead1();
+            if lh.peek(Token![<-]) {
+                Ok(Self::Init {
+                    ident,
+                    _left_arrow_token: input.parse()?,
+                    value: input.parse()?,
+                })
+            } else if lh.peek(Token![:]) {
+                Ok(Self::Value {
+                    ident,
+                    value: Some((input.parse()?, input.parse()?)),
+                })
+            } else if lh.peek(Token![,]) || lh.peek(End) {
+                Ok(Self::Value { ident, value: None })
+            } else {
+                Err(lh.error())
+            }
+        } else {
+            Err(lh.error())
+        }
+    }
+}
diff --git a/rust/pin-init/internal/src/lib.rs b/rust/pin-init/internal/src/lib.rs
new file mode 100644
index 000000000..60d5093f3
--- /dev/null
+++ b/rust/pin-init/internal/src/lib.rs
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+// When fixdep scans this, it will find this string `CONFIG_RUSTC_VERSION_TEXT`
+// and thus add a dependency on `include/config/RUSTC_VERSION_TEXT`, which is
+// touched by Kconfig when the version string from the compiler changes.
+
+//! `pin-init` proc macros.
+
+// Documentation is done in the pin-init crate instead.
+#![allow(missing_docs)]
+
+use proc_macro::TokenStream;
+use syn::parse_macro_input;
+
+use crate::diagnostics::DiagCtxt;
+
+mod diagnostics;
+mod init;
+mod pin_data;
+mod pinned_drop;
+mod zeroable;
+
+#[proc_macro_attribute]
+pub fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
+    let args = parse_macro_input!(args);
+    let input = parse_macro_input!(input);
+    DiagCtxt::with(|dcx| pin_data::pin_data(args, input, dcx)).into()
+}
+
+#[proc_macro_attribute]
+pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
+    let args = parse_macro_input!(args);
+    let input = parse_macro_input!(input);
+    DiagCtxt::with(|dcx| pinned_drop::pinned_drop(args, input, dcx)).into()
+}
+
+#[proc_macro_derive(Zeroable)]
+pub fn derive_zeroable(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input);
+    DiagCtxt::with(|dcx| zeroable::derive(input, dcx)).into()
+}
+
+#[proc_macro_derive(MaybeZeroable)]
+pub fn maybe_derive_zeroable(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input);
+    DiagCtxt::with(|dcx| zeroable::maybe_derive(input, dcx)).into()
+}
+#[proc_macro]
+pub fn init(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input);
+    DiagCtxt::with(|dcx| init::expand(input, Some("::core::convert::Infallible"), false, dcx))
+        .into()
+}
+
+#[proc_macro]
+pub fn pin_init(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input);
+    DiagCtxt::with(|dcx| init::expand(input, Some("::core::convert::Infallible"), true, dcx)).into()
+}
diff --git a/rust/pin-init/internal/src/pin_data.rs b/rust/pin-init/internal/src/pin_data.rs
new file mode 100644
index 000000000..ff194d275
--- /dev/null
+++ b/rust/pin-init/internal/src/pin_data.rs
@@ -0,0 +1,537 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote, ToTokens};
+use syn::{
+    parse::{End, Nothing, Parse},
+    parse_quote, parse_quote_spanned,
+    spanned::Spanned,
+    visit_mut::VisitMut,
+    Field, Fields, Generics, Ident, Item, PathSegment, Type, TypePath, Visibility, WhereClause,
+};
+
+use crate::diagnostics::{DiagCtxt, ErrorGuaranteed};
+
+pub(crate) mod kw {
+    syn::custom_keyword!(PinnedDrop);
+}
+
+pub(crate) enum Args {
+    Nothing(Nothing),
+    #[allow(dead_code)]
+    PinnedDrop(kw::PinnedDrop),
+}
+
+impl Parse for Args {
+    fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> {
+        let lh = input.lookahead1();
+        if lh.peek(End) {
+            input.parse().map(Self::Nothing)
+        } else if lh.peek(kw::PinnedDrop) {
+            input.parse().map(Self::PinnedDrop)
+        } else {
+            Err(lh.error())
+        }
+    }
+}
+
+impl ToTokens for Args {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        match self {
+            Self::Nothing(_) => (),
+            Self::PinnedDrop(kw) => kw.to_tokens(tokens),
+        }
+    }
+}
+
+struct FieldInfo<'a> {
+    field: &'a Field,
+    pinned: bool,
+}
+
+pub(crate) fn pin_data(
+    args: Args,
+    input: Item,
+    dcx: &mut DiagCtxt,
+) -> Result<TokenStream, ErrorGuaranteed> {
+    let mut struct_ = match input {
+        Item::Struct(struct_) => struct_,
+        Item::Enum(enum_) => {
+            return Err(dcx.error(
+                enum_.enum_token,
+                "`#[pin_data]` only supports structs for now",
+            ));
+        }
+        Item::Union(union) => {
+            return Err(dcx.error(
+                union.union_token,
+                "`#[pin_data]` only supports structs for now",
+            ));
+        }
+        rest => {
+            return Err(dcx.error(
+                rest,
+                "`#[pin_data]` can only be applied to struct, enum and union definitions",
+            ));
+        }
+    };
+
+    // Handling cfg can gets very complicated, especially for tuple structs. Therefore, resolve all
+    // field cfgs first before continuing.
+    //
+    // We need to perform this after parsing so we can reliably detect field cfgs.
+    for (field_idx, field) in struct_.fields.iter_mut().enumerate() {
+        let cfg: Vec<_> = field
+            .attrs
+            .iter()
+            .filter(|a| a.path().is_ident("cfg"))
+            .map(|a| {
+                a.parse_args::<TokenStream>()
+                    .expect("parse as token stream cannot fail")
+            })
+            .collect();
+
+        if cfg.is_empty() {
+            continue;
+        }
+
+        field.attrs.retain(|a| !a.path().is_ident("cfg"));
+        let cfg_true_struct = quote!(#struct_);
+
+        let punctuated = match &mut struct_.fields {
+            Fields::Named(fields) => &mut fields.named,
+            Fields::Unnamed(fields) => &mut fields.unnamed,
+            Fields::Unit => unreachable!(),
+        };
+        *punctuated = std::mem::take(punctuated)
+            .into_pairs()
+            .enumerate()
+            .filter(|&(i, _)| i != field_idx)
+            .map(|(_, p)| p)
+            .collect();
+        let cfg_false_struct = quote!(#struct_);
+
+        // Resolve one field at a time until we've got no more field cfgs.
+        //
+        // This is linear time because macro invocations with false cfg will not be expanded.
+        return Ok(quote!(
+            #[cfg(all(#(#cfg,)*))]
+            #[::pin_init::pin_data(#args)]
+            #cfg_true_struct
+
+            #[cfg(not(all(#(#cfg,)*)))]
+            #[::pin_init::pin_data(#args)]
+            #cfg_false_struct
+        ));
+    }
+
+    // The generics might contain the `Self` type. Since this macro will define a new type with the
+    // same generics and bounds, this poses a problem: `Self` will refer to the new type as opposed
+    // to this struct definition. Therefore we have to replace `Self` with the concrete name.
+    let mut replacer = {
+        let name = &struct_.ident;
+        let (_, ty_generics, _) = struct_.generics.split_for_impl();
+        SelfReplacer(parse_quote!(#name #ty_generics))
+    };
+    replacer.visit_generics_mut(&mut struct_.generics);
+    replacer.visit_fields_mut(&mut struct_.fields);
+
+    let fields: Vec<FieldInfo<'_>> = struct_
+        .fields
+        .iter_mut()
+        .map(|field| {
+            let len = field.attrs.len();
+            field.attrs.retain(|a| !a.path().is_ident("pin"));
+            let pinned_count = len - field.attrs.len();
+            if pinned_count > 1 {
+                dcx.error(&field, "#[pin] attribute specified more than once");
+            }
+
+            assert!(
+                !field.attrs.iter().any(|a| a.path().is_ident("cfg")),
+                "cfgs should be all resolved at this point"
+            );
+
+            FieldInfo {
+                field: &*field,
+                pinned: pinned_count != 0,
+            }
+        })
+        .collect();
+
+    for field in &fields {
+        let ident = field.field.ident.as_ref().unwrap();
+
+        if !field.pinned && is_phantom_pinned(&field.field.ty) {
+            dcx.warn(
+                field.field,
+                format!(
+                    "The field `{ident}` of type `PhantomPinned` only has an effect \
+                    if it has the `#[pin]` attribute",
+                ),
+            );
+        }
+    }
+
+    let unpin_impl = generate_unpin_impl(&struct_.ident, &struct_.generics, &fields);
+    let drop_impl = generate_drop_impl(&struct_.ident, &struct_.generics, args);
+    let projections =
+        generate_projections(&struct_.vis, &struct_.ident, &struct_.generics, &fields);
+    let the_pin_data =
+        generate_the_pin_data(&struct_.vis, &struct_.ident, &struct_.generics, &fields);
+
+    Ok(quote! {
+        #struct_
+        #projections
+        // We put the rest into this const item, because it then will not be accessible to anything
+        // outside.
+        const _: () = {
+            #the_pin_data
+            #unpin_impl
+            #drop_impl
+        };
+    })
+}
+
+fn is_phantom_pinned(ty: &Type) -> bool {
+    match ty {
+        Type::Path(TypePath { qself: None, path }) => {
+            // Cannot possibly refer to `PhantomPinned` (except alias, but that's on the user).
+            if path.segments.len() > 3 {
+                return false;
+            }
+            // If there is a `::`, then the path needs to be `::core::marker::PhantomPinned` or
+            // `::std::marker::PhantomPinned`.
+            if path.leading_colon.is_some() && path.segments.len() != 3 {
+                return false;
+            }
+            let expected: Vec<&[&str]> = vec![&["PhantomPinned"], &["marker"], &["core", "std"]];
+            for (actual, expected) in path.segments.iter().rev().zip(expected) {
+                if !actual.arguments.is_empty() || expected.iter().all(|e| actual.ident != e) {
+                    return false;
+                }
+            }
+            true
+        }
+        _ => false,
+    }
+}
+
+fn generate_unpin_impl(
+    ident: &Ident,
+    generics: &Generics,
+    fields: &[FieldInfo<'_>],
+) -> TokenStream {
+    let (_, ty_generics, _) = generics.split_for_impl();
+    let mut generics_with_pin_lt = generics.clone();
+    generics_with_pin_lt.params.insert(0, parse_quote!('__pin));
+    generics_with_pin_lt.make_where_clause();
+    let (
+        impl_generics_with_pin_lt,
+        ty_generics_with_pin_lt,
+        Some(WhereClause {
+            where_token,
+            predicates,
+        }),
+    ) = generics_with_pin_lt.split_for_impl()
+    else {
+        unreachable!()
+    };
+    let pinned_fields = fields.iter().filter(|f| f.pinned).map(|f| {
+        let ident = f.field.ident.as_ref().unwrap();
+        let ty = &f.field.ty;
+        quote!(
+            #ident: #ty
+        )
+    });
+    quote! {
+        // This struct will be used for the unpin analysis. It is needed, because only structurally
+        // pinned fields are relevant whether the struct should implement `Unpin`.
+        #[allow(
+            dead_code, // The fields below are never used.
+            non_snake_case // The warning will be emitted on the struct definition.
+        )]
+        struct __Unpin #generics_with_pin_lt
+        #where_token
+            #predicates
+        {
+            __phantom_pin: ::pin_init::__internal::PhantomInvariantLifetime<'__pin>,
+            __phantom: ::pin_init::__internal::PhantomInvariant<#ident #ty_generics>,
+            #(#pinned_fields),*
+        }
+
+        #[doc(hidden)]
+        impl #impl_generics_with_pin_lt ::core::marker::Unpin for #ident #ty_generics
+        #where_token
+            __Unpin #ty_generics_with_pin_lt: ::core::marker::Unpin,
+            #predicates
+        {}
+    }
+}
+
+fn generate_drop_impl(ident: &Ident, generics: &Generics, args: Args) -> TokenStream {
+    let (impl_generics, ty_generics, whr) = generics.split_for_impl();
+    let has_pinned_drop = matches!(args, Args::PinnedDrop(_));
+    // We need to disallow normal `Drop` implementation, the exact behavior depends on whether
+    // `PinnedDrop` was specified in `args`.
+    if has_pinned_drop {
+        // When `PinnedDrop` was specified we just implement `Drop` and delegate.
+        quote! {
+            impl #impl_generics ::core::ops::Drop for #ident #ty_generics
+                #whr
+            {
+                fn drop(&mut self) {
+                    // SAFETY: Since this is a destructor, `self` will not move after this function
+                    // terminates, since it is inaccessible.
+                    let pinned = unsafe { ::core::pin::Pin::new_unchecked(self) };
+                    // SAFETY: Since this is a drop function, we can create this token to call the
+                    // pinned destructor of this type.
+                    let token = unsafe { ::pin_init::__internal::OnlyCallFromDrop::new() };
+                    ::pin_init::PinnedDrop::drop(pinned, token);
+                }
+            }
+        }
+    } else {
+        // When no `PinnedDrop` was specified, then we have to prevent implementing drop.
+        quote! {
+            // We prevent this by creating a trait that will be implemented for all types implementing
+            // `Drop`. Additionally we will implement this trait for the struct leading to a conflict,
+            // if it also implements `Drop`
+            trait MustNotImplDrop {}
+            impl<T: ::core::ops::Drop + ?::core::marker::Sized> MustNotImplDrop for T {}
+            impl #impl_generics MustNotImplDrop for #ident #ty_generics
+                #whr
+            {}
+            // We also take care to prevent users from writing a useless `PinnedDrop` implementation.
+            // They might implement `PinnedDrop` correctly for the struct, but forget to give
+            // `PinnedDrop` as the parameter to `#[pin_data]`.
+            trait UselessPinnedDropImpl_you_need_to_specify_PinnedDrop {}
+            impl<T: ::pin_init::PinnedDrop + ?::core::marker::Sized>
+                UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for T {}
+            impl #impl_generics
+                UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for #ident #ty_generics
+                #whr
+            {}
+        }
+    }
+}
+
+fn generate_projections(
+    vis: &Visibility,
+    ident: &Ident,
+    generics: &Generics,
+    fields: &[FieldInfo<'_>],
+) -> TokenStream {
+    let (impl_generics, ty_generics, _) = generics.split_for_impl();
+    let mut generics_with_pin_lt = generics.clone();
+    generics_with_pin_lt.params.insert(0, parse_quote!('__pin));
+    let (_, ty_generics_with_pin_lt, whr) = generics_with_pin_lt.split_for_impl();
+    let projection = format_ident!("{ident}Projection");
+    let this = format_ident!("this");
+
+    let (fields_decl, fields_proj): (Vec<_>, Vec<_>) = fields
+        .iter()
+        .map(|field| {
+            let Field { vis, ident, ty, .. } = &field.field;
+
+            let ident = ident
+                .as_ref()
+                .expect("only structs with named fields are supported");
+            if field.pinned {
+                (
+                    quote!(
+                        #vis #ident: ::core::pin::Pin<&'__pin mut #ty>,
+                    ),
+                    quote!(
+                        // SAFETY: this field is structurally pinned.
+                        #ident: unsafe { ::core::pin::Pin::new_unchecked(&mut #this.#ident) },
+                    ),
+                )
+            } else {
+                (
+                    quote!(
+                        #vis #ident: &'__pin mut #ty,
+                    ),
+                    quote!(
+                        #ident: &mut #this.#ident,
+                    ),
+                )
+            }
+        })
+        .collect();
+    let structurally_pinned_fields_docs = fields
+        .iter()
+        .filter(|f| f.pinned)
+        .map(|f| format!(" - `{}`", f.field.ident.as_ref().unwrap()));
+    let not_structurally_pinned_fields_docs = fields
+        .iter()
+        .filter(|f| !f.pinned)
+        .map(|f| format!(" - `{}`", f.field.ident.as_ref().unwrap()));
+    let docs = format!(" Pin-projections of [`{ident}`]");
+    quote! {
+        #[doc = #docs]
+        // Allow `non_snake_case` since the same warning will be emitted on
+        // the struct definition.
+        #[allow(dead_code, non_snake_case)]
+        #[doc(hidden)]
+        #vis struct #projection #generics_with_pin_lt
+            #whr
+        {
+            #(#fields_decl)*
+            ___pin_phantom_data: ::core::marker::PhantomData<&'__pin mut ()>,
+        }
+
+        impl #impl_generics #ident #ty_generics
+            #whr
+        {
+            /// Pin-projects all fields of `Self`.
+            ///
+            /// These fields are structurally pinned:
+            #(#[doc = #structurally_pinned_fields_docs])*
+            ///
+            /// These fields are **not** structurally pinned:
+            #(#[doc = #not_structurally_pinned_fields_docs])*
+            #[inline]
+            #vis fn project<'__pin>(
+                self: ::core::pin::Pin<&'__pin mut Self>,
+            ) -> #projection #ty_generics_with_pin_lt {
+                // SAFETY: we only give access to `&mut` for fields not structurally pinned.
+                let #this = unsafe { ::core::pin::Pin::get_unchecked_mut(self) };
+                #projection {
+                    #(#fields_proj)*
+                    ___pin_phantom_data: ::core::marker::PhantomData,
+                }
+            }
+        }
+    }
+}
+
+fn generate_the_pin_data(
+    vis: &Visibility,
+    struct_name: &Ident,
+    generics: &Generics,
+    fields: &[FieldInfo<'_>],
+) -> TokenStream {
+    let (impl_generics, ty_generics, whr) = generics.split_for_impl();
+
+    // For every field, we create an initializing projection function according to its projection
+    // type. If a field is structurally pinned, we create a `Slot` with `Pinned` which must be
+    // initialized via `PinInit`; if it is not structurally pinned, then we create a `Slot` with
+    // `Unpinned` which allows initialization via `Init`.
+    let field_accessors = fields
+        .iter()
+        .map(|f| {
+            let Field { vis, ident, ty, .. } = f.field;
+
+            let field_name = ident
+                .as_ref()
+                .expect("only structs with named fields are supported");
+            let pin_marker = if f.pinned {
+                quote!(Pinned)
+            } else {
+                quote!(Unpinned)
+            };
+            quote! {
+                /// # Safety
+                ///
+                /// - `slot` is valid and properly aligned.
+                /// - `(*slot).#field_name` is properly aligned.
+                /// - `(*slot).#field_name` points to uninitialized and exclusively accessed
+                ///   memory.
+                // Allow `non_snake_case` since the same warning will be emitted on
+                // the struct definition.
+                #[allow(non_snake_case)]
+                #[inline(always)]
+                #vis unsafe fn #field_name(
+                    self,
+                    slot: *mut #struct_name #ty_generics,
+                ) -> ::pin_init::__internal::Slot<::pin_init::__internal::#pin_marker, #ty> {
+                    // SAFETY:
+                    // - If `#pin_marker` is `Pinned`, the corresponding field is structurally
+                    //   pinned.
+                    // - Other safety requirements follows the safety requirement.
+                    unsafe { ::pin_init::__internal::Slot::new(&raw mut (*slot).#field_name) }
+                }
+            }
+        })
+        .collect::<TokenStream>();
+    quote! {
+        // We declare this struct which will host all of the projection function for our type. It
+        // will be invariant over all generic parameters which are inherited from the struct.
+        #[doc(hidden)]
+        #vis struct __ThePinData #generics
+            #whr
+        {
+            __phantom: ::pin_init::__internal::PhantomInvariant<#struct_name #ty_generics>,
+        }
+
+        impl #impl_generics ::core::clone::Clone for __ThePinData #ty_generics
+            #whr
+        {
+            #[inline]
+            fn clone(&self) -> Self { *self }
+        }
+
+        impl #impl_generics ::core::marker::Copy for __ThePinData #ty_generics
+            #whr
+        {}
+
+        #[allow(dead_code)] // Some functions might never be used and private.
+        impl #impl_generics __ThePinData #ty_generics
+            #whr
+        {
+            /// Type inference helper function.
+            #[inline(always)]
+            #vis fn __make_closure<__F, __E>(self, f: __F) -> __F
+            where
+                __F: FnOnce(*mut #struct_name #ty_generics) ->
+                    ::core::result::Result<::pin_init::__internal::InitOk, __E>,
+            {
+                f
+            }
+
+            #field_accessors
+        }
+
+        // SAFETY: We have added the correct projection functions above to `__ThePinData` and
+        // we also use the least restrictive generics possible.
+        unsafe impl #impl_generics ::pin_init::__internal::HasPinData for #struct_name #ty_generics
+            #whr
+        {
+            type PinData = __ThePinData #ty_generics;
+
+            #[inline]
+            unsafe fn __pin_data() -> Self::PinData {
+                __ThePinData { __phantom: ::pin_init::__internal::PhantomInvariant::new() }
+            }
+        }
+    }
+}
+
+struct SelfReplacer(PathSegment);
+
+impl VisitMut for SelfReplacer {
+    fn visit_path_mut(&mut self, i: &mut syn::Path) {
+        if i.is_ident("Self") {
+            let span = i.span();
+            let seg = &self.0;
+            *i = parse_quote_spanned!(span=> #seg);
+        } else {
+            syn::visit_mut::visit_path_mut(self, i);
+        }
+    }
+
+    fn visit_path_segment_mut(&mut self, seg: &mut PathSegment) {
+        if seg.ident == "Self" {
+            let span = seg.span();
+            let this = &self.0;
+            *seg = parse_quote_spanned!(span=> #this);
+        } else {
+            syn::visit_mut::visit_path_segment_mut(self, seg);
+        }
+    }
+
+    fn visit_item_mut(&mut self, _: &mut Item) {
+        // Do not descend into items, since items reset/change what `Self` refers to.
+    }
+}
diff --git a/rust/pin-init/internal/src/pinned_drop.rs b/rust/pin-init/internal/src/pinned_drop.rs
new file mode 100644
index 000000000..a20ac314c
--- /dev/null
+++ b/rust/pin-init/internal/src/pinned_drop.rs
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{parse::Nothing, parse_quote, spanned::Spanned, ImplItem, ItemImpl, Token};
+
+use crate::diagnostics::{DiagCtxt, ErrorGuaranteed};
+
+pub(crate) fn pinned_drop(
+    _args: Nothing,
+    mut input: ItemImpl,
+    dcx: &mut DiagCtxt,
+) -> Result<TokenStream, ErrorGuaranteed> {
+    if let Some(unsafety) = input.unsafety {
+        dcx.error(unsafety, "implementing `PinnedDrop` is safe");
+    }
+    input.unsafety = Some(Token![unsafe](input.impl_token.span));
+    match &mut input.trait_ {
+        Some((not, path, _for)) => {
+            if let Some(not) = not {
+                dcx.error(not, "cannot implement `!PinnedDrop`");
+            }
+            for (seg, expected) in path
+                .segments
+                .iter()
+                .rev()
+                .zip(["PinnedDrop", "pin_init", ""])
+            {
+                if expected.is_empty() || seg.ident != expected {
+                    dcx.error(seg, "bad import path for `PinnedDrop`");
+                }
+                if !seg.arguments.is_none() {
+                    dcx.error(&seg.arguments, "unexpected arguments for `PinnedDrop` path");
+                }
+            }
+            *path = parse_quote!(::pin_init::PinnedDrop);
+        }
+        None => {
+            let span = input
+                .impl_token
+                .span
+                .join(input.self_ty.span())
+                .unwrap_or(input.impl_token.span);
+            dcx.error(
+                span,
+                "expected `impl ... PinnedDrop for ...`, got inherent impl",
+            );
+        }
+    }
+    for item in &mut input.items {
+        if let ImplItem::Fn(fn_item) = item {
+            if fn_item.sig.ident == "drop" {
+                fn_item
+                    .sig
+                    .inputs
+                    .push(parse_quote!(_: ::pin_init::__internal::OnlyCallFromDrop));
+            }
+        }
+    }
+    Ok(quote!(#input))
+}
diff --git a/rust/pin-init/internal/src/zeroable.rs b/rust/pin-init/internal/src/zeroable.rs
new file mode 100644
index 000000000..b11feaeb1
--- /dev/null
+++ b/rust/pin-init/internal/src/zeroable.rs
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{parse_quote, Data, DeriveInput, Field, Fields};
+
+use crate::{diagnostics::ErrorGuaranteed, DiagCtxt};
+
+pub(crate) fn derive(
+    input: DeriveInput,
+    dcx: &mut DiagCtxt,
+) -> Result<TokenStream, ErrorGuaranteed> {
+    let fields = match input.data {
+        Data::Struct(data_struct) => data_struct.fields,
+        Data::Union(data_union) => Fields::Named(data_union.fields),
+        Data::Enum(data_enum) => {
+            return Err(dcx.error(data_enum.enum_token, "cannot derive `Zeroable` for an enum"));
+        }
+    };
+    let name = input.ident;
+    let mut generics = input.generics;
+    for param in generics.type_params_mut() {
+        param.bounds.insert(0, parse_quote!(::pin_init::Zeroable));
+    }
+    let (impl_gen, ty_gen, whr) = generics.split_for_impl();
+    let field_type = fields.iter().map(|field| &field.ty);
+    Ok(quote! {
+        // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero.
+        #[automatically_derived]
+        unsafe impl #impl_gen ::pin_init::Zeroable for #name #ty_gen
+            #whr
+        {}
+        const _: () = {
+            fn assert_zeroable<T: ?::core::marker::Sized + ::pin_init::Zeroable>() {}
+            fn ensure_zeroable #impl_gen ()
+                #whr
+            {
+                #(
+                    assert_zeroable::<#field_type>();
+                )*
+            }
+        };
+    })
+}
+
+pub(crate) fn maybe_derive(
+    input: DeriveInput,
+    dcx: &mut DiagCtxt,
+) -> Result<TokenStream, ErrorGuaranteed> {
+    let fields = match input.data {
+        Data::Struct(data_struct) => data_struct.fields,
+        Data::Union(data_union) => Fields::Named(data_union.fields),
+        Data::Enum(data_enum) => {
+            return Err(dcx.error(data_enum.enum_token, "cannot derive `Zeroable` for an enum"));
+        }
+    };
+    let name = input.ident;
+    let mut generics = input.generics;
+    for param in generics.type_params_mut() {
+        param.bounds.insert(0, parse_quote!(::pin_init::Zeroable));
+    }
+    for Field { ty, .. } in fields {
+        generics
+            .make_where_clause()
+            .predicates
+            // the `for<'__dummy>` HRTB makes this not error without the `trivial_bounds`
+            // feature <https://github.com/rust-lang/rust/issues/48214#issuecomment-2557829956>.
+            .push(parse_quote!(#ty: for<'__dummy> ::pin_init::Zeroable));
+    }
+    let (impl_gen, ty_gen, whr) = generics.split_for_impl();
+    Ok(quote! {
+        // SAFETY: Every field type implements `Zeroable` and padding bytes may be zero.
+        #[automatically_derived]
+        unsafe impl #impl_gen ::pin_init::Zeroable for #name #ty_gen
+            #whr
+        {}
+    })
+}