Re: [POC 4/5] sframe: add an SFrame format stack tracer

From: Peter Zijlstra <peterz@infradead.org>
To: Indu Bhagat <indu.bhagat@oracle.com>
Cc: linux-toolchains@vger.kernel.org, daandemeyer@meta.com,
	andrii@kernel.org, rostedt@goodmis.org, kris.van.hees@oracle.com,
	elena.zannoni@oracle.com, nick.alcock@oracle.com
Subject: Re: [POC 4/5] sframe: add an SFrame format stack tracer
Date: Tue, 2 May 2023 10:53:25 +0200	[thread overview]
Message-ID: <20230502085325.GG1597476@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20230501200410.3973453-5-indu.bhagat@oracle.com>

On Mon, May 01, 2023 at 01:04:09PM -0700, Indu Bhagat wrote:
> diff --git a/arch/arm64/include/asm/sframe_regs.h b/arch/arm64/include/asm/sframe_regs.h
> new file mode 100644
> index 000000000000..ae9ab9d5d3c1
> --- /dev/null
> +++ b/arch/arm64/include/asm/sframe_regs.h
> @@ -0,0 +1,37 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2023, Oracle and/or its affiliates.
> + */
> +
> +#ifdef ASM_ARM64_SFRAME_REGS_H
> +#define ASM_ARM64_SFRAME_REGS_H
> +
> +#define STACK_ACCESS_LEN 8
> +
> +static inline uint64_t
> +get_ptregs_ip(struct pt_regs *regs)
> +{
> +	return regs->pc;
> +}
> +
> +static inline uint64_t
> +get_ptregs_sp(struct pt_regs *regs)
> +{
> +	return regs->sp;
> +}
> +
> +static inline uint64_t
> +get_ptregs_fp(struct pt_regs *regs)
> +{
> +#define UNWIND_AARCH64_X29              29      /* 64-bit frame pointer.  */
> +	return (uint64_t)regs->regs[UNWIND_AARCH64_X29];
> +}
> +
> +static inline uint64_t
> +get_ptregs_ra(struct pt_regs *regs)
> +{
> +#define UNWIND_AARCH64_X30              30      /* 64-bit link pointer.  */
> +	return (uint64_t)regs->regs[UNWIND_AARCH64_X30];
> +}
> +
> +#endif /* ASM_ARM64_SFRAME_REGS_H */
> diff --git a/arch/x86/include/asm/sframe_regs.h b/arch/x86/include/asm/sframe_regs.h
> new file mode 100644
> index 000000000000..99f84955854a
> --- /dev/null
> +++ b/arch/x86/include/asm/sframe_regs.h
> @@ -0,0 +1,34 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2023, Oracle and/or its affiliates.
> + */
> +
> +#ifndef ASM_X86_SFRAME_REGS_H
> +#define ASM_X86_SFRAME_REGS_H
> +
> +#define STACK_ACCESS_LEN 8
> +
> +static inline uint64_t
> +get_ptregs_ip(struct pt_regs *regs)
> +{
> +	return (uint64_t)regs->ip;
> +}
> +
> +static inline uint64_t
> +get_ptregs_sp(struct pt_regs *regs)
> +{
> +	return (uint64_t)regs->sp;
> +}
> +
> +static inline uint64_t
> +get_ptregs_fp(struct pt_regs *regs)
> +{
> +	return (uint64_t)regs->bp;
> +}
> +
> +static inline uint64_t
> +get_ptregs_ra(struct pt_regs *regs)
> +{
> +	return 0; /* SFRAME_CFA_FIXED_RA_INVALID */
> +}
> +#endif /* ASM_X86_SFRAME_REGS_H */

arch/*/include/ptrace.h already provides:

  instruction_pointer(regs)
  kernel_stack_pointer(regs)
  frame_pointer(regs)

and on arm64:

  procedure_link_pointer(regs)

That do all this, I would suggest you use those instead of creating yet
another set of wrappers.