From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit `objtool` errors such as: vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a: can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd The reason is that in such builds, the Clang invocation that compiles the combined Rust plus helpers bitcode emits LLVM bitcode (again) -- the final code generation happens in the linker's LTO step, which the `-mllvm` trap options passed to Clang do not reach. This, in turn, means that unreachable traps are missing, and the impossible paths do not merely fallthrough to the next symbol, but past the end of their own section, since LTO builds place each function in its own section. Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always emits machine code directly, with the traps in place. Assisted-by: LLM Cc: Gary Guo Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- include/asm-generic/syscall.h | 164 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 164 insertions(+) create mode 100644 include/asm-generic/syscall.h (limited to 'include/asm-generic/syscall.h') diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h new file mode 100644 index 000000000..c5a3ad53b --- /dev/null +++ b/include/asm-generic/syscall.h @@ -0,0 +1,164 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Access to user system call parameters and results + * + * Copyright (C) 2008-2009 Red Hat, Inc. All rights reserved. + * + * This file is a stub providing documentation for what functions + * arch/ARCH/include/asm/syscall.h files need to define. Most arch definitions + * will be simple inlines. + * + * All of these functions expect to be called with no locks, + * and only when the caller is sure that the task of interest + * cannot return to user mode while we are looking at it. + */ + +#ifndef _ASM_SYSCALL_H +#define _ASM_SYSCALL_H 1 + +struct task_struct; +struct pt_regs; + +/** + * syscall_get_nr - find what system call a task is executing + * @task: task of interest, must be blocked + * @regs: task_pt_regs() of @task + * + * If @task is executing a system call or is at system call + * tracing about to attempt one, returns the system call number. + * If @task is not executing a system call, i.e. it's blocked + * inside the kernel for a fault or signal, returns -1. + * + * Note this returns int even on 64-bit machines. Only 32 bits of + * system call number can be meaningful. If the actual arch value + * is 64 bits, this truncates to 32 bits so 0xffffffff means -1. + * + * It's only valid to call this when @task is known to be blocked. + */ +int syscall_get_nr(struct task_struct *task, struct pt_regs *regs); + +/** + * syscall_set_nr - change the system call a task is executing + * @task: task of interest, must be blocked + * @regs: task_pt_regs() of @task + * @nr: system call number + * + * Changes the system call number @task is about to execute. + * + * It's only valid to call this when @task is stopped for tracing on + * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or + * %SYSCALL_WORK_SYSCALL_AUDIT. + */ +void syscall_set_nr(struct task_struct *task, struct pt_regs *regs, int nr); + +/** + * syscall_rollback - roll back registers after an aborted system call + * @task: task of interest, must be in system call exit tracing + * @regs: task_pt_regs() of @task + * + * It's only valid to call this when @task is stopped for system + * call exit tracing (due to %SYSCALL_WORK_SYSCALL_TRACE or + * %SYSCALL_WORK_SYSCALL_AUDIT), after ptrace_report_syscall_entry() + * returned nonzero to prevent the system call from taking place. + * + * This rolls back the register state in @regs so it's as if the + * system call instruction was a no-op. The registers containing + * the system call number and arguments are as they were before the + * system call instruction. This may not be the same as what the + * register state looked like at system call entry tracing. + */ +void syscall_rollback(struct task_struct *task, struct pt_regs *regs); + +/** + * syscall_get_error - check result of traced system call + * @task: task of interest, must be blocked + * @regs: task_pt_regs() of @task + * + * Returns 0 if the system call succeeded, or -ERRORCODE if it failed. + * + * It's only valid to call this when @task is stopped for tracing on exit + * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or + * %SYSCALL_WORK_SYSCALL_AUDIT. + */ +long syscall_get_error(struct task_struct *task, struct pt_regs *regs); + +/** + * syscall_get_return_value - get the return value of a traced system call + * @task: task of interest, must be blocked + * @regs: task_pt_regs() of @task + * + * Returns the return value of the successful system call. + * This value is meaningless if syscall_get_error() returned nonzero. + * + * It's only valid to call this when @task is stopped for tracing on exit + * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or + * %SYSCALL_WORK_SYSCALL_AUDIT. + */ +long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs); + +/** + * syscall_set_return_value - change the return value of a traced system call + * @task: task of interest, must be blocked + * @regs: task_pt_regs() of @task + * @error: negative error code, or zero to indicate success + * @val: user return value if @error is zero + * + * This changes the results of the system call that user mode will see. + * If @error is zero, the user sees a successful system call with a + * return value of @val. If @error is nonzero, it's a negated errno + * code; the user sees a failed system call with this errno code. + * + * It's only valid to call this when @task is stopped for tracing on exit + * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or + * %SYSCALL_WORK_SYSCALL_AUDIT. + */ +void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs, + int error, long val); + +/** + * syscall_get_arguments - extract system call parameter values + * @task: task of interest, must be blocked + * @regs: task_pt_regs() of @task + * @args: array filled with argument values + * + * Fetches 6 arguments to the system call. First argument is stored in +* @args[0], and so on. + * + * It's only valid to call this when @task is stopped for tracing on + * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or + * %SYSCALL_WORK_SYSCALL_AUDIT. + */ +void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs, + unsigned long *args); + +/** + * syscall_set_arguments - change system call parameter value + * @task: task of interest, must be in system call entry tracing + * @regs: task_pt_regs() of @task + * @args: array of argument values to store + * + * Changes 6 arguments to the system call. + * The first argument gets value @args[0], and so on. + * + * It's only valid to call this when @task is stopped for tracing on + * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or + * %SYSCALL_WORK_SYSCALL_AUDIT. + */ +void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs, + const unsigned long *args); + +/** + * syscall_get_arch - return the AUDIT_ARCH for the current system call + * @task: task of interest, must be blocked + * + * Returns the AUDIT_ARCH_* based on the system call convention in use. + * + * It's only valid to call this when @task is stopped on entry to a system + * call, due to %SYSCALL_WORK_SYSCALL_TRACE, %SYSCALL_WORK_SYSCALL_AUDIT, or + * %SYSCALL_WORK_SECCOMP. + * + * Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must + * provide an implementation of this. + */ +int syscall_get_arch(struct task_struct *task); +#endif /* _ASM_SYSCALL_H */ -- cgit v1.3.1