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Date: Fri, 22 Oct 2021 18:06:37 +0100
From: Mark Rutland <mark.rutland@....com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: keescook@...omium.org, x86@...nel.org,
linux-kernel@...r.kernel.org, juri.lelli@...hat.com,
vincent.guittot@...aro.org, dietmar.eggemann@....com,
rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
bristot@...hat.com, akpm@...ux-foundation.org,
zhengqi.arch@...edance.com, linux@...linux.org.uk,
catalin.marinas@....com, will@...nel.org, mpe@...erman.id.au,
paul.walmsley@...ive.com, palmer@...belt.com, hca@...ux.ibm.com,
gor@...ux.ibm.com, borntraeger@...ibm.com,
linux-arch@...r.kernel.org, ardb@...nel.org,
"Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>,
broonie@...nel.org
Subject: Re: [PATCH 4/7] arch: Make ARCH_STACKWALK independent of STACKTRACE
On Fri, Oct 22, 2021 at 05:09:37PM +0200, Peter Zijlstra wrote:
> Make arch_stack_walk() available for ARCH_STACKWALK architectures
> without it being entangled in STACKTRACE.
Nice!
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
This looks good to me.
I gave this a spin on arm64, which builds and boots fine with or without
CONFIG_STACKTRACE, and this doesn't seem to regress /proc/*/{wchan,
stack}, so:
Reviewed-by: Mark Rutland <mark.rutland@....com>
Tested-by: Mark Rutland <mark.rutland@....com>
Madhavan (Cc'd) has patches to clean up arm64's various unwinders to use
arch_stack_walk(), and it would be good if we could build atop this
rather than having to unconditionally enable STACKTRACE and expose
/proc/*/stack (which should really just be for debugging the unwinder,
and not something distros should ever have enabled).
Once this settles, would it be possible to place this (and the __sched
change to __switch_to) on a stable branch somewhere?
Thanks,
Mark.
> ---
> arch/arm/kernel/stacktrace.c | 2 --
> arch/arm64/kernel/stacktrace.c | 4 ----
> arch/powerpc/kernel/Makefile | 3 +--
> arch/riscv/kernel/stacktrace.c | 4 ----
> arch/s390/kernel/Makefile | 3 +--
> arch/x86/kernel/Makefile | 2 +-
> include/linux/stacktrace.h | 33 +++++++++++++++++----------------
> 7 files changed, 20 insertions(+), 31 deletions(-)
>
> --- a/arch/arm/kernel/stacktrace.c
> +++ b/arch/arm/kernel/stacktrace.c
> @@ -87,7 +87,6 @@ void notrace walk_stackframe(struct stac
> }
> EXPORT_SYMBOL(walk_stackframe);
>
> -#ifdef CONFIG_STACKTRACE
> noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
> void *cookie, struct task_struct *task,
> struct pt_regs *regs)
> @@ -113,4 +112,3 @@ noinline notrace void arch_stack_walk(st
> break;
> }
> }
> -#endif
> --- a/arch/arm64/kernel/stacktrace.c
> +++ b/arch/arm64/kernel/stacktrace.c
> @@ -216,8 +216,6 @@ void show_stack(struct task_struct *tsk,
> barrier();
> }
>
> -#ifdef CONFIG_STACKTRACE
> -
> noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
> void *cookie, struct task_struct *task,
> struct pt_regs *regs)
> @@ -236,5 +234,3 @@ noinline notrace void arch_stack_walk(st
>
> walk_stackframe(task, &frame, consume_entry, cookie);
> }
> -
> -#endif
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -47,7 +47,7 @@ obj-y := cputable.o syscalls.o \
> udbg.o misc.o io.o misc_$(BITS).o \
> of_platform.o prom_parse.o firmware.o \
> hw_breakpoint_constraints.o interrupt.o \
> - kdebugfs.o
> + kdebugfs.o stacktrace.o
> obj-y += ptrace/
> obj-$(CONFIG_PPC64) += setup_64.o \
> paca.o nvram_64.o note.o
> @@ -116,7 +116,6 @@ obj-$(CONFIG_OPTPROBES) += optprobes.o
> obj-$(CONFIG_KPROBES_ON_FTRACE) += kprobes-ftrace.o
> obj-$(CONFIG_UPROBES) += uprobes.o
> obj-$(CONFIG_PPC_UDBG_16550) += legacy_serial.o udbg_16550.o
> -obj-$(CONFIG_STACKTRACE) += stacktrace.o
> obj-$(CONFIG_SWIOTLB) += dma-swiotlb.o
> obj-$(CONFIG_ARCH_HAS_DMA_SET_MASK) += dma-mask.o
>
> --- a/arch/riscv/kernel/stacktrace.c
> +++ b/arch/riscv/kernel/stacktrace.c
> @@ -139,12 +139,8 @@ unsigned long __get_wchan(struct task_st
> return pc;
> }
>
> -#ifdef CONFIG_STACKTRACE
> -
> noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
> struct task_struct *task, struct pt_regs *regs)
> {
> walk_stackframe(task, regs, consume_entry, cookie);
> }
> -
> -#endif /* CONFIG_STACKTRACE */
> --- a/arch/s390/kernel/Makefile
> +++ b/arch/s390/kernel/Makefile
> @@ -40,7 +40,7 @@ obj-y += sysinfo.o lgr.o os_info.o machi
> obj-y += runtime_instr.o cache.o fpu.o dumpstack.o guarded_storage.o sthyi.o
> obj-y += entry.o reipl.o relocate_kernel.o kdebugfs.o alternative.o
> obj-y += nospec-branch.o ipl_vmparm.o machine_kexec_reloc.o unwind_bc.o
> -obj-y += smp.o text_amode31.o
> +obj-y += smp.o text_amode31.o stacktrace.o
>
> extra-y += head64.o vmlinux.lds
>
> @@ -55,7 +55,6 @@ compat-obj-$(CONFIG_AUDIT) += compat_aud
> obj-$(CONFIG_COMPAT) += compat_linux.o compat_signal.o
> obj-$(CONFIG_COMPAT) += $(compat-obj-y)
> obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
> -obj-$(CONFIG_STACKTRACE) += stacktrace.o
> obj-$(CONFIG_KPROBES) += kprobes.o
> obj-$(CONFIG_KPROBES) += kprobes_insn_page.o
> obj-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace.o
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -84,7 +84,7 @@ obj-$(CONFIG_IA32_EMULATION) += tls.o
> obj-y += step.o
> obj-$(CONFIG_INTEL_TXT) += tboot.o
> obj-$(CONFIG_ISA_DMA_API) += i8237.o
> -obj-$(CONFIG_STACKTRACE) += stacktrace.o
> +obj-y += stacktrace.o
> obj-y += cpu/
> obj-y += acpi/
> obj-y += reboot.o
> --- a/include/linux/stacktrace.h
> +++ b/include/linux/stacktrace.h
> @@ -8,21 +8,6 @@
> struct task_struct;
> struct pt_regs;
>
> -#ifdef CONFIG_STACKTRACE
> -void stack_trace_print(const unsigned long *trace, unsigned int nr_entries,
> - int spaces);
> -int stack_trace_snprint(char *buf, size_t size, const unsigned long *entries,
> - unsigned int nr_entries, int spaces);
> -unsigned int stack_trace_save(unsigned long *store, unsigned int size,
> - unsigned int skipnr);
> -unsigned int stack_trace_save_tsk(struct task_struct *task,
> - unsigned long *store, unsigned int size,
> - unsigned int skipnr);
> -unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
> - unsigned int size, unsigned int skipnr);
> -unsigned int stack_trace_save_user(unsigned long *store, unsigned int size);
> -
> -/* Internal interfaces. Do not use in generic code */
> #ifdef CONFIG_ARCH_STACKWALK
>
> /**
> @@ -75,8 +60,24 @@ int arch_stack_walk_reliable(stack_trace
>
> void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
> const struct pt_regs *regs);
> +#endif /* CONFIG_ARCH_STACKWALK */
>
> -#else /* CONFIG_ARCH_STACKWALK */
> +#ifdef CONFIG_STACKTRACE
> +void stack_trace_print(const unsigned long *trace, unsigned int nr_entries,
> + int spaces);
> +int stack_trace_snprint(char *buf, size_t size, const unsigned long *entries,
> + unsigned int nr_entries, int spaces);
> +unsigned int stack_trace_save(unsigned long *store, unsigned int size,
> + unsigned int skipnr);
> +unsigned int stack_trace_save_tsk(struct task_struct *task,
> + unsigned long *store, unsigned int size,
> + unsigned int skipnr);
> +unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
> + unsigned int size, unsigned int skipnr);
> +unsigned int stack_trace_save_user(unsigned long *store, unsigned int size);
> +
> +#ifndef CONFIG_ARCH_STACKWALK
> +/* Internal interfaces. Do not use in generic code */
> struct stack_trace {
> unsigned int nr_entries, max_entries;
> unsigned long *entries;
>
>
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