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Date: Fri, 15 Jul 2022 14:58:27 +0100
From: Fuad Tabba <tabba@...gle.com>
To: Kalesh Singh <kaleshsingh@...gle.com>
Cc: maz@...nel.org, mark.rutland@....com, broonie@...nel.org,
madvenka@...ux.microsoft.com, will@...nel.org, qperret@...gle.com,
james.morse@....com, alexandru.elisei@....com,
suzuki.poulose@....com, catalin.marinas@....com,
andreyknvl@...il.com, russell.king@...cle.com,
vincenzo.frascino@....com, mhiramat@...nel.org, ast@...nel.org,
drjones@...hat.com, wangkefeng.wang@...wei.com, elver@...gle.com,
keirf@...gle.com, yuzenghui@...wei.com, ardb@...nel.org,
oupton@...gle.com, linux-arm-kernel@...ts.infradead.org,
kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
android-mm@...gle.com, kernel-team@...roid.com
Subject: Re: [PATCH v4 01/18] arm64: stacktrace: Add shared header for common
stack unwinding code
Hi Kalesh,
On Fri, Jul 15, 2022 at 7:10 AM Kalesh Singh <kaleshsingh@...gle.com> wrote:
>
> In order to reuse the arm64 stack unwinding logic for the nVHE
> hypervisor stack, move the common code to a shared header
> (arch/arm64/include/asm/stacktrace/common.h).
>
> The nVHE hypervisor cannot safely link against kernel code, so we
> make use of the shared header to avoid duplicated logic later in
> this series.
>
> Signed-off-by: Kalesh Singh <kaleshsingh@...gle.com>
> ---
Reviewed-by: Fuad Tabba <tabba@...gle.com>
Thanks,
/fuad
> arch/arm64/include/asm/stacktrace.h | 35 +------
> arch/arm64/include/asm/stacktrace/common.h | 105 +++++++++++++++++++++
> arch/arm64/kernel/stacktrace.c | 57 -----------
> 3 files changed, 106 insertions(+), 91 deletions(-)
> create mode 100644 arch/arm64/include/asm/stacktrace/common.h
>
> diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
> index aec9315bf156..79f455b37c84 100644
> --- a/arch/arm64/include/asm/stacktrace.h
> +++ b/arch/arm64/include/asm/stacktrace.h
> @@ -8,52 +8,19 @@
> #include <linux/percpu.h>
> #include <linux/sched.h>
> #include <linux/sched/task_stack.h>
> -#include <linux/types.h>
> #include <linux/llist.h>
>
> #include <asm/memory.h>
> #include <asm/ptrace.h>
> #include <asm/sdei.h>
>
> -enum stack_type {
> - STACK_TYPE_UNKNOWN,
> - STACK_TYPE_TASK,
> - STACK_TYPE_IRQ,
> - STACK_TYPE_OVERFLOW,
> - STACK_TYPE_SDEI_NORMAL,
> - STACK_TYPE_SDEI_CRITICAL,
> - __NR_STACK_TYPES
> -};
> -
> -struct stack_info {
> - unsigned long low;
> - unsigned long high;
> - enum stack_type type;
> -};
> +#include <asm/stacktrace/common.h>
>
> extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
> const char *loglvl);
>
> DECLARE_PER_CPU(unsigned long *, irq_stack_ptr);
>
> -static inline bool on_stack(unsigned long sp, unsigned long size,
> - unsigned long low, unsigned long high,
> - enum stack_type type, struct stack_info *info)
> -{
> - if (!low)
> - return false;
> -
> - if (sp < low || sp + size < sp || sp + size > high)
> - return false;
> -
> - if (info) {
> - info->low = low;
> - info->high = high;
> - info->type = type;
> - }
> - return true;
> -}
> -
> static inline bool on_irq_stack(unsigned long sp, unsigned long size,
> struct stack_info *info)
> {
> diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
> new file mode 100644
> index 000000000000..64ae4f6b06fe
> --- /dev/null
> +++ b/arch/arm64/include/asm/stacktrace/common.h
> @@ -0,0 +1,105 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Common arm64 stack unwinder code.
> + *
> + * Copyright (C) 2012 ARM Ltd.
> + */
> +#ifndef __ASM_STACKTRACE_COMMON_H
> +#define __ASM_STACKTRACE_COMMON_H
> +
> +#include <linux/bitmap.h>
> +#include <linux/bitops.h>
> +#include <linux/types.h>
> +
> +enum stack_type {
> + STACK_TYPE_UNKNOWN,
> + STACK_TYPE_TASK,
> + STACK_TYPE_IRQ,
> + STACK_TYPE_OVERFLOW,
> + STACK_TYPE_SDEI_NORMAL,
> + STACK_TYPE_SDEI_CRITICAL,
> + __NR_STACK_TYPES
> +};
> +
> +struct stack_info {
> + unsigned long low;
> + unsigned long high;
> + enum stack_type type;
> +};
> +
> +/*
> + * A snapshot of a frame record or fp/lr register values, along with some
> + * accounting information necessary for robust unwinding.
> + *
> + * @fp: The fp value in the frame record (or the real fp)
> + * @pc: The lr value in the frame record (or the real lr)
> + *
> + * @stacks_done: Stacks which have been entirely unwound, for which it is no
> + * longer valid to unwind to.
> + *
> + * @prev_fp: The fp that pointed to this frame record, or a synthetic value
> + * of 0. This is used to ensure that within a stack, each
> + * subsequent frame record is at an increasing address.
> + * @prev_type: The type of stack this frame record was on, or a synthetic
> + * value of STACK_TYPE_UNKNOWN. This is used to detect a
> + * transition from one stack to another.
> + *
> + * @kr_cur: When KRETPROBES is selected, holds the kretprobe instance
> + * associated with the most recently encountered replacement lr
> + * value.
> + *
> + * @task: The task being unwound.
> + */
> +struct unwind_state {
> + unsigned long fp;
> + unsigned long pc;
> + DECLARE_BITMAP(stacks_done, __NR_STACK_TYPES);
> + unsigned long prev_fp;
> + enum stack_type prev_type;
> +#ifdef CONFIG_KRETPROBES
> + struct llist_node *kr_cur;
> +#endif
> + struct task_struct *task;
> +};
> +
> +static inline bool on_stack(unsigned long sp, unsigned long size,
> + unsigned long low, unsigned long high,
> + enum stack_type type, struct stack_info *info)
> +{
> + if (!low)
> + return false;
> +
> + if (sp < low || sp + size < sp || sp + size > high)
> + return false;
> +
> + if (info) {
> + info->low = low;
> + info->high = high;
> + info->type = type;
> + }
> + return true;
> +}
> +
> +static inline void unwind_init_common(struct unwind_state *state,
> + struct task_struct *task)
> +{
> + state->task = task;
> +#ifdef CONFIG_KRETPROBES
> + state->kr_cur = NULL;
> +#endif
> +
> + /*
> + * Prime the first unwind.
> + *
> + * In unwind_next() we'll check that the FP points to a valid stack,
> + * which can't be STACK_TYPE_UNKNOWN, and the first unwind will be
> + * treated as a transition to whichever stack that happens to be. The
> + * prev_fp value won't be used, but we set it to 0 such that it is
> + * definitely not an accessible stack address.
> + */
> + bitmap_zero(state->stacks_done, __NR_STACK_TYPES);
> + state->prev_fp = 0;
> + state->prev_type = STACK_TYPE_UNKNOWN;
> +}
> +
> +#endif /* __ASM_STACKTRACE_COMMON_H */
> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
> index fcaa151b81f1..94a5dd2ab8fd 100644
> --- a/arch/arm64/kernel/stacktrace.c
> +++ b/arch/arm64/kernel/stacktrace.c
> @@ -18,63 +18,6 @@
> #include <asm/stack_pointer.h>
> #include <asm/stacktrace.h>
>
> -/*
> - * A snapshot of a frame record or fp/lr register values, along with some
> - * accounting information necessary for robust unwinding.
> - *
> - * @fp: The fp value in the frame record (or the real fp)
> - * @pc: The lr value in the frame record (or the real lr)
> - *
> - * @stacks_done: Stacks which have been entirely unwound, for which it is no
> - * longer valid to unwind to.
> - *
> - * @prev_fp: The fp that pointed to this frame record, or a synthetic value
> - * of 0. This is used to ensure that within a stack, each
> - * subsequent frame record is at an increasing address.
> - * @prev_type: The type of stack this frame record was on, or a synthetic
> - * value of STACK_TYPE_UNKNOWN. This is used to detect a
> - * transition from one stack to another.
> - *
> - * @kr_cur: When KRETPROBES is selected, holds the kretprobe instance
> - * associated with the most recently encountered replacement lr
> - * value.
> - *
> - * @task: The task being unwound.
> - */
> -struct unwind_state {
> - unsigned long fp;
> - unsigned long pc;
> - DECLARE_BITMAP(stacks_done, __NR_STACK_TYPES);
> - unsigned long prev_fp;
> - enum stack_type prev_type;
> -#ifdef CONFIG_KRETPROBES
> - struct llist_node *kr_cur;
> -#endif
> - struct task_struct *task;
> -};
> -
> -static void unwind_init_common(struct unwind_state *state,
> - struct task_struct *task)
> -{
> - state->task = task;
> -#ifdef CONFIG_KRETPROBES
> - state->kr_cur = NULL;
> -#endif
> -
> - /*
> - * Prime the first unwind.
> - *
> - * In unwind_next() we'll check that the FP points to a valid stack,
> - * which can't be STACK_TYPE_UNKNOWN, and the first unwind will be
> - * treated as a transition to whichever stack that happens to be. The
> - * prev_fp value won't be used, but we set it to 0 such that it is
> - * definitely not an accessible stack address.
> - */
> - bitmap_zero(state->stacks_done, __NR_STACK_TYPES);
> - state->prev_fp = 0;
> - state->prev_type = STACK_TYPE_UNKNOWN;
> -}
> -
> /*
> * Start an unwind from a pt_regs.
> *
> --
> 2.37.0.170.g444d1eabd0-goog
>
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