Auto merge of #127076 - matthiaskrgr:rollup-l01gm36, r=matthiaskrgr

Rollup of 6 pull requests

Successful merges:

 - #124741 (patchable-function-entry: Add unstable compiler flag and attribute)
 - #126470 (make cargo submodule optional)
 - #126956 (core: avoid `extern type`s in formatting infrastructure)
 - #126970 (Simplify `str::clone_into`)
 - #127022 (Support fetching `Attribute` of items.)
 - #127058 (Tighten `fn_decl_span` for async blocks)

r? `@ghost`
`@rustbot` modify labels: rollup

22 files changed, 331 insertions, 25 deletions

diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 4a3ce0e0c30..f5e79c04d78 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -1454,7 +1454,10 @@ pub enum ExprKind {
     Block(P<Block>, Option<Label>),
     /// An `async` block (`async move { ... }`),
     /// or a `gen` block (`gen move { ... }`)
-    Gen(CaptureBy, P<Block>, GenBlockKind),
+    ///
+    /// The span is the "decl", which is the header before the body `{ }`
+    /// including the `asyng`/`gen` keywords and possibly `move`.
+    Gen(CaptureBy, P<Block>, GenBlockKind, Span),
     /// An await expression (`my_future.await`). Span is of await keyword.
     Await(P<Expr>, Span),
 
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index a81c335aa23..27e781a5a63 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -1528,8 +1528,9 @@ pub fn noop_visit_expr<T: MutVisitor>(
             visit_opt(label, |label| vis.visit_label(label));
             vis.visit_block(blk);
         }
-        ExprKind::Gen(_capture_by, body, _kind) => {
+        ExprKind::Gen(_capture_by, body, _kind, decl_span) => {
             vis.visit_block(body);
+            vis.visit_span(decl_span);
         }
         ExprKind::Await(expr, await_kw_span) => {
             vis.visit_expr(expr);
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index 0f3c30048ce..26cb04d4d47 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -1122,7 +1122,7 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) -> V
             visit_opt!(visitor, visit_label, opt_label);
             try_visit!(visitor.visit_block(block));
         }
-        ExprKind::Gen(_capt, body, _kind) => try_visit!(visitor.visit_block(body)),
+        ExprKind::Gen(_capt, body, _kind, _decl_span) => try_visit!(visitor.visit_block(body)),
         ExprKind::Await(expr, _span) => try_visit!(visitor.visit_expr(expr)),
         ExprKind::Assign(lhs, rhs, _span) => {
             try_visit!(visitor.visit_expr(lhs));
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 79cff0fbcd2..624bca525b9 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -227,7 +227,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         *fn_arg_span,
                     ),
                 },
-                ExprKind::Gen(capture_clause, block, genblock_kind) => {
+                ExprKind::Gen(capture_clause, block, genblock_kind, decl_span) => {
                     let desugaring_kind = match genblock_kind {
                         GenBlockKind::Async => hir::CoroutineDesugaring::Async,
                         GenBlockKind::Gen => hir::CoroutineDesugaring::Gen,
@@ -237,6 +237,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         *capture_clause,
                         e.id,
                         None,
+                        *decl_span,
                         e.span,
                         desugaring_kind,
                         hir::CoroutineSource::Block,
@@ -616,6 +617,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         capture_clause: CaptureBy,
         closure_node_id: NodeId,
         return_ty: Option<hir::FnRetTy<'hir>>,
+        fn_decl_span: Span,
         span: Span,
         desugaring_kind: hir::CoroutineDesugaring,
         coroutine_source: hir::CoroutineSource,
@@ -692,7 +694,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             bound_generic_params: &[],
             fn_decl,
             body,
-            fn_decl_span: self.lower_span(span),
+            fn_decl_span: self.lower_span(fn_decl_span),
             fn_arg_span: None,
             kind: hir::ClosureKind::Coroutine(coroutine_kind),
             constness: hir::Constness::NotConst,
@@ -1083,6 +1085,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let (parameters, expr) = this.lower_coroutine_body_with_moved_arguments(
                     &inner_decl,
                     |this| this.with_new_scopes(fn_decl_span, |this| this.lower_expr_mut(body)),
+                    fn_decl_span,
                     body.span,
                     coroutine_kind,
                     hir::CoroutineSource::Closure,
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 4c7e8c24d32..74e04eff4f3 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -211,6 +211,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     // declaration (decl), not the return types.
                     let coroutine_kind = header.coroutine_kind;
                     let body_id = this.lower_maybe_coroutine_body(
+                        *fn_sig_span,
                         span,
                         hir_id,
                         decl,
@@ -799,6 +800,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }
             AssocItemKind::Fn(box Fn { sig, generics, body: Some(body), .. }) => {
                 let body_id = self.lower_maybe_coroutine_body(
+                    sig.span,
                     i.span,
                     hir_id,
                     &sig.decl,
@@ -915,6 +917,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             ),
             AssocItemKind::Fn(box Fn { sig, generics, body, .. }) => {
                 let body_id = self.lower_maybe_coroutine_body(
+                    sig.span,
                     i.span,
                     hir_id,
                     &sig.decl,
@@ -1111,6 +1114,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     /// `gen {}` block as appropriate.
     fn lower_maybe_coroutine_body(
         &mut self,
+        fn_decl_span: Span,
         span: Span,
         fn_id: hir::HirId,
         decl: &FnDecl,
@@ -1124,6 +1128,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             let (parameters, expr) = this.lower_coroutine_body_with_moved_arguments(
                 decl,
                 |this| this.lower_block_expr(body),
+                fn_decl_span,
                 body.span,
                 coroutine_kind,
                 hir::CoroutineSource::Fn,
@@ -1145,6 +1150,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         &mut self,
         decl: &FnDecl,
         lower_body: impl FnOnce(&mut LoweringContext<'_, 'hir>) -> hir::Expr<'hir>,
+        fn_decl_span: Span,
         body_span: Span,
         coroutine_kind: CoroutineKind,
         coroutine_source: hir::CoroutineSource,
@@ -1315,13 +1321,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
         };
         let closure_id = coroutine_kind.closure_id();
 
-        let span = if let FnRetTy::Default(span) = decl.output
-            && matches!(coroutine_source, rustc_hir::CoroutineSource::Closure)
-        {
-            body_span.with_lo(span.lo())
-        } else {
-            body_span
-        };
         let coroutine_expr = self.make_desugared_coroutine_expr(
             // The default capture mode here is by-ref. Later on during upvar analysis,
             // we will force the captured arguments to by-move, but for async closures,
@@ -1330,7 +1329,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
             CaptureBy::Ref,
             closure_id,
             None,
-            span,
+            fn_decl_span,
+            body_span,
             desugaring_kind,
             coroutine_source,
             mkbody,
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
index f2f6594e686..3d1f43a3766 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
@@ -540,7 +540,7 @@ impl<'a> State<'a> {
                 self.ibox(0);
                 self.print_block_with_attrs(blk, attrs);
             }
-            ast::ExprKind::Gen(capture_clause, blk, kind) => {
+            ast::ExprKind::Gen(capture_clause, blk, kind, _decl_span) => {
                 self.word_nbsp(kind.modifier());
                 self.print_capture_clause(*capture_clause);
                 // cbox/ibox in analogy to the `ExprKind::Block` arm above
diff --git a/compiler/rustc_builtin_macros/src/assert/context.rs b/compiler/rustc_builtin_macros/src/assert/context.rs
index a98cb6f0f76..c664891dad5 100644
--- a/compiler/rustc_builtin_macros/src/assert/context.rs
+++ b/compiler/rustc_builtin_macros/src/assert/context.rs
@@ -298,7 +298,7 @@ impl<'cx, 'a> Context<'cx, 'a> {
             // sync with the `rfc-2011-nicer-assert-messages/all-expr-kinds.rs` test.
             ExprKind::Assign(_, _, _)
             | ExprKind::AssignOp(_, _, _)
-            | ExprKind::Gen(_, _, _)
+            | ExprKind::Gen(_, _, _, _)
             | ExprKind::Await(_, _)
             | ExprKind::Block(_, _)
             | ExprKind::Break(_, _)
diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs
index 48693895da1..cd82894af18 100644
--- a/compiler/rustc_codegen_llvm/src/attributes.rs
+++ b/compiler/rustc_codegen_llvm/src/attributes.rs
@@ -2,7 +2,7 @@
 
 use rustc_codegen_ssa::traits::*;
 use rustc_hir::def_id::DefId;
-use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
+use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, PatchableFunctionEntry};
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::config::{FunctionReturn, OptLevel};
 use rustc_span::symbol::sym;
@@ -53,6 +53,34 @@ fn inline_attr<'ll>(cx: &CodegenCx<'ll, '_>, inline: InlineAttr) -> Option<&'ll
     }
 }
 
+#[inline]
+fn patchable_function_entry_attrs<'ll>(
+    cx: &CodegenCx<'ll, '_>,
+    attr: Option<PatchableFunctionEntry>,
+) -> SmallVec<[&'ll Attribute; 2]> {
+    let mut attrs = SmallVec::new();
+    let patchable_spec = attr.unwrap_or_else(|| {
+        PatchableFunctionEntry::from_config(cx.tcx.sess.opts.unstable_opts.patchable_function_entry)
+    });
+    let entry = patchable_spec.entry();
+    let prefix = patchable_spec.prefix();
+    if entry > 0 {
+        attrs.push(llvm::CreateAttrStringValue(
+            cx.llcx,
+            "patchable-function-entry",
+            &format!("{}", entry),
+        ));
+    }
+    if prefix > 0 {
+        attrs.push(llvm::CreateAttrStringValue(
+            cx.llcx,
+            "patchable-function-prefix",
+            &format!("{}", prefix),
+        ));
+    }
+    attrs
+}
+
 /// Get LLVM sanitize attributes.
 #[inline]
 pub fn sanitize_attrs<'ll>(
@@ -421,6 +449,7 @@ pub fn from_fn_attrs<'ll, 'tcx>(
         llvm::set_alignment(llfn, align);
     }
     to_add.extend(sanitize_attrs(cx, codegen_fn_attrs.no_sanitize));
+    to_add.extend(patchable_function_entry_attrs(cx, codegen_fn_attrs.patchable_function_entry));
 
     // Always annotate functions with the target-cpu they are compiled for.
     // Without this, ThinLTO won't inline Rust functions into Clang generated
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index d224695d1f2..56a893738df 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -1,11 +1,13 @@
 use rustc_ast::{ast, attr, MetaItemKind, NestedMetaItem};
 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
-use rustc_errors::{codes::*, struct_span_code_err};
+use rustc_errors::{codes::*, struct_span_code_err, DiagMessage, SubdiagMessage};
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
 use rustc_hir::{lang_items, weak_lang_items::WEAK_LANG_ITEMS, LangItem};
-use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
+use rustc_middle::middle::codegen_fn_attrs::{
+    CodegenFnAttrFlags, CodegenFnAttrs, PatchableFunctionEntry,
+};
 use rustc_middle::mir::mono::Linkage;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self as ty, TyCtxt};
@@ -447,6 +449,80 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     None
                 };
             }
+            sym::patchable_function_entry => {
+                codegen_fn_attrs.patchable_function_entry = attr.meta_item_list().and_then(|l| {
+                    let mut prefix = None;
+                    let mut entry = None;
+                    for item in l {
+                        let Some(meta_item) = item.meta_item() else {
+                            tcx.dcx().span_err(item.span(), "expected name value pair");
+                            continue;
+                        };
+
+                        let Some(name_value_lit) = meta_item.name_value_literal() else {
+                            tcx.dcx().span_err(item.span(), "expected name value pair");
+                            continue;
+                        };
+
+                        fn emit_error_with_label(
+                            tcx: TyCtxt<'_>,
+                            span: Span,
+                            error: impl Into<DiagMessage>,
+                            label: impl Into<SubdiagMessage>,
+                        ) {
+                            let mut err: rustc_errors::Diag<'_, _> =
+                                tcx.dcx().struct_span_err(span, error);
+                            err.span_label(span, label);
+                            err.emit();
+                        }
+
+                        let attrib_to_write = match meta_item.name_or_empty() {
+                            sym::prefix_nops => &mut prefix,
+                            sym::entry_nops => &mut entry,
+                            _ => {
+                                emit_error_with_label(
+                                    tcx,
+                                    item.span(),
+                                    "unexpected parameter name",
+                                    format!("expected {} or {}", sym::prefix_nops, sym::entry_nops),
+                                );
+                                continue;
+                            }
+                        };
+
+                        let rustc_ast::LitKind::Int(val, _) = name_value_lit.kind else {
+                            emit_error_with_label(
+                                tcx,
+                                name_value_lit.span,
+                                "invalid literal value",
+                                "value must be an integer between `0` and `255`",
+                            );
+                            continue;
+                        };
+
+                        let Ok(val) = val.get().try_into() else {
+                            emit_error_with_label(
+                                tcx,
+                                name_value_lit.span,
+                                "integer value out of range",
+                                "value must be between `0` and `255`",
+                            );
+                            continue;
+                        };
+
+                        *attrib_to_write = Some(val);
+                    }
+
+                    if let (None, None) = (prefix, entry) {
+                        tcx.dcx().span_err(attr.span, "must specify at least one parameter");
+                    }
+
+                    Some(PatchableFunctionEntry::from_prefix_and_entry(
+                        prefix.unwrap_or(0),
+                        entry.unwrap_or(0),
+                    ))
+                })
+            }
             _ => {}
         }
     }
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index 32a047a9363..f884f996927 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -585,6 +585,13 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         EncodeCrossCrate::No, derive_smart_pointer, experimental!(pointee)
     ),
 
+    // RFC 3543
+    // `#[patchable_function_entry(prefix_nops = m, entry_nops = n)]`
+    gated!(
+        patchable_function_entry, Normal, template!(List: "prefix_nops = m, entry_nops = n"), ErrorPreceding,
+        EncodeCrossCrate::Yes, experimental!(patchable_function_entry)
+    ),
+
     // ==========================================================================
     // Internal attributes: Stability, deprecation, and unsafe:
     // ==========================================================================
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index f4e20328814..ad6f7da8937 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -563,6 +563,8 @@ declare_features! (
     (unstable, offset_of_slice, "CURRENT_RUSTC_VERSION", Some(126151)),
     /// Allows using `#[optimize(X)]`.
     (unstable, optimize_attribute, "1.34.0", Some(54882)),
+    /// Allows specifying nop padding on functions for dynamic patching.
+    (unstable, patchable_function_entry, "CURRENT_RUSTC_VERSION", Some(123115)),
     /// Allows postfix match `expr.match { ... }`
     (unstable, postfix_match, "1.79.0", Some(121618)),
     /// Allows `use<'a, 'b, A, B>` in `impl Trait + use<...>` for precise capture of generic args.
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 6ffc518097e..02322c9b282 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -8,8 +8,8 @@ use rustc_session::config::{
     ErrorOutputType, ExternEntry, ExternLocation, Externs, FunctionReturn, InliningThreshold,
     Input, InstrumentCoverage, InstrumentXRay, LinkSelfContained, LinkerPluginLto, LocationDetail,
     LtoCli, NextSolverConfig, OomStrategy, Options, OutFileName, OutputType, OutputTypes, PAuthKey,
-    PacRet, Passes, Polonius, ProcMacroExecutionStrategy, Strip, SwitchWithOptPath,
-    SymbolManglingVersion, WasiExecModel,
+    PacRet, Passes, PatchableFunctionEntry, Polonius, ProcMacroExecutionStrategy, Strip,
+    SwitchWithOptPath, SymbolManglingVersion, WasiExecModel,
 };
 use rustc_session::lint::Level;
 use rustc_session::search_paths::SearchPath;
@@ -813,6 +813,11 @@ fn test_unstable_options_tracking_hash() {
     tracked!(packed_bundled_libs, true);
     tracked!(panic_abort_tests, true);
     tracked!(panic_in_drop, PanicStrategy::Abort);
+    tracked!(
+        patchable_function_entry,
+        PatchableFunctionEntry::from_total_and_prefix_nops(10, 5)
+            .expect("total must be greater than or equal to prefix")
+    );
     tracked!(plt, Some(true));
     tracked!(polonius, Polonius::Legacy);
     tracked!(precise_enum_drop_elaboration, false);
diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
index c8f0d0795a3..3ddf889b63a 100644
--- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
+++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
@@ -45,6 +45,32 @@ pub struct CodegenFnAttrs {
     /// The `#[repr(align(...))]` attribute. Indicates the value of which the function should be
     /// aligned to.
     pub alignment: Option<Align>,
+    /// The `#[patchable_function_entry(...)]` attribute. Indicates how many nops should be around
+    /// the function entry.
+    pub patchable_function_entry: Option<PatchableFunctionEntry>,
+}
+
+#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
+pub struct PatchableFunctionEntry {
+    /// Nops to prepend to the function
+    prefix: u8,
+    /// Nops after entry, but before body
+    entry: u8,
+}
+
+impl PatchableFunctionEntry {
+    pub fn from_config(config: rustc_session::config::PatchableFunctionEntry) -> Self {
+        Self { prefix: config.prefix(), entry: config.entry() }
+    }
+    pub fn from_prefix_and_entry(prefix: u8, entry: u8) -> Self {
+        Self { prefix, entry }
+    }
+    pub fn prefix(&self) -> u8 {
+        self.prefix
+    }
+    pub fn entry(&self) -> u8 {
+        self.entry
+    }
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
@@ -121,6 +147,7 @@ impl CodegenFnAttrs {
             no_sanitize: SanitizerSet::empty(),
             instruction_set: None,
             alignment: None,
+            patchable_function_entry: None,
         }
     }
 
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index e0c70884fee..3cdc20b6c65 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -3432,8 +3432,9 @@ impl<'a> Parser<'a> {
             }
         }
         let capture_clause = self.parse_capture_clause()?;
+        let decl_span = lo.to(self.prev_token.span);
         let (attrs, body) = self.parse_inner_attrs_and_block()?;
-        let kind = ExprKind::Gen(capture_clause, body, kind);
+        let kind = ExprKind::Gen(capture_clause, body, kind, decl_span);
         Ok(self.mk_expr_with_attrs(lo.to(self.prev_token.span), kind, attrs))
     }
 
@@ -4022,7 +4023,7 @@ impl MutVisitor for CondChecker<'_> {
             | ExprKind::Match(_, _, _)
             | ExprKind::Closure(_)
             | ExprKind::Block(_, _)
-            | ExprKind::Gen(_, _, _)
+            | ExprKind::Gen(_, _, _, _)
             | ExprKind::TryBlock(_)
             | ExprKind::Underscore
             | ExprKind::Path(_, _)
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
index 1bca5602a4e..80619c59cc3 100644
--- a/compiler/rustc_resolve/src/def_collector.rs
+++ b/compiler/rustc_resolve/src/def_collector.rs
@@ -334,7 +334,7 @@ impl<'a, 'b, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'b, 'tcx> {
                     None => closure_def,
                 }
             }
-            ExprKind::Gen(_, _, _) => {
+            ExprKind::Gen(_, _, _, _) => {
                 self.create_def(expr.id, kw::Empty, DefKind::Closure, expr.span)
             }
             ExprKind::ConstBlock(ref constant) => {
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 2d38ad37133..41c99f7edee 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -2965,8 +2965,9 @@ pub(crate) mod dep_tracking {
         CrateType, DebugInfo, DebugInfoCompression, ErrorOutputType, FunctionReturn,
         InliningThreshold, InstrumentCoverage, InstrumentXRay, LinkerPluginLto, LocationDetail,
         LtoCli, NextSolverConfig, OomStrategy, OptLevel, OutFileName, OutputType, OutputTypes,
-        Polonius, RemapPathScopeComponents, ResolveDocLinks, SourceFileHashAlgorithm,
-        SplitDwarfKind, SwitchWithOptPath, SymbolManglingVersion, WasiExecModel,
+        PatchableFunctionEntry, Polonius, RemapPathScopeComponents, ResolveDocLinks,
+        SourceFileHashAlgorithm, SplitDwarfKind, SwitchWithOptPath, SymbolManglingVersion,
+        WasiExecModel,
     };
     use crate::lint;
     use crate::utils::NativeLib;
@@ -3073,6 +3074,7 @@ pub(crate) mod dep_tracking {
         OomStrategy,
         LanguageIdentifier,
         NextSolverConfig,
+        PatchableFunctionEntry,
         Polonius,
         InliningThreshold,
         FunctionReturn,
@@ -3250,6 +3252,35 @@ impl DumpMonoStatsFormat {
     }
 }
 
+/// `-Z patchable-function-entry` representation - how many nops to put before and after function
+/// entry.
+#[derive(Clone, Copy, PartialEq, Hash, Debug, Default)]
+pub struct PatchableFunctionEntry {
+    /// Nops before the entry
+    prefix: u8,
+    /// Nops after the entry
+    entry: u8,
+}
+
+impl PatchableFunctionEntry {
+    pub fn from_total_and_prefix_nops(
+        total_nops: u8,
+        prefix_nops: u8,
+    ) -> Option<PatchableFunctionEntry> {
+        if total_nops < prefix_nops {
+            None
+        } else {
+            Some(Self { prefix: prefix_nops, entry: total_nops - prefix_nops })
+        }
+    }
+    pub fn prefix(&self) -> u8 {
+        self.prefix
+    }
+    pub fn entry(&self) -> u8 {
+        self.entry
+    }
+}
+
 /// `-Zpolonius` values, enabling the borrow checker polonius analysis, and which version: legacy,
 /// or future prototype.
 #[derive(Clone, Copy, PartialEq, Hash, Debug, Default)]
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 9a10adeb6d1..80f7ca544f3 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -379,6 +379,7 @@ mod desc {
     pub const parse_passes: &str = "a space-separated list of passes, or `all`";
     pub const parse_panic_strategy: &str = "either `unwind` or `abort`";
     pub const parse_on_broken_pipe: &str = "either `kill`, `error`, or `inherit`";
+    pub const parse_patchable_function_entry: &str = "either two comma separated integers (total_nops,prefix_nops), with prefix_nops <= total_nops, or one integer (total_nops)";
     pub const parse_opt_panic_strategy: &str = parse_panic_strategy;
     pub const parse_oom_strategy: &str = "either `panic` or `abort`";
     pub const parse_relro_level: &str = "one of: `full`, `partial`, or `off`";
@@ -734,6 +735,32 @@ mod parse {
         true
     }
 
+    pub(crate) fn parse_patchable_function_entry(
+        slot: &mut PatchableFunctionEntry,
+        v: Option<&str>,
+    ) -> bool {
+        let mut total_nops = 0;
+        let mut prefix_nops = 0;
+
+        if !parse_number(&mut total_nops, v) {
+            let parts = v.and_then(|v| v.split_once(',')).unzip();
+            if !parse_number(&mut total_nops, parts.0) {
+                return false;
+            }
+            if !parse_number(&mut prefix_nops, parts.1) {
+                return false;
+            }
+        }
+
+        if let Some(pfe) =
+            PatchableFunctionEntry::from_total_and_prefix_nops(total_nops, prefix_nops)
+        {
+            *slot = pfe;
+            return true;
+        }
+        false
+    }
+
     pub(crate) fn parse_oom_strategy(slot: &mut OomStrategy, v: Option<&str>) -> bool {
         match v {
             Some("panic") => *slot = OomStrategy::Panic,
@@ -1859,6 +1886,8 @@ options! {
         "panic strategy for panics in drops"),
     parse_only: bool = (false, parse_bool, [UNTRACKED],
         "parse only; do not compile, assemble, or link (default: no)"),
+    patchable_function_entry: PatchableFunctionEntry = (PatchableFunctionEntry::default(), parse_patchable_function_entry, [TRACKED],
+        "nop padding at function entry"),
     plt: Option<bool> = (None, parse_opt_bool, [TRACKED],
         "whether to use the PLT when calling into shared libraries;
         only has effect for PIC code on systems with ELF binaries
diff --git a/compiler/rustc_smir/Cargo.toml b/compiler/rustc_smir/Cargo.toml
index 1e0a60bc371..1230667ee91 100644
--- a/compiler/rustc_smir/Cargo.toml
+++ b/compiler/rustc_smir/Cargo.toml
@@ -6,6 +6,8 @@ edition = "2021"
 [dependencies]
 # tidy-alphabetical-start
 rustc_abi = { path = "../rustc_abi" }
+rustc_ast = { path = "../rustc_ast" }
+rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_middle = { path = "../rustc_middle" }
diff --git a/compiler/rustc_smir/src/rustc_smir/context.rs b/compiler/rustc_smir/src/rustc_smir/context.rs
index dde5e30c3d0..e23f4289e98 100644
--- a/compiler/rustc_smir/src/rustc_smir/context.rs
+++ b/compiler/rustc_smir/src/rustc_smir/context.rs
@@ -228,6 +228,46 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         }
     }
 
+    fn get_attrs_by_path(
+        &self,
+        def_id: stable_mir::DefId,
+        attr: &[stable_mir::Symbol],
+    ) -> Vec<stable_mir::crate_def::Attribute> {
+        let mut tables = self.0.borrow_mut();
+        let tcx = tables.tcx;
+        let did = tables[def_id];
+        let attr_name: Vec<_> =
+            attr.iter().map(|seg| rustc_span::symbol::Symbol::intern(&seg)).collect();
+        tcx.get_attrs_by_path(did, &attr_name)
+            .map(|attribute| {
+                let attr_str = rustc_ast_pretty::pprust::attribute_to_string(attribute);
+                let span = attribute.span;
+                stable_mir::crate_def::Attribute::new(attr_str, span.stable(&mut *tables))
+            })
+            .collect()
+    }
+
+    fn get_all_attrs(&self, def_id: stable_mir::DefId) -> Vec<stable_mir::crate_def::Attribute> {
+        let mut tables = self.0.borrow_mut();
+        let tcx = tables.tcx;
+        let did = tables[def_id];
+        let filter_fn = move |a: &&rustc_ast::ast::Attribute| {
+            matches!(a.kind, rustc_ast::ast::AttrKind::Normal(_))
+        };
+        let attrs_iter = if let Some(did) = did.as_local() {
+            tcx.hir().attrs(tcx.local_def_id_to_hir_id(did)).iter().filter(filter_fn)
+        } else {
+            tcx.item_attrs(did).iter().filter(filter_fn)
+        };
+        attrs_iter
+            .map(|attribute| {
+                let attr_str = rustc_ast_pretty::pprust::attribute_to_string(attribute);
+                let span = attribute.span;
+                stable_mir::crate_def::Attribute::new(attr_str, span.stable(&mut *tables))
+            })
+            .collect()
+    }
+
     fn span_to_string(&self, span: stable_mir::ty::Span) -> String {
         let tables = self.0.borrow();
         tables.tcx.sess.source_map().span_to_diagnostic_string(tables[span])
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 6d4a8c29bc9..3b6147c4c0f 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -768,6 +768,7 @@ symbols! {
         enable,
         encode,
         end,
+        entry_nops,
         enumerate_method,
         env,
         env_CFG_RELEASE: env!("CFG_RELEASE"),
@@ -1383,6 +1384,7 @@ symbols! {
         passes,
         pat,
         pat_param,
+        patchable_function_entry,
         path,
         pattern_complexity,
         pattern_parentheses,
@@ -1421,6 +1423,7 @@ symbols! {
         prefetch_read_instruction,
         prefetch_write_data,
         prefetch_write_instruction,
+        prefix_nops,
         preg,
         prelude,
         prelude_import,
diff --git a/compiler/stable_mir/src/compiler_interface.rs b/compiler/stable_mir/src/compiler_interface.rs
index 44dbf549c1a..5f2d9b96c73 100644
--- a/compiler/stable_mir/src/compiler_interface.rs
+++ b/compiler/stable_mir/src/compiler_interface.rs
@@ -6,6 +6,7 @@
 use std::cell::Cell;
 
 use crate::abi::{FnAbi, Layout, LayoutShape};
+use crate::crate_def::Attribute;
 use crate::mir::alloc::{AllocId, GlobalAlloc};
 use crate::mir::mono::{Instance, InstanceDef, StaticDef};
 use crate::mir::{BinOp, Body, Place, UnOp};
@@ -55,6 +56,15 @@ pub trait Context {
     /// Returns the name of given `DefId`
     fn def_name(&self, def_id: DefId, trimmed: bool) -> Symbol;
 
+    /// Return attributes with the given attribute name.
+    ///
+    /// Single segmented name like `#[inline]` is specified as `&["inline".to_string()]`.
+    /// Multi-segmented name like `#[rustfmt::skip]` is specified as `&["rustfmt".to_string(), "skip".to_string()]`.
+    fn get_attrs_by_path(&self, def_id: DefId, attr: &[Symbol]) -> Vec<Attribute>;
+
+    /// Get all attributes of a definition.
+    fn get_all_attrs(&self, def_id: DefId) -> Vec<Attribute>;
+
     /// Returns printable, human readable form of `Span`
     fn span_to_string(&self, span: Span) -> String;
 
diff --git a/compiler/stable_mir/src/crate_def.rs b/compiler/stable_mir/src/crate_def.rs
index 67752a5e629..d9b987c28a2 100644
--- a/compiler/stable_mir/src/crate_def.rs
+++ b/compiler/stable_mir/src/crate_def.rs
@@ -50,6 +50,21 @@ pub trait CrateDef {
         let def_id = self.def_id();
         with(|cx| cx.span_of_an_item(def_id))
     }
+
+    /// Return attributes with the given attribute name.
+    ///
+    /// Single segmented name like `#[inline]` is specified as `&["inline".to_string()]`.
+    /// Multi-segmented name like `#[rustfmt::skip]` is specified as `&["rustfmt".to_string(), "skip".to_string()]`.
+    fn attrs_by_path(&self, attr: &[Symbol]) -> Vec<Attribute> {
+        let def_id = self.def_id();
+        with(|cx| cx.get_attrs_by_path(def_id, attr))
+    }
+
+    /// Return all attributes of this definition.
+    fn all_attrs(&self) -> Vec<Attribute> {
+        let def_id = self.def_id();
+        with(|cx| cx.get_all_attrs(def_id))
+    }
 }
 
 /// A trait that can be used to retrieve a definition's type.
@@ -69,6 +84,28 @@ pub trait CrateDefType: CrateDef {
     }
 }
 
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Attribute {
+    value: String,
+    span: Span,
+}
+
+impl Attribute {
+    pub fn new(value: String, span: Span) -> Attribute {
+        Attribute { value, span }
+    }
+
+    /// Get the span of this attribute.
+    pub fn span(&self) -> Span {
+        self.span
+    }
+
+    /// Get the string representation of this attribute.
+    pub fn as_str(&self) -> &str {
+        &self.value
+    }
+}
+
 macro_rules! crate_def {
     ( $(#[$attr:meta])*
       $vis:vis $name:ident $(;)?