Re: [PATCH v4 01/18] arm64: stacktrace: Add shared header for common stack unwinding code

[Kalesh Singh <kaleshsingh@google.com>]

On Mon, Jul 18, 2022 at 5:52 AM Russell King (Oracle)
<linux@armlinux.org.uk> wrote:
>
> Hi,
>
> Can you please explain why you are targetting my @oracle.com email
> address with this patch set?
>
> This causes me problems as I use Outlook's Web interface for that
> which doesn't appear to cope with the threading, and most certainly
> is only capable of top-reply only which is against Linux kernel email
> standards.

Hi Russell,

Sorry I wasn't aware of it (I got your oracle email from
get_maintainer script). Going forward I'll use the one you responded
from instead.

Thanks,
Kalesh

>
> Thanks.
>
> On Thu, Jul 14, 2022 at 11:10:10PM -0700, Kalesh Singh 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@google.com>
> > ---
> >  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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> >
>
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