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Message-ID: <CAAhV-H4qWTbjb45VNbA0is_2w1sgSW54kSngVhVpac5VehwoEg@mail.gmail.com>
Date: Tue, 2 Aug 2022 14:03:28 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Qing Zhang <zhangqing@...ngson.cn>
Cc: WANG Xuerui <kernel@...0n.name>, loongarch@...ts.linux.dev,
LKML <linux-kernel@...r.kernel.org>,
linux-arch <linux-arch@...r.kernel.org>,
Jiaxun Yang <jiaxun.yang@...goat.com>,
Arnd Bergmann <arnd@...db.de>,
Jinyang He <hejinyang@...ngson.cn>,
Youling Tang <tangyouling@...ngson.cn>
Subject: Re: [PATCH v3 3/4] LoongArch: Add stacktrace support
Hi, Qing,
Though we had an offline discussion, I still think adding get_wchan()
support is worthy. :)
Huacai
On Tue, Aug 2, 2022 at 1:38 PM Qing Zhang <zhangqing@...ngson.cn> wrote:
>
> Use common arch_stack_walk infrastructure to avoid duplicated code and
> avoid taking care of the stack storage and filtering.
> Add sra (means __schedule return address) and scfa (means __schedule call
> frame address) to thread_info and store it in switch_to().
>
> Now we can print the process stack by cat /proc/*/stack and can better
> support ftrace.
>
> Signed-off-by: Qing Zhang <zhangqing@...ngson.cn>
> ---
> arch/loongarch/Kconfig | 5 ++++
> arch/loongarch/include/asm/processor.h | 9 +++++++
> arch/loongarch/include/asm/switch_to.h | 14 ++++++----
> arch/loongarch/kernel/Makefile | 1 +
> arch/loongarch/kernel/asm-offsets.c | 2 ++
> arch/loongarch/kernel/process.c | 3 +++
> arch/loongarch/kernel/stacktrace.c | 37 ++++++++++++++++++++++++++
> arch/loongarch/kernel/switch.S | 2 ++
> 8 files changed, 68 insertions(+), 5 deletions(-)
> create mode 100644 arch/loongarch/kernel/stacktrace.c
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 62b5b07fa4e1..85d0fa3147cd 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -38,6 +38,7 @@ config LOONGARCH
> select ARCH_INLINE_SPIN_UNLOCK_IRQRESTORE if !PREEMPTION
> select ARCH_MIGHT_HAVE_PC_PARPORT
> select ARCH_MIGHT_HAVE_PC_SERIO
> + select ARCH_STACKWALK
> select ARCH_SPARSEMEM_ENABLE
> select ARCH_SUPPORTS_ACPI
> select ARCH_SUPPORTS_ATOMIC_RMW
> @@ -140,6 +141,10 @@ config LOCKDEP_SUPPORT
> bool
> default y
>
> +config STACKTRACE_SUPPORT
> + bool
> + default y
> +
> # MACH_LOONGSON32 and MACH_LOONGSON64 are delibrately carried over from the
> # MIPS Loongson code, to preserve Loongson-specific code paths in drivers that
> # are shared between architectures, and specifically expecting the symbols.
> diff --git a/arch/loongarch/include/asm/processor.h b/arch/loongarch/include/asm/processor.h
> index 57ec45aa078e..1c4b4308378d 100644
> --- a/arch/loongarch/include/asm/processor.h
> +++ b/arch/loongarch/include/asm/processor.h
> @@ -101,6 +101,10 @@ struct thread_struct {
> unsigned long reg23, reg24, reg25, reg26; /* s0-s3 */
> unsigned long reg27, reg28, reg29, reg30, reg31; /* s4-s8 */
>
> + /* __schedule() return address / call frame address */
> + unsigned long sched_ra;
> + unsigned long sched_cfa;
> +
> /* CSR registers */
> unsigned long csr_prmd;
> unsigned long csr_crmd;
> @@ -129,6 +133,9 @@ struct thread_struct {
> struct loongarch_fpu fpu FPU_ALIGN;
> };
>
> +#define thread_saved_ra(tsk) (tsk->thread.sched_ra)
> +#define thread_saved_fp(tsk) (tsk->thread.sched_cfa)
> +
> #define INIT_THREAD { \
> /* \
> * Main processor registers \
> @@ -145,6 +152,8 @@ struct thread_struct {
> .reg29 = 0, \
> .reg30 = 0, \
> .reg31 = 0, \
> + .sched_ra = 0, \
> + .sched_cfa = 0, \
> .csr_crmd = 0, \
> .csr_prmd = 0, \
> .csr_euen = 0, \
> diff --git a/arch/loongarch/include/asm/switch_to.h b/arch/loongarch/include/asm/switch_to.h
> index 2a8d04375574..43a5ab162d38 100644
> --- a/arch/loongarch/include/asm/switch_to.h
> +++ b/arch/loongarch/include/asm/switch_to.h
> @@ -15,12 +15,15 @@ struct task_struct;
> * @prev: The task previously executed.
> * @next: The task to begin executing.
> * @next_ti: task_thread_info(next).
> + * @sched_ra: __schedule return address.
> + * @sched_cfa: __schedule call frame address.
> *
> * This function is used whilst scheduling to save the context of prev & load
> * the context of next. Returns prev.
> */
> extern asmlinkage struct task_struct *__switch_to(struct task_struct *prev,
> - struct task_struct *next, struct thread_info *next_ti);
> + struct task_struct *next, struct thread_info *next_ti,
> + void *sched_ra, void *sched_cfa);
>
> /*
> * For newly created kernel threads switch_to() will return to
> @@ -28,10 +31,11 @@ extern asmlinkage struct task_struct *__switch_to(struct task_struct *prev,
> * That is, everything following __switch_to() will be skipped for new threads.
> * So everything that matters to new threads should be placed before __switch_to().
> */
> -#define switch_to(prev, next, last) \
> -do { \
> - lose_fpu_inatomic(1, prev); \
> - (last) = __switch_to(prev, next, task_thread_info(next)); \
> +#define switch_to(prev, next, last) \
> +do { \
> + lose_fpu_inatomic(1, prev); \
> + (last) = __switch_to(prev, next, task_thread_info(next), \
> + __builtin_return_address(0), __builtin_frame_address(0)); \
> } while (0)
>
> #endif /* _ASM_SWITCH_TO_H */
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index 918600e7b30f..7449513eb08d 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -15,6 +15,7 @@ obj-$(CONFIG_EFI) += efi.o
> obj-$(CONFIG_CPU_HAS_FPU) += fpu.o
>
> obj-$(CONFIG_MODULES) += module.o module-sections.o
> +obj-$(CONFIG_STACKTRACE) += stacktrace.o
>
> obj-$(CONFIG_PROC_FS) += proc.o
>
> diff --git a/arch/loongarch/kernel/asm-offsets.c b/arch/loongarch/kernel/asm-offsets.c
> index 20cd9e16a95a..eb350f3ffae5 100644
> --- a/arch/loongarch/kernel/asm-offsets.c
> +++ b/arch/loongarch/kernel/asm-offsets.c
> @@ -103,6 +103,8 @@ void output_thread_defines(void)
> OFFSET(THREAD_REG29, task_struct, thread.reg29);
> OFFSET(THREAD_REG30, task_struct, thread.reg30);
> OFFSET(THREAD_REG31, task_struct, thread.reg31);
> + OFFSET(THREAD_SCHED_RA, task_struct, thread.sched_ra);
> + OFFSET(THREAD_SCHED_CFA, task_struct, thread.sched_cfa);
> OFFSET(THREAD_CSRCRMD, task_struct,
> thread.csr_crmd);
> OFFSET(THREAD_CSRPRMD, task_struct,
> diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
> index 709b7a1664f8..34c3f2148714 100644
> --- a/arch/loongarch/kernel/process.c
> +++ b/arch/loongarch/kernel/process.c
> @@ -135,6 +135,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
> childregs = (struct pt_regs *) childksp - 1;
> /* Put the stack after the struct pt_regs. */
> childksp = (unsigned long) childregs;
> + p->thread.sched_cfa = 0;
> p->thread.csr_euen = 0;
> p->thread.csr_crmd = csr_read32(LOONGARCH_CSR_CRMD);
> p->thread.csr_prmd = csr_read32(LOONGARCH_CSR_PRMD);
> @@ -145,6 +146,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
> p->thread.reg23 = (unsigned long)args->fn;
> p->thread.reg24 = (unsigned long)args->fn_arg;
> p->thread.reg01 = (unsigned long)ret_from_kernel_thread;
> + p->thread.sched_ra = (unsigned long)ret_from_kernel_thread;
> memset(childregs, 0, sizeof(struct pt_regs));
> childregs->csr_euen = p->thread.csr_euen;
> childregs->csr_crmd = p->thread.csr_crmd;
> @@ -161,6 +163,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>
> p->thread.reg03 = (unsigned long) childregs;
> p->thread.reg01 = (unsigned long) ret_from_fork;
> + p->thread.sched_ra = (unsigned long) ret_from_fork;
>
> /*
> * New tasks lose permission to use the fpu. This accelerates context
> diff --git a/arch/loongarch/kernel/stacktrace.c b/arch/loongarch/kernel/stacktrace.c
> new file mode 100644
> index 000000000000..f4f4b8ad3917
> --- /dev/null
> +++ b/arch/loongarch/kernel/stacktrace.c
> @@ -0,0 +1,37 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Stack trace management functions
> + *
> + * Copyright (C) 2022 Loongson Technology Corporation Limited
> + */
> +#include <linux/sched.h>
> +#include <linux/stacktrace.h>
> +
> +#include <asm/stacktrace.h>
> +#include <asm/unwind.h>
> +
> +void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
> + struct task_struct *task, struct pt_regs *regs)
> +{
> + struct pt_regs dummyregs;
> + struct unwind_state state;
> + unsigned long addr;
> +
> + regs = &dummyregs;
> +
> + if (task == current) {
> + regs->csr_era = (unsigned long)__builtin_return_address(0);
> + regs->regs[3] = (unsigned long)__builtin_frame_address(0);
> + } else {
> + regs->csr_era = thread_saved_ra(task);
> + regs->regs[3] = thread_saved_fp(task);
> + }
> +
> + regs->regs[1] = 0;
> + for (unwind_start(&state, task, regs);
> + !unwind_done(&state); unwind_next_frame(&state)) {
> + addr = unwind_get_return_address(&state);
> + if (!addr || !consume_entry(cookie, addr))
> + break;
> + }
> +}
> diff --git a/arch/loongarch/kernel/switch.S b/arch/loongarch/kernel/switch.S
> index 37e84ac8ffc2..43ebbc3990f7 100644
> --- a/arch/loongarch/kernel/switch.S
> +++ b/arch/loongarch/kernel/switch.S
> @@ -21,6 +21,8 @@ SYM_FUNC_START(__switch_to)
>
> cpu_save_nonscratch a0
> stptr.d ra, a0, THREAD_REG01
> + stptr.d a3, a0, THREAD_SCHED_RA
> + stptr.d a4, a0, THREAD_SCHED_CFA
> move tp, a2
> cpu_restore_nonscratch a1
>
> --
> 2.20.1
>
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