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[158.174.102.211]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5aed13bfd1fsm2961021e87.55.2026.07.06.10.00.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Jul 2026 10:00:31 -0700 (PDT) From: Magnus Lindholm To: richard.henderson@linaro.org, mattst88@gmail.com, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org Cc: glaubitz@physik.fu-berlin.de, mcree@orcon.net.nz, ink@unseen.parts, macro@orcam.me.uk, Magnus Lindholm Subject: [PATCH v4 2/7] alpha: add ARCH_STACKWALK-based stacktrace support Date: Mon, 6 Jul 2026 18:56:43 +0200 Message-ID: <20260706170019.2941459-3-linmag7@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260706170019.2941459-1-linmag7@gmail.com> References: <20260706170019.2941459-1-linmag7@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Implement arch_stack_walk() for Alpha using a simple kernel stack scanning walker. Start from regs+1 for current tasks to skip pt_regs and use pcb.ksp for blocked tasks. Filter candidates with __kernel_text_address() and stop at stack bounds via kstack_end(). Enable CONFIG_STACKTRACE_SUPPORT and CONFIG_ARCH_STACKWALK so generic stacktrace users (dump_stack(), /proc/*/stack, SysRq backtraces, etc.) work on Alpha. This provides functional in-kernel stack traces without requiring frame pointer unwinding. Reviewed-by: Matt Turner Tested-by: Matt Turner Signed-off-by: Magnus Lindholm --- arch/alpha/Kconfig | 4 +++ arch/alpha/kernel/Makefile | 3 +- arch/alpha/kernel/stacktrace.c | 61 +++++++++++++++++++++++++++++++++ arch/alpha/kernel/vmlinux.lds.S | 2 ++ 4 files changed, 69 insertions(+), 1 deletion(-) create mode 100644 arch/alpha/kernel/stacktrace.c diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig index f3b882835617..7ac435c56845 100644 --- a/arch/alpha/Kconfig +++ b/arch/alpha/Kconfig @@ -39,6 +39,7 @@ config ALPHA select MODULES_USE_ELF_RELA select ODD_RT_SIGACTION select OLD_SIGSUSPEND + select ARCH_STACKWALK select CPU_NO_EFFICIENT_FFS if !ALPHA_EV67 select MMU_GATHER_NO_RANGE select MMU_GATHER_RCU_TABLE_FREE @@ -80,6 +81,9 @@ config PGTABLE_LEVELS config AUDIT_ARCH bool +config STACKTRACE_SUPPORT + def_bool y + menu "System setup" choice diff --git a/arch/alpha/kernel/Makefile b/arch/alpha/kernel/Makefile index 187cd8df2faf..4ea5c189e60e 100644 --- a/arch/alpha/kernel/Makefile +++ b/arch/alpha/kernel/Makefile @@ -9,7 +9,8 @@ ccflags-y := -Wno-sign-compare obj-y := head.o entry.o traps.o process.o osf_sys.o irq.o \ irq_alpha.o signal.o setup.o ptrace.o time.o \ - systbls.o err_common.o io.o bugs.o termios.o + systbls.o err_common.o io.o bugs.o termios.o \ + stacktrace.o obj-$(CONFIG_VGA_HOSE) += console.o obj-$(CONFIG_SMP) += smp.o diff --git a/arch/alpha/kernel/stacktrace.c b/arch/alpha/kernel/stacktrace.c new file mode 100644 index 000000000000..74d95f591039 --- /dev/null +++ b/arch/alpha/kernel/stacktrace.c @@ -0,0 +1,61 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include + +#include +#include + +static __always_inline unsigned long alpha_get_current_ksp(void) +{ + unsigned long sp; + + asm volatile("mov $30, %0" : "=r"(sp)); + return sp; +} + +static void alpha_scan_kernel_stack(unsigned long ksp, + stack_trace_consume_fn consume_entry, + void *cookie) +{ + unsigned long *p = (unsigned long *)ksp; + + if (unlikely(ksp & (sizeof(unsigned long) - 1))) + return; + + while (!kstack_end(p)) { + unsigned long addr = READ_ONCE_NOCHECK(*p++); + + if (!__kernel_text_address(addr)) + continue; + + if (!consume_entry(cookie, addr)) + break; + } +} + +noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, + void *cookie, + struct task_struct *task, + struct pt_regs *regs) +{ + unsigned long ksp; + + if (!task) + task = current; + + if (regs && task == current) { + /* + * pt_regs is stored on the kernel stack; regs+1 matches + * what arch/alpha/kernel/traps.c uses as the trace start. + */ + ksp = (unsigned long)(regs + 1); + } else if (task == current) { + ksp = alpha_get_current_ksp(); + } else { + ksp = task_thread_info(task)->pcb.ksp; + } + + alpha_scan_kernel_stack(ksp, consume_entry, cookie); +} diff --git a/arch/alpha/kernel/vmlinux.lds.S b/arch/alpha/kernel/vmlinux.lds.S index 2d136c63db16..95704e64b6a6 100644 --- a/arch/alpha/kernel/vmlinux.lds.S +++ b/arch/alpha/kernel/vmlinux.lds.S @@ -28,6 +28,8 @@ SECTIONS TEXT_TEXT SCHED_TEXT LOCK_TEXT + IRQENTRY_TEXT + SOFTIRQENTRY_TEXT *(.fixup) *(.gnu.warning) } :text -- 2.53.0