Add missing module flags for `-Zfunction-return=thunk-extern` #130824

Darksonn · 2024-09-25T09:52:38Z

This fixes a bug in the -Zfunction-return=thunk-extern flag. The flag needs to be passed onto LLVM to ensure that functions such as asan.module_ctor and asan.module_dtor that are created internally in LLVM have the mitigation applied to them.

This was originally discovered in the Linux kernel.

Original flag PR: #116892
PR for similar issue: #129373
Tracking issue: #116853

cc @ojeda
r? @wesleywiser

Darksonn · 2024-09-25T09:52:43Z

Click to see output with and without PR

Without this PR:

aliceryhl@aliceryhl-l:~/rust-for-linux$ rustc --version --verbose
rustc 1.81.0 (eeb90cda1 2024-09-04)
binary: rustc
commit-hash: eeb90cda1969383f56a2637cbd3037bdf598841c
commit-date: 2024-09-04
host: x86_64-unknown-linux-gnu
release: 1.81.0
LLVM version: 18.1.7

aliceryhl@aliceryhl-l:~/rust-for-linux$ make LLVM=1 O=~/lout 
make[1]: Entering directory '/home/aliceryhl/lout'
  SYNC    include/config/auto.conf.cmd
  GEN     Makefile
  GEN     Makefile
  CALL    /home/aliceryhl/rust-for-linux/scripts/checksyscalls.sh
  DESCEND objtool
  INSTALL libsubcmd_headers
  RUSTC L rust/core.o
rust/core.o: warning: objtool: asan.module_ctor+0x13: 'naked' return found in MITIGATION_RETHUNK build
rust/core.o: warning: objtool: asan.module_dtor+0x13: 'naked' return found in MITIGATION_RETHUNK build
  EXPORTS rust/exports_core_generated.h
  RUSTC P rust/libmacros.so
  RUSTC L rust/compiler_builtins.o
rust/compiler_builtins.o: warning: objtool: asan.module_ctor+0x0: 'naked' return found in MITIGATION_RETHUNK build
  RUSTC L rust/alloc.o
rust/alloc.o: warning: objtool: asan.module_ctor+0x13: 'naked' return found in MITIGATION_RETHUNK build
rust/alloc.o: warning: objtool: asan.module_dtor+0x13: 'naked' return found in MITIGATION_RETHUNK build
  EXPORTS rust/exports_alloc_generated.h
  RUSTC L rust/bindings.o
rust/bindings.o: warning: objtool: asan.module_ctor+0x0: 'naked' return found in MITIGATION_RETHUNK build
  EXPORTS rust/exports_bindings_generated.h
  RUSTC L rust/build_error.o
  RUSTC L rust/uapi.o
rust/uapi.o: warning: objtool: asan.module_ctor+0x0: 'naked' return found in MITIGATION_RETHUNK build
  RUSTC L rust/kernel.o
rust/kernel.o: warning: objtool: asan.module_ctor+0x13: 'naked' return found in MITIGATION_RETHUNK build
rust/kernel.o: warning: objtool: asan.module_dtor+0x13: 'naked' return found in MITIGATION_RETHUNK build
  EXPORTS rust/exports_kernel_generated.h
  CC      rust/exports.o
  AR      rust/built-in.a
  RUSTC     samples/rust/rust_print.o
samples/rust/rust_print.o: warning: objtool: asan.module_ctor+0x13: 'naked' return found in MITIGATION_RETHUNK build
samples/rust/rust_print.o: warning: objtool: asan.module_dtor+0x13: 'naked' return found in MITIGATION_RETHUNK build
  AR      samples/rust/built-in.a
  AR      samples/built-in.a
  AR      built-in.a
  AR      vmlinux.a
  LD      vmlinux.o
  OBJCOPY modules.builtin.modinfo
  GEN     modules.builtin
  MODPOST vmlinux.symvers
  UPD     include/generated/utsversion.h
  CC      init/version-timestamp.o
  LD      vmlinux
  NM      System.map
  SORTTAB vmlinux
  VOFFSET arch/x86/boot/compressed/../voffset.h
  CC      arch/x86/boot/compressed/misc.o
  OBJCOPY arch/x86/boot/compressed/vmlinux.bin
  GZIP    arch/x86/boot/compressed/vmlinux.bin.gz
  MKPIGGY arch/x86/boot/compressed/piggy.S
  AS      arch/x86/boot/compressed/piggy.o
  LD      arch/x86/boot/compressed/vmlinux
  ZOFFSET arch/x86/boot/zoffset.h
  AS      arch/x86/boot/header.o
  CC      arch/x86/boot/version.o
  LD      arch/x86/boot/setup.elf
  OBJCOPY arch/x86/boot/setup.bin
  OBJCOPY arch/x86/boot/vmlinux.bin
  BUILD   arch/x86/boot/bzImage
Kernel: arch/x86/boot/bzImage is ready  (#5)
make[1]: Leaving directory '/home/aliceryhl/lout'

With this PR:

aliceryhl@aliceryhl-l:~/rust-for-linux$ rustc --version --verbose
rustc 1.83.0-dev
binary: rustc
commit-hash: unknown
commit-date: unknown
host: x86_64-unknown-linux-gnu
release: 1.83.0-dev
LLVM version: 19.1.0

aliceryhl@aliceryhl-l:~/rust-for-linux$ make LLVM=1 O=~/lout 
make[1]: Entering directory '/home/aliceryhl/lout'
  SYNC    include/config/auto.conf.cmd
  GEN     Makefile
  GEN     Makefile
  CALL    /home/aliceryhl/rust-for-linux/scripts/checksyscalls.sh
  DESCEND objtool
  INSTALL libsubcmd_headers
  RUSTC L rust/core.o
  EXPORTS rust/exports_core_generated.h
  RUSTC P rust/libmacros.so
  RUSTC L rust/compiler_builtins.o
  RUSTC L rust/alloc.o
  EXPORTS rust/exports_alloc_generated.h
  RUSTC L rust/bindings.o
  EXPORTS rust/exports_bindings_generated.h
  RUSTC L rust/build_error.o
  RUSTC L rust/uapi.o
  RUSTC L rust/kernel.o
  EXPORTS rust/exports_kernel_generated.h
  CC      rust/exports.o
  AR      rust/built-in.a
  RUSTC     samples/rust/rust_print.o
  AR      samples/rust/built-in.a
  AR      samples/built-in.a
  AR      built-in.a
  AR      vmlinux.a
  LD      vmlinux.o
  OBJCOPY modules.builtin.modinfo
  GEN     modules.builtin
  MODPOST vmlinux.symvers
  UPD     include/generated/utsversion.h
  CC      init/version-timestamp.o
  LD      vmlinux
  NM      System.map
  SORTTAB vmlinux
  VOFFSET arch/x86/boot/compressed/../voffset.h
  CC      arch/x86/boot/compressed/misc.o
  OBJCOPY arch/x86/boot/compressed/vmlinux.bin
  GZIP    arch/x86/boot/compressed/vmlinux.bin.gz
  MKPIGGY arch/x86/boot/compressed/piggy.S
  AS      arch/x86/boot/compressed/piggy.o
  LD      arch/x86/boot/compressed/vmlinux
  ZOFFSET arch/x86/boot/zoffset.h
  AS      arch/x86/boot/header.o
  CC      arch/x86/boot/version.o
  LD      arch/x86/boot/setup.elf
  OBJCOPY arch/x86/boot/setup.bin
  OBJCOPY arch/x86/boot/vmlinux.bin
  BUILD   arch/x86/boot/bzImage
Kernel: arch/x86/boot/bzImage is ready  (#6)
make[1]: Leaving directory '/home/aliceryhl/lout'

ojeda

Looks good to me -- thanks for fixing this!

tests/codegen/function-return.rs

compiler/rustc_codegen_llvm/src/context.rs

ojeda · 2024-09-25T10:07:33Z

@rustbot label A-rust-for-linux

When enabling both KASAN and RETHUNK, objtool emits the following warnings: rust/core.o: warning: objtool: asan.module_ctor+0x13: 'naked' return found in MITIGATION_RETHUNK build rust/core.o: warning: objtool: asan.module_dtor+0x13: 'naked' return found in MITIGATION_RETHUNK build This is caused by the -Zfunction-return=thunk-extern flag in rustc not informing LLVM about the mitigation at the module level (it does so at the function level only currently, which covers most cases, but both are required), which means that the KASAN functions asan.module_ctor and asan.module_dtor are generated without the rethunk mitigation. The other mitigations that we enabled for Rust (SLS, RETPOLINE) do not have the same bug, as they're being applied through the target-feature functionality instead. This is being fixed for rustc 1.83.0, so update Kconfig to reject this configuration on older compilers. Link: rust-lang/rust#130824 Fixes: d786855 ("x86/rust: support MITIGATION_RETHUNK") Reported-by: Miguel Ojeda <ojeda@kernel.org> Closes: https://lore.kernel.org/all/CANiq72myZL4_poCMuNFevtpYYc0V0embjSuKb7y=C+m3vVA_8g@mail.gmail.com/ Signed-off-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20240926093849.1192264-1-aliceryhl@google.com [ Reworded to add the details mentioned in the list. - Miguel ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

wesleywiser · 2024-10-07T21:05:01Z

Thanks @Darksonn and @ojeda!

@bors r+ rollup

bors · 2024-10-07T21:05:04Z

📌 Commit 540e41f has been approved by wesleywiser

It is now in the queue for this repository.

…sleywiser Add missing module flags for `-Zfunction-return=thunk-extern` This fixes a bug in the `-Zfunction-return=thunk-extern` flag. The flag needs to be passed onto LLVM to ensure that functions such as `asan.module_ctor` and `asan.module_dtor` that are created internally in LLVM have the mitigation applied to them. This was originally discovered [in the Linux kernel](https://lore.kernel.org/all/CANiq72myZL4_poCMuNFevtpYYc0V0embjSuKb7y=C+m3vVA_8g@mail.gmail.com/). Original flag PR: rust-lang#116892 PR for similar issue: rust-lang#129373 Tracking issue: rust-lang#116853 cc `@ojeda` r? `@wesleywiser`

…llaumeGomez Rollup of 4 pull requests Successful merges: - rust-lang#130824 (Add missing module flags for `-Zfunction-return=thunk-extern`) - rust-lang#131170 (Fix `target_vendor` in non-IDF Xtensa ESP32 targets) - rust-lang#131369 (Update books) - rust-lang#131370 (rustdoc: improve `<wbr>`-insertion for SCREAMING_CAMEL_CASE) r? `@ghost` `@rustbot` modify labels: rollup

Rollup of 7 pull requests Successful merges: - rust-lang#130824 (Add missing module flags for `-Zfunction-return=thunk-extern`) - rust-lang#131170 (Fix `target_vendor` in non-IDF Xtensa ESP32 targets) - rust-lang#131355 (Add tests for some old fixed issues) - rust-lang#131369 (Update books) - rust-lang#131370 (rustdoc: improve `<wbr>`-insertion for SCREAMING_CAMEL_CASE) - rust-lang#131379 (Fix utf8-bom test) - rust-lang#131385 (Un-vacation myself) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#130824 - Darksonn:fix-function-return, r=wesleywiser Add missing module flags for `-Zfunction-return=thunk-extern` This fixes a bug in the `-Zfunction-return=thunk-extern` flag. The flag needs to be passed onto LLVM to ensure that functions such as `asan.module_ctor` and `asan.module_dtor` that are created internally in LLVM have the mitigation applied to them. This was originally discovered [in the Linux kernel](https://lore.kernel.org/all/CANiq72myZL4_poCMuNFevtpYYc0V0embjSuKb7y=C+m3vVA_8g@mail.gmail.com/). Original flag PR: rust-lang#116892 PR for similar issue: rust-lang#129373 Tracking issue: rust-lang#116853 cc ``@ojeda`` r? ``@wesleywiser``

When enabling both KASAN and RETHUNK, objtool emits the following warnings: rust/core.o: warning: objtool: asan.module_ctor+0x13: 'naked' return found in MITIGATION_RETHUNK build rust/core.o: warning: objtool: asan.module_dtor+0x13: 'naked' return found in MITIGATION_RETHUNK build This is caused by the -Zfunction-return=thunk-extern flag in rustc not informing LLVM about the mitigation at the module level (it does so at the function level only currently, which covers most cases, but both are required), which means that the KASAN functions asan.module_ctor and asan.module_dtor are generated without the rethunk mitigation. The other mitigations that we enabled for Rust (SLS, RETPOLINE) do not have the same bug, as they're being applied through the target-feature functionality instead. This is being fixed for rustc 1.83.0, so update Kconfig to reject this configuration on older compilers. Link: rust-lang/rust#130824 Fixes: d786855 ("x86/rust: support MITIGATION_RETHUNK") Reported-by: Miguel Ojeda <ojeda@kernel.org> Closes: https://lore.kernel.org/all/CANiq72myZL4_poCMuNFevtpYYc0V0embjSuKb7y=C+m3vVA_8g@mail.gmail.com/ Signed-off-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20240926093849.1192264-1-aliceryhl@google.com [ Reworded to add the details mentioned in the list. - Miguel ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

rustbot assigned wesleywiser Sep 25, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 25, 2024

ojeda mentioned this pull request Sep 25, 2024

Rust unstable features needed for the kernel Rust-for-Linux/linux#2

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89 tasks

ojeda reviewed Sep 25, 2024

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rustbot added the A-rust-for-linux Relevant for the Rust-for-Linux project label Sep 25, 2024

Darksonn force-pushed the fix-function-return branch from 8f223ff to ad3cc68 Compare September 25, 2024 13:52

Add missing module flags for function-return=thunk-extern

540e41f

Darksonn force-pushed the fix-function-return branch from ad3cc68 to 540e41f Compare September 25, 2024 13:53

wesleywiser approved these changes Oct 7, 2024

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 7, 2024

GuillaumeGomez mentioned this pull request Oct 7, 2024

Rollup of 4 pull requests #131380

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Zalathar mentioned this pull request Oct 8, 2024

Rollup of 7 pull requests #131387

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bors merged commit 4d63896 into rust-lang:master Oct 8, 2024
6 checks passed

rustbot added this to the 1.83.0 milestone Oct 8, 2024

Darksonn deleted the fix-function-return branch October 8, 2024 19:08

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Add missing module flags for `-Zfunction-return=thunk-extern` #130824

Add missing module flags for `-Zfunction-return=thunk-extern` #130824

Darksonn commented Sep 25, 2024

Darksonn commented Sep 25, 2024

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wesleywiser commented Oct 7, 2024

bors commented Oct 7, 2024

Add missing module flags for -Zfunction-return=thunk-extern #130824

Add missing module flags for -Zfunction-return=thunk-extern #130824

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bors commented Oct 7, 2024

Add missing module flags for `-Zfunction-return=thunk-extern` #130824

Add missing module flags for `-Zfunction-return=thunk-extern` #130824