From: Philippe Gerum <rpm@xenomai.org>
To: Tobias Schaffner <tobias.schaffner@siemens.com>
Cc: xenomai@lists.linux.dev
Subject: Re: [PATCH dovetail v4 11/12] riscv: add out-of-band aware trap handling
Date: Thu, 22 Jan 2026 20:57:09 +0100 [thread overview]
Message-ID: <874iodifoq.fsf@xenomai.org> (raw)
In-Reply-To: <20260122102304.421957-12-tobias.schaffner@siemens.com> (Tobias Schaffner's message of "Thu, 22 Jan 2026 11:23:03 +0100")
"riscv: dovetail: add core support" as well.
Tobias Schaffner <tobias.schaffner@siemens.com> writes:
> Introduce trap handling hooks for the Dovetail co-kernel, integrating
> out-of-band (OOB) notification and unwind support.
>
> Signed-off-by: Tobias Schaffner <tobias.schaffner@siemens.com>
> ---
> arch/riscv/kernel/traps.c | 110 ++++++++++++++++++++++++++++++++------
> arch/riscv/mm/fault.c | 21 +++++---
> 2 files changed, 108 insertions(+), 23 deletions(-)
>
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index d0400086a075..51e1407ee066 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -3,6 +3,8 @@
> * Copyright (C) 2012 Regents of the University of California
> */
>
> +#include <asm-generic/signal.h>
> +#include <linux/compiler_attributes.h>
> #include <linux/cpu.h>
> #include <linux/kernel.h>
> #include <linux/init.h>
> @@ -115,6 +117,8 @@ void die(struct pt_regs *regs, const char *str)
> static __always_inline
> bool mark_trap_entry(int signo, struct pt_regs *regs)
> {
> + oob_trap_notify(signo, regs);
> +
> /*
> * Dovetail: irqentry_enter*() already synchronized the
> * virtual and real interrupt states for us. If running
> @@ -126,21 +130,40 @@ bool mark_trap_entry(int signo, struct pt_regs *regs)
> return true;
> }
>
> + oob_trap_unwind(signo, regs);
> +
> return false;
> }
>
> static __always_inline
> void mark_trap_exit(int signo, struct pt_regs *regs)
> {
> + oob_trap_unwind(signo, regs);
> hard_cond_local_irq_disable();
> }
>
> -void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr)
> +static __always_inline
> +bool mark_trap_entry_raw(int trapnr, struct pt_regs *regs)
> {
> - struct task_struct *tsk = current;
> + oob_trap_notify(trapnr, regs);
>
> - if (!mark_trap_entry(signo, regs))
> - return;
> + if (running_oob()) {
> + oob_trap_unwind(trapnr, regs);
> + return false;
> + }
> +
> + return true;
> +}
> +
> +static __always_inline
> +void mark_trap_exit_raw(int trapnr, struct pt_regs *regs)
> +{
> + oob_trap_unwind(trapnr, regs);
> +}
> +
> +static void do_trap_raw(struct pt_regs *regs, int signo, int code, unsigned long addr)
> +{
> + struct task_struct *tsk = current;
>
> if (show_unhandled_signals && unhandled_signal(tsk, signo)
> && printk_ratelimit()) {
> @@ -153,6 +176,14 @@ void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr)
> }
>
> force_sig_fault(signo, code, (void __user *)addr);
> +}
> +
> +void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr)
> +{
> + if(!mark_trap_entry(signo, regs))
> + return;
> +
> + do_trap_raw(regs, signo, code, addr);
>
> mark_trap_exit(signo, regs);
> }
> @@ -163,7 +194,7 @@ static void do_trap_error(struct pt_regs *regs, int signo, int code,
> current->thread.bad_cause = regs->cause;
>
> if (user_mode(regs)) {
> - do_trap(regs, signo, code, addr);
> + do_trap_raw(regs, signo, code, addr);
> } else {
> /*
> * Dovetail: If we trapped from kernel space, either
> @@ -181,9 +212,12 @@ static void do_trap_error(struct pt_regs *regs, int signo, int code,
> #else
> #define __trap_section noinstr
> #endif
> -#define DO_ERROR_INFO(name, signo, code, str) \
> +#define DO_ERROR_INFO(name, signo, code, str, trapnr) \
> asmlinkage __visible __trap_section void name(struct pt_regs *regs) \
> { \
> + if(!mark_trap_entry(trapnr, regs)) \
> + return; \
> + \
> if (user_mode(regs)) { \
> irqentry_enter_from_user_mode(regs); \
> local_irq_enable(); \
> @@ -195,19 +229,24 @@ asmlinkage __visible __trap_section void name(struct pt_regs *regs) \
> do_trap_error(regs, signo, code, regs->epc, "Oops - " str); \
> irqentry_nmi_exit(regs, state); \
> } \
> + \
> + mark_trap_exit(trapnr, regs); \
> }
>
> DO_ERROR_INFO(do_trap_unknown,
> - SIGILL, ILL_ILLTRP, "unknown exception");
> + SIGILL, ILL_ILLTRP, "unknown exception", EXC_INST_ILLEGAL);
> DO_ERROR_INFO(do_trap_insn_misaligned,
> - SIGBUS, BUS_ADRALN, "instruction address misaligned");
> + SIGBUS, BUS_ADRALN, "instruction address misaligned", EXC_INST_MISALIGNED);
> DO_ERROR_INFO(do_trap_insn_fault,
> - SIGSEGV, SEGV_ACCERR, "instruction access fault");
> + SIGSEGV, SEGV_ACCERR, "instruction access fault", EXC_INST_ACCESS);
>
> asmlinkage __visible __trap_section void do_trap_insn_illegal(struct pt_regs *regs)
> {
> bool handled;
>
> + if(!mark_trap_entry(EXC_INST_ILLEGAL, regs))
> + return;
> +
> if (user_mode(regs)) {
> irqentry_enter_from_user_mode(regs);
>
> @@ -237,10 +276,11 @@ asmlinkage __visible __trap_section void do_trap_insn_illegal(struct pt_regs *re
>
> irqentry_nmi_exit(regs, state);
> }
> + mark_trap_exit(EXC_INST_ILLEGAL, regs);
> }
>
> DO_ERROR_INFO(do_trap_load_fault,
> - SIGSEGV, SEGV_ACCERR, "load access fault");
> + SIGSEGV, SEGV_ACCERR, "load access fault", EXC_LOAD_ACCESS);
>
> enum misaligned_access_type {
> MISALIGNED_STORE,
> @@ -264,6 +304,9 @@ static void do_trap_misaligned(struct pt_regs *regs, enum misaligned_access_type
> {
> irqentry_state_t state;
>
> + if(!mark_trap_entry(EXC_LOAD_MISALIGNED, regs))
> + return;
> +
> if (user_mode(regs)) {
> irqentry_enter_from_user_mode(regs);
> local_irq_enable();
> @@ -281,6 +324,8 @@ static void do_trap_misaligned(struct pt_regs *regs, enum misaligned_access_type
> } else {
> irqentry_nmi_exit(regs, state);
> }
> +
> + mark_trap_exit(EXC_LOAD_MISALIGNED, regs);
> }
>
> asmlinkage __visible __trap_section void do_trap_load_misaligned(struct pt_regs *regs)
> @@ -290,15 +335,36 @@ asmlinkage __visible __trap_section void do_trap_load_misaligned(struct pt_regs
>
> asmlinkage __visible __trap_section void do_trap_store_misaligned(struct pt_regs *regs)
> {
> - do_trap_misaligned(regs, MISALIGNED_STORE);
> + if(!mark_trap_entry(EXC_STORE_MISALIGNED, regs))
> + return;
> +
> + if (user_mode(regs)) {
> + irqentry_enter_from_user_mode(regs);
> +
> + if (handle_misaligned_store(regs))
> + do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
> + "Oops - store (or AMO) address misaligned");
> +
> + irqentry_exit_to_user_mode(regs);
> + } else {
> + irqentry_state_t state = irqentry_nmi_enter(regs);
> +
> + if (handle_misaligned_store(regs))
> + do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
> + "Oops - store (or AMO) address misaligned");
> +
> + irqentry_nmi_exit(regs, state);
> + }
> +
> + mark_trap_exit(EXC_STORE_MISALIGNED, regs);
> }
>
> DO_ERROR_INFO(do_trap_store_fault,
> - SIGSEGV, SEGV_ACCERR, "store (or AMO) access fault");
> + SIGSEGV, SEGV_ACCERR, "store (or AMO) access fault", EXC_STORE_ACCESS);
> DO_ERROR_INFO(do_trap_ecall_s,
> - SIGILL, ILL_ILLTRP, "environment call from S-mode");
> + SIGILL, ILL_ILLTRP, "environment call from S-mode", EXC_SYSCALL);
> DO_ERROR_INFO(do_trap_ecall_m,
> - SIGILL, ILL_ILLTRP, "environment call from M-mode");
> + SIGILL, ILL_ILLTRP, "environment call from M-mode", EXC_SUPERVISOR_SYSCALL);
>
> static inline unsigned long get_break_insn_length(unsigned long pc)
> {
> @@ -350,6 +416,9 @@ void handle_break(struct pt_regs *regs)
>
> asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs)
> {
> + if(!mark_trap_entry_raw(EXC_BREAKPOINT, regs))
> + return;
> +
> if (user_mode(regs)) {
> irqentry_enter_from_user_mode(regs);
> local_irq_enable();
> @@ -365,6 +434,8 @@ asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs)
>
> irqentry_nmi_exit(regs, state);
> }
> +
> + mark_trap_exit_raw(EXC_BREAKPOINT, regs);
> }
>
> asmlinkage __visible __trap_section __no_stack_protector
> @@ -381,6 +452,15 @@ void do_trap_ecall_u(struct pt_regs *regs)
>
> syscall = syscall_enter_from_user_mode(regs, syscall);
>
> + if(dovetailing()) {
> + if (syscall == EXIT_SYSCALL_OOB) {
> + hard_local_irq_disable();
> + return;
> + }
> + if (syscall == EXIT_SYSCALL_TAIL)
> + goto done_inband;
> + }
> +
> add_random_kstack_offset();
>
> if (syscall >= 0 && syscall < NR_syscalls)
> @@ -398,6 +478,7 @@ void do_trap_ecall_u(struct pt_regs *regs)
> */
> choose_random_kstack_offset(get_random_u16());
>
> +done_inband:
> syscall_exit_to_user_mode(regs);
> } else {
> irqentry_state_t state = irqentry_nmi_enter(regs);
> @@ -407,7 +488,6 @@ void do_trap_ecall_u(struct pt_regs *regs)
>
> irqentry_nmi_exit(regs, state);
> }
> -
> }
>
> #ifdef CONFIG_MMU
> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> index d64d01874a79..42450c47ee12 100644
> --- a/arch/riscv/mm/fault.c
> +++ b/arch/riscv/mm/fault.c
> @@ -385,6 +385,10 @@ void handle_page_fault(struct pt_regs *regs)
> die_kernel_fault("access to user memory without uaccess routines", addr, regs);
> }
>
> + oob_trap_notify(EXC_INST_PAGE_FAULT, regs);
> + if (!running_inband())
> + goto out;
> +
> perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
>
> if (cause == EXC_STORE_PAGE_FAULT)
> @@ -403,7 +407,7 @@ void handle_page_fault(struct pt_regs *regs)
> count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
> tsk->thread.bad_cause = cause;
> bad_area_nosemaphore(regs, SEGV_ACCERR, addr);
> - return;
> + goto out;
> }
>
> fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
> @@ -421,7 +425,7 @@ void handle_page_fault(struct pt_regs *regs)
> if (fault_signal_pending(fault, regs)) {
> if (!user_mode(regs))
> no_context(regs, addr);
> - return;
> + goto out;
> }
> lock_mmap:
>
> @@ -430,7 +434,7 @@ void handle_page_fault(struct pt_regs *regs)
> if (unlikely(!vma)) {
> tsk->thread.bad_cause = cause;
> bad_area_nosemaphore(regs, code, addr);
> - return;
> + goto out;
> }
>
> /*
> @@ -442,7 +446,7 @@ void handle_page_fault(struct pt_regs *regs)
> if (unlikely(access_error(cause, vma))) {
> tsk->thread.bad_cause = cause;
> bad_area(regs, mm, code, addr);
> - return;
> + goto out;
> }
>
> /*
> @@ -460,12 +464,12 @@ void handle_page_fault(struct pt_regs *regs)
> if (fault_signal_pending(fault, regs)) {
> if (!user_mode(regs))
> no_context(regs, addr);
> - return;
> + goto out;
> }
>
> /* The fault is fully completed (including releasing mmap lock) */
> if (fault & VM_FAULT_COMPLETED)
> - return;
> + goto out;
>
> if (unlikely(fault & VM_FAULT_RETRY)) {
> flags |= FAULT_FLAG_TRIED;
> @@ -484,7 +488,8 @@ void handle_page_fault(struct pt_regs *regs)
> if (unlikely(fault & VM_FAULT_ERROR)) {
> tsk->thread.bad_cause = cause;
> mm_fault_error(regs, addr, fault);
> - return;
> }
> - return;
> +
> +out:
> + oob_trap_unwind(EXC_INST_PAGE_FAULT, regs);
> }
--
Philippe.
next prev parent reply other threads:[~2026-01-22 19:57 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-22 10:22 [PATCH dovetail v4 00/12] riscv: Add dovetail support Tobias Schaffner
2026-01-22 10:22 ` [PATCH dovetail v4 01/12] riscv: irq_pipeline: add IRQ pipelining core Tobias Schaffner
2026-01-22 19:35 ` Philippe Gerum
2026-01-22 10:22 ` [PATCH dovetail v4 02/12] riscv: irq_pipeline: fix irq stack handling Tobias Schaffner
2026-01-22 19:55 ` Philippe Gerum
2026-01-22 10:22 ` [PATCH dovetail v4 03/12] riscv: irq_pipeline: synchronize IRQs on exit to user mode Tobias Schaffner
2026-01-22 10:22 ` [PATCH dovetail v4 04/12] irqchip/riscv-aplic-direct: enable pipelined interrupt control Tobias Schaffner
2026-01-22 10:22 ` [PATCH dovetail v4 05/12] irqchip/irq-riscv-aplic-msi: " Tobias Schaffner
2026-01-22 10:22 ` [PATCH dovetail v4 06/12] irqchip/irq-riscv-imsic-platform: " Tobias Schaffner
2026-01-22 10:22 ` [PATCH dovetail v4 07/12] irqchip/irq-riscv-intc: " Tobias Schaffner
2026-01-22 10:23 ` [PATCH dovetail v4 08/12] irqchip/irq-sifive-plic: " Tobias Schaffner
2026-01-22 10:23 ` [PATCH dovetail v4 09/12] clocksource/timer-riscv: irq_pipeline: enable pipelined clock events Tobias Schaffner
2026-01-22 10:23 ` [PATCH dovetail v4 10/12] riscv: add initial dovetail co-kernel skeleton Tobias Schaffner
2026-01-22 19:56 ` Philippe Gerum
2026-01-22 10:23 ` [PATCH dovetail v4 11/12] riscv: add out-of-band aware trap handling Tobias Schaffner
2026-01-22 19:57 ` Philippe Gerum [this message]
2026-01-22 10:23 ` [PATCH dovetail v4 12/12] riscv: add dovetail-aware memory management Tobias Schaffner
2026-01-22 11:05 ` [PATCH dovetail v4 00/12] riscv: Add dovetail support Florian Bezdeka
2026-01-22 11:48 ` Tobias Schaffner
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