linux/tools/objtool/check.c, branch v6.15

objtool/rust: add one more `noreturn` Rust function for Rust 1.87.0

2025-05-06T22:08:51Z

Starting with Rust 1.87.0 (expected 2025-05-15), `objtool` may report: rust/core.o: warning: objtool: _R..._4core9panicking9panic_fmt() falls through to next function _R..._4core9panicking18panic_nounwind_fmt() rust/core.o: warning: objtool: _R..._4core9panicking18panic_nounwind_fmt() falls through to next function _R..._4core9panicking5panic() The reason is that `rust_begin_unwind` is now mangled: _R..._7___rustc17rust_begin_unwind Thus add the mangled one to the list so that `objtool` knows it is actually `noreturn`. See commit 56d680dd23c3 ("objtool/rust: list `noreturn` Rust functions") for more details. Alternatively, we could remove the fixed one in `noreturn.h` and relax this test to cover both, but it seems best to be strict as long as we can. Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs). Cc: Josh Poimboeuf Cc: Peter Zijlstra Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20250502140237.1659624-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda

Merge tag 'rust-fixes-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux

2025-04-19T17:02:43Z

Pull rust fixes from Miguel Ojeda: "Toolchain and infrastructure: - Fix missing KASAN LLVM flags on first build (and fix spurious rebuilds) by skipping '--target' - Fix Make < 4.3 build error by using '$(pound)' - Fix UML build error by removing 'volatile' qualifier from io helpers - Fix UML build error by adding 'dma_{alloc,free}_attrs()' helpers - Clean gendwarfksyms warnings by avoiding to export '__pfx' symbols - Clean objtool warning by adding a new 'noreturn' function for 1.86.0 - Disable 'needless_continue' Clippy lint due to new 1.86.0 warnings - Add missing 'ffi' crate to 'generate_rust_analyzer.py' 'pin-init' crate: - Import a couple fixes from upstream" * tag 'rust-fixes-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux: rust: helpers: Add dma_alloc_attrs() and dma_free_attrs() rust: helpers: Remove volatile qualifier from io helpers rust: kbuild: use `pound` to support GNU Make < 4.3 objtool/rust: add one more `noreturn` Rust function for Rust 1.86.0 rust: kasan/kbuild: fix missing flags on first build rust: disable `clippy::needless_continue` rust: kbuild: Don't export __pfx symbols rust: pin-init: use Markdown autolinks in Rust comments rust: pin-init: alloc: restrict `impl ZeroableOption` for `Box` to `T: Sized` scripts: generate_rust_analyzer: Add ffi crate

objtool/rust: add one more `noreturn` Rust function for Rust 1.86.0

2025-04-14T15:02:49Z

Starting with Rust 1.86.0 (see upstream commit b151b513ba2b ("Insert null checks for pointer dereferences when debug assertions are enabled") [1]), under some kernel configurations with `CONFIG_RUST_DEBUG_ASSERTIONS=y`, one may trigger a new `objtool` warning: rust/kernel.o: warning: objtool: _R..._6kernel9workqueue6system() falls through to next function _R...9workqueue14system_highpri() due to a call to the `noreturn` symbol: core::panicking::panic_null_pointer_dereference Thus add it to the list so that `objtool` knows it is actually `noreturn`. See commit 56d680dd23c3 ("objtool/rust: list `noreturn` Rust functions") for more details. Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs). Fixes: 56d680dd23c3 ("objtool/rust: list `noreturn` Rust functions") Link: https://github.com/rust-lang/rust/commit/b151b513ba2b65c7506ec1a80f2712bbd09154d1 [1] Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20250413002338.1741593-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda

objtool: Remove ANNOTATE_IGNORE_ALTERNATIVE from CLAC/STAC

2025-04-08T20:03:51Z

ANNOTATE_IGNORE_ALTERNATIVE adds additional noise to the code generated by CLAC/STAC alternatives, hurting readability for those whose read uaccess-related code generation on a regular basis. Remove the annotation specifically for the "NOP patched with CLAC/STAC" case in favor of a manual check. Leave the other uses of that annotation in place as they're less common and more difficult to detect. Suggested-by: Linus Torvalds Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Acked-by: Linus Torvalds Link: https://lore.kernel.org/r/fc972ba4995d826fcfb8d02733a14be8d670900b.1744098446.git.jpoimboe@kernel.org

objtool, xen: Fix INSN_SYSCALL / INSN_SYSRET semantics

2025-04-08T07:14:12Z

Objtool uses an arbitrary rule for INSN_SYSCALL and INSN_SYSRET that almost works by accident: if it's in a function, control flow continues after the instruction, otherwise it terminates. That behavior should instead be based on the semantics of the underlying instruction. Change INSN_SYSCALL to always preserve control flow and INSN_SYSRET to always terminate it. The changed semantic for INSN_SYSCALL requires a tweak to the !CONFIG_IA32_EMULATION version of xen_entry_SYSCALL_compat(). In Xen, SYSCALL is a hypercall which usually returns. But in this case it's a hypercall to IRET which doesn't return. Add UD2 to tell objtool to terminate control flow, and to prevent undefined behavior at runtime. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Reviewed-by: Juergen Gross # for the Xen part Cc: Linus Torvalds Link: https://lore.kernel.org/r/19453dfe9a0431b7f016e9dc16d031cad3812a50.1744095216.git.jpoimboe@kernel.org

objtool: Stop UNRET validation on UD2

2025-04-08T07:14:11Z

In preparation for simplifying INSN_SYSCALL, make validate_unret() terminate control flow on UD2 just like validate_branch() already does. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/ce841269e7e28c8b7f32064464a9821034d724ff.1744095216.git.jpoimboe@kernel.org

objtool: Split INSN_CONTEXT_SWITCH into INSN_SYSCALL and INSN_SYSRET

2025-04-08T07:14:11Z

INSN_CONTEXT_SWITCH is ambiguous. It can represent both call semantics (SYSCALL, SYSENTER) and return semantics (SYSRET, IRET, RETS, RETU). Those differ significantly: calls preserve control flow whereas returns terminate it. Objtool uses an arbitrary rule for INSN_CONTEXT_SWITCH that almost works by accident: if in a function, keep going; otherwise stop. It should instead be based on the semantics of the underlying instruction. In preparation for improving that, split INSN_CONTEXT_SWITCH into INSN_SYCALL and INSN_SYSRET. No functional change. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/19a76c74d2c051d3bc9a775823cafc65ad267a7a.1744095216.git.jpoimboe@kernel.org

objtool: Fix INSN_CONTEXT_SWITCH handling in validate_unret()

2025-04-08T07:14:11Z

The !CONFIG_IA32_EMULATION version of xen_entry_SYSCALL_compat() ends with a SYSCALL instruction which is classified by objtool as INSN_CONTEXT_SWITCH. Unlike validate_branch(), validate_unret() doesn't consider INSN_CONTEXT_SWITCH in a non-function to be a dead end, so it keeps going past the end of xen_entry_SYSCALL_compat(), resulting in the following warning: vmlinux.o: warning: objtool: xen_reschedule_interrupt+0x2a: RET before UNTRAIN Fix that by adding INSN_CONTEXT_SWITCH handling to validate_unret() to match what validate_branch() is already doing. Fixes: a09a6e2399ba ("objtool: Add entry UNRET validation") Reported-by: Andrew Cooper Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/f5eda46fd09f15b1f5cde3d9ae3b92b958342add.1744095216.git.jpoimboe@kernel.org

objtool: Fix verbose disassembly if CROSS_COMPILE isn't set

2025-04-01T07:07:13Z

In verbose mode, when printing the disassembly of affected functions, if CROSS_COMPILE isn't set, the objdump command string gets prefixed with "(null)". Somehow this worked before. Maybe some versions of glibc return an empty string instead of NULL. Fix it regardless. [ jpoimboe: Rewrite commit log. ] Fixes: ca653464dd097 ("objtool: Add verbose option for disassembling affected functions") Signed-off-by: David Laight Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/20250215142321.14081-1-david.laight.linux@gmail.com Link: https://lore.kernel.org/r/b931a4786bc0127aa4c94e8b35ed617dcbd3d3da.1743481539.git.jpoimboe@kernel.org

objtool: Change "warning:" to "error: " for fatal errors

2025-04-01T07:07:13Z

This is similar to GCC's behavior and makes it more obvious why the build failed. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/0ea76f4b0e7a370711ed9f75fd0792bb5979c2bf.1743481539.git.jpoimboe@kernel.org