kbuild: use the upstream `alloc` crate

Switch away from our fork of the `alloc` crate. We remove it altogether
in the next commit.

Signed-off-by: Wedson Almeida Filho <walmeida@microsoft.com>
Link: https://lore.kernel.org/r/20240328013603.206764-4-wedsonaf@gmail.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

rust/Makefile

@@ -61,15 +61,9 @@ core-cfgs = \
     --cfg no_fp_fmt_parse
 
 alloc-cfgs = \
-    --cfg no_borrow \
-    --cfg no_fmt \
     --cfg no_global_oom_handling \
-    --cfg no_macros \
     --cfg no_rc \
-    --cfg no_str \
-    --cfg no_string \
-    --cfg no_sync \
-    --cfg no_thin
+    --cfg no_sync
 
 quiet_cmd_rustdoc = RUSTDOC $(if $(rustdoc_host),H, ) $<
       cmd_rustdoc = \
@@ -123,7 +117,7 @@ rustdoc-compiler_builtins: $(src)/compiler_builtins.rs rustdoc-core FORCE
 # due to things that are "configured out" vs. entirely non-existing ones.
 rustdoc-alloc: private rustc_target_flags = $(alloc-cfgs) \
     -Arustdoc::broken_intra_doc_links
-rustdoc-alloc: $(src)/alloc/lib.rs rustdoc-core rustdoc-compiler_builtins FORCE
+rustdoc-alloc: $(RUST_LIB_SRC)/alloc/src/lib.rs rustdoc-core rustdoc-compiler_builtins FORCE
 	+$(call if_changed,rustdoc)
 
 rustdoc-kernel: private rustc_target_flags = --extern alloc \
@@ -219,8 +213,6 @@ rusttest: rusttest-macros rusttest-kernel
 #   - `cargo` only considers the use case of building the standard library
 #     to use it in a given package. Thus we need to create a dummy package
 #     and pick the generated libraries from there.
-#   - Since we only keep a subset of upstream `alloc` in-tree, we need
-#     to recreate it on the fly by putting our sources on top.
 #   - The usual ways of modifying the dependency graph in `cargo` do not seem
 #     to apply for the `-Zbuild-std` steps, thus we have to mislead it
 #     by modifying the sources in the sysroot.
@@ -239,8 +231,6 @@ quiet_cmd_rustsysroot = RUSTSYSROOT
 	rm -rf $(objtree)/$(obj)/test; \
 	mkdir -p $(objtree)/$(obj)/test; \
 	cp -a $(rustc_sysroot) $(objtree)/$(obj)/test/sysroot; \
-	cp -r $(srctree)/$(src)/alloc/* \
-		$(objtree)/$(obj)/test/sysroot/lib/rustlib/src/rust/library/alloc/src; \
 	echo '\#!/bin/sh' > $(objtree)/$(obj)/test/rustc_sysroot; \
 	echo "$(RUSTC) --sysroot=$(abspath $(objtree)/$(obj)/test/sysroot) \"\$$@\"" \
 		>> $(objtree)/$(obj)/test/rustc_sysroot; \
@@ -448,7 +438,7 @@ $(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
 $(obj)/alloc.o: private skip_clippy = 1
 $(obj)/alloc.o: private skip_flags = -Dunreachable_pub
 $(obj)/alloc.o: private rustc_target_flags = $(alloc-cfgs)
-$(obj)/alloc.o: $(src)/alloc/lib.rs $(obj)/compiler_builtins.o FORCE
+$(obj)/alloc.o: $(RUST_LIB_SRC)/alloc/src/lib.rs $(obj)/compiler_builtins.o FORCE
 	+$(call if_changed_dep,rustc_library)
 
 $(obj)/build_error.o: $(src)/build_error.rs $(obj)/compiler_builtins.o FORCE

rust/kernel/str.rs

@@ -2,6 +2,7 @@
 
 //! String representations.
 
+use crate::alloc::vec_ext::VecExt;
 use alloc::alloc::AllocError;
 use alloc::vec::Vec;
 use core::fmt::{self, Write};

scripts/generate_rust_analyzer.py

@@ -66,7 +66,7 @@ def generate_crates(srctree, objtree, sysroot_src, external_src, cfgs):
 
     append_crate(
         "alloc",
-        srctree / "rust" / "alloc" / "lib.rs",
+        sysroot_src / "alloc" / "src" / "lib.rs",
         ["core", "compiler_builtins"],
         cfg=crates_cfgs.get("alloc", []),
     )