From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions 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) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- rust/syn/data.rs | 426 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 426 insertions(+) create mode 100644 rust/syn/data.rs (limited to 'rust/syn/data.rs') diff --git a/rust/syn/data.rs b/rust/syn/data.rs new file mode 100644 index 000000000..c32c1366c --- /dev/null +++ b/rust/syn/data.rs @@ -0,0 +1,426 @@ +// SPDX-License-Identifier: Apache-2.0 OR MIT + +use crate::attr::Attribute; +use crate::expr::{Expr, Index, Member}; +use crate::ident::Ident; +use crate::punctuated::{self, Punctuated}; +use crate::restriction::{FieldMutability, Visibility}; +use crate::token; +use crate::ty::Type; + +ast_struct! { + /// An enum variant. + #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))] + pub struct Variant { + pub attrs: Vec, + + /// Name of the variant. + pub ident: Ident, + + /// Content stored in the variant. + pub fields: Fields, + + /// Explicit discriminant: `Variant = 1` + pub discriminant: Option<(Token![=], Expr)>, + } +} + +ast_enum_of_structs! { + /// Data stored within an enum variant or struct. + /// + /// # Syntax tree enum + /// + /// This type is a [syntax tree enum]. + /// + /// [syntax tree enum]: crate::expr::Expr#syntax-tree-enums + #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))] + pub enum Fields { + /// Named fields of a struct or struct variant such as `Point { x: f64, + /// y: f64 }`. + Named(FieldsNamed), + + /// Unnamed fields of a tuple struct or tuple variant such as `Some(T)`. + Unnamed(FieldsUnnamed), + + /// Unit struct or unit variant such as `None`. + Unit, + } +} + +ast_struct! { + /// Named fields of a struct or struct variant such as `Point { x: f64, + /// y: f64 }`. + #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))] + pub struct FieldsNamed { + pub brace_token: token::Brace, + pub named: Punctuated, + } +} + +ast_struct! { + /// Unnamed fields of a tuple struct or tuple variant such as `Some(T)`. + #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))] + pub struct FieldsUnnamed { + pub paren_token: token::Paren, + pub unnamed: Punctuated, + } +} + +impl Fields { + /// Get an iterator over the borrowed [`Field`] items in this object. This + /// iterator can be used to iterate over a named or unnamed struct or + /// variant's fields uniformly. + pub fn iter(&self) -> punctuated::Iter { + match self { + Fields::Unit => crate::punctuated::empty_punctuated_iter(), + Fields::Named(f) => f.named.iter(), + Fields::Unnamed(f) => f.unnamed.iter(), + } + } + + /// Get an iterator over the mutably borrowed [`Field`] items in this + /// object. This iterator can be used to iterate over a named or unnamed + /// struct or variant's fields uniformly. + pub fn iter_mut(&mut self) -> punctuated::IterMut { + match self { + Fields::Unit => crate::punctuated::empty_punctuated_iter_mut(), + Fields::Named(f) => f.named.iter_mut(), + Fields::Unnamed(f) => f.unnamed.iter_mut(), + } + } + + /// Returns the number of fields. + pub fn len(&self) -> usize { + match self { + Fields::Unit => 0, + Fields::Named(f) => f.named.len(), + Fields::Unnamed(f) => f.unnamed.len(), + } + } + + /// Returns `true` if there are zero fields. + pub fn is_empty(&self) -> bool { + match self { + Fields::Unit => true, + Fields::Named(f) => f.named.is_empty(), + Fields::Unnamed(f) => f.unnamed.is_empty(), + } + } + + return_impl_trait! { + /// Get an iterator over the fields of a struct or variant as [`Member`]s. + /// This iterator can be used to iterate over a named or unnamed struct or + /// variant's fields uniformly. + /// + /// # Example + /// + /// The following is a simplistic [`Clone`] derive for structs. (A more + /// complete implementation would additionally want to infer trait bounds on + /// the generic type parameters.) + /// + /// ``` + /// # use quote::quote; + /// # + /// fn derive_clone(input: &syn::ItemStruct) -> proc_macro2::TokenStream { + /// let ident = &input.ident; + /// let members = input.fields.members(); + /// let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl(); + /// quote! { + /// impl #impl_generics Clone for #ident #ty_generics #where_clause { + /// fn clone(&self) -> Self { + /// Self { + /// #(#members: self.#members.clone()),* + /// } + /// } + /// } + /// } + /// } + /// ``` + /// + /// For structs with named fields, it produces an expression like `Self { a: + /// self.a.clone() }`. For structs with unnamed fields, `Self { 0: + /// self.0.clone() }`. And for unit structs, `Self {}`. + pub fn members(&self) -> impl Iterator + Clone + '_ [Members] { + Members { + fields: self.iter(), + index: 0, + } + } + } +} + +impl IntoIterator for Fields { + type Item = Field; + type IntoIter = punctuated::IntoIter; + + fn into_iter(self) -> Self::IntoIter { + match self { + Fields::Unit => Punctuated::::new().into_iter(), + Fields::Named(f) => f.named.into_iter(), + Fields::Unnamed(f) => f.unnamed.into_iter(), + } + } +} + +impl<'a> IntoIterator for &'a Fields { + type Item = &'a Field; + type IntoIter = punctuated::Iter<'a, Field>; + + fn into_iter(self) -> Self::IntoIter { + self.iter() + } +} + +impl<'a> IntoIterator for &'a mut Fields { + type Item = &'a mut Field; + type IntoIter = punctuated::IterMut<'a, Field>; + + fn into_iter(self) -> Self::IntoIter { + self.iter_mut() + } +} + +ast_struct! { + /// A field of a struct or enum variant. + #[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))] + pub struct Field { + pub attrs: Vec, + + pub vis: Visibility, + + pub mutability: FieldMutability, + + /// Name of the field, if any. + /// + /// Fields of tuple structs have no names. + pub ident: Option, + + pub colon_token: Option, + + pub ty: Type, + } +} + +pub struct Members<'a> { + fields: punctuated::Iter<'a, Field>, + index: u32, +} + +impl<'a> Iterator for Members<'a> { + type Item = Member; + + fn next(&mut self) -> Option { + let field = self.fields.next()?; + let member = match &field.ident { + Some(ident) => Member::Named(ident.clone()), + None => { + #[cfg(all(feature = "parsing", feature = "printing"))] + let span = crate::spanned::Spanned::span(&field.ty); + #[cfg(not(all(feature = "parsing", feature = "printing")))] + let span = proc_macro2::Span::call_site(); + Member::Unnamed(Index { + index: self.index, + span, + }) + } + }; + self.index += 1; + Some(member) + } +} + +impl<'a> Clone for Members<'a> { + fn clone(&self) -> Self { + Members { + fields: self.fields.clone(), + index: self.index, + } + } +} + +#[cfg(feature = "parsing")] +pub(crate) mod parsing { + use crate::attr::Attribute; + use crate::data::{Field, Fields, FieldsNamed, FieldsUnnamed, Variant}; + use crate::error::Result; + use crate::expr::Expr; + use crate::ext::IdentExt as _; + use crate::ident::Ident; + #[cfg(not(feature = "full"))] + use crate::parse::discouraged::Speculative as _; + use crate::parse::{Parse, ParseStream}; + use crate::restriction::{FieldMutability, Visibility}; + #[cfg(not(feature = "full"))] + use crate::scan_expr::scan_expr; + use crate::token; + use crate::ty::Type; + use crate::verbatim; + + #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))] + impl Parse for Variant { + fn parse(input: ParseStream) -> Result { + let attrs = input.call(Attribute::parse_outer)?; + let _visibility: Visibility = input.parse()?; + let ident: Ident = input.parse()?; + let fields = if input.peek(token::Brace) { + Fields::Named(input.parse()?) + } else if input.peek(token::Paren) { + Fields::Unnamed(input.parse()?) + } else { + Fields::Unit + }; + let discriminant = if input.peek(Token![=]) { + let eq_token: Token![=] = input.parse()?; + #[cfg(feature = "full")] + let discriminant: Expr = input.parse()?; + #[cfg(not(feature = "full"))] + let discriminant = { + let begin = input.fork(); + let ahead = input.fork(); + let mut discriminant: Result = ahead.parse(); + if discriminant.is_ok() { + input.advance_to(&ahead); + } else if scan_expr(input).is_ok() { + discriminant = Ok(Expr::Verbatim(verbatim::between(&begin, input))); + } + discriminant? + }; + Some((eq_token, discriminant)) + } else { + None + }; + Ok(Variant { + attrs, + ident, + fields, + discriminant, + }) + } + } + + #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))] + impl Parse for FieldsNamed { + fn parse(input: ParseStream) -> Result { + let content; + Ok(FieldsNamed { + brace_token: braced!(content in input), + named: content.parse_terminated(Field::parse_named, Token![,])?, + }) + } + } + + #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))] + impl Parse for FieldsUnnamed { + fn parse(input: ParseStream) -> Result { + let content; + Ok(FieldsUnnamed { + paren_token: parenthesized!(content in input), + unnamed: content.parse_terminated(Field::parse_unnamed, Token![,])?, + }) + } + } + + impl Field { + /// Parses a named (braced struct) field. + #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))] + pub fn parse_named(input: ParseStream) -> Result { + let attrs = input.call(Attribute::parse_outer)?; + let vis: Visibility = input.parse()?; + + let unnamed_field = cfg!(feature = "full") && input.peek(Token![_]); + let ident = if unnamed_field { + input.call(Ident::parse_any) + } else { + input.parse() + }?; + + let colon_token: Token![:] = input.parse()?; + + let ty: Type = if unnamed_field + && (input.peek(Token![struct]) + || input.peek(Token![union]) && input.peek2(token::Brace)) + { + let begin = input.fork(); + input.call(Ident::parse_any)?; + input.parse::()?; + Type::Verbatim(verbatim::between(&begin, input)) + } else { + input.parse()? + }; + + Ok(Field { + attrs, + vis, + mutability: FieldMutability::None, + ident: Some(ident), + colon_token: Some(colon_token), + ty, + }) + } + + /// Parses an unnamed (tuple struct) field. + #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))] + pub fn parse_unnamed(input: ParseStream) -> Result { + Ok(Field { + attrs: input.call(Attribute::parse_outer)?, + vis: input.parse()?, + mutability: FieldMutability::None, + ident: None, + colon_token: None, + ty: input.parse()?, + }) + } + } +} + +#[cfg(feature = "printing")] +mod printing { + use crate::data::{Field, FieldsNamed, FieldsUnnamed, Variant}; + use crate::print::TokensOrDefault; + use proc_macro2::TokenStream; + use quote::{ToTokens, TokenStreamExt}; + + #[cfg_attr(docsrs, doc(cfg(feature = "printing")))] + impl ToTokens for Variant { + fn to_tokens(&self, tokens: &mut TokenStream) { + tokens.append_all(&self.attrs); + self.ident.to_tokens(tokens); + self.fields.to_tokens(tokens); + if let Some((eq_token, disc)) = &self.discriminant { + eq_token.to_tokens(tokens); + disc.to_tokens(tokens); + } + } + } + + #[cfg_attr(docsrs, doc(cfg(feature = "printing")))] + impl ToTokens for FieldsNamed { + fn to_tokens(&self, tokens: &mut TokenStream) { + self.brace_token.surround(tokens, |tokens| { + self.named.to_tokens(tokens); + }); + } + } + + #[cfg_attr(docsrs, doc(cfg(feature = "printing")))] + impl ToTokens for FieldsUnnamed { + fn to_tokens(&self, tokens: &mut TokenStream) { + self.paren_token.surround(tokens, |tokens| { + self.unnamed.to_tokens(tokens); + }); + } + } + + #[cfg_attr(docsrs, doc(cfg(feature = "printing")))] + impl ToTokens for Field { + fn to_tokens(&self, tokens: &mut TokenStream) { + tokens.append_all(&self.attrs); + self.vis.to_tokens(tokens); + if let Some(ident) = &self.ident { + ident.to_tokens(tokens); + TokensOrDefault(&self.colon_token).to_tokens(tokens); + } + self.ty.to_tokens(tokens); + } + } +} -- cgit v1.3.1