linux-kernel - Re: [RFC PATCH v3 05/22] objtool: Reorganize ORC types

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Message-ID: <a1b83a8d621e37310194c0c32b9d847a0952d282.camel@gmail.com>
Date:   Sat, 18 Feb 2023 17:30:20 +0800
From:   Suraj Jitindar Singh <sjitindarsingh@...il.com>
To:     madvenka@...ux.microsoft.com, jpoimboe@...hat.com,
        peterz@...radead.org, chenzhongjin@...wei.com,
        mark.rutland@....com, broonie@...nel.org, nobuta.keiya@...itsu.com,
        catalin.marinas@....com, will@...nel.org,
        jamorris@...ux.microsoft.com, linux-arm-kernel@...ts.infradead.org,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v3 05/22] objtool: Reorganize ORC types

On Thu, 2023-02-02 at 01:40 -0600, madvenka@...ux.microsoft.com wrote:
> From: "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>
> 
> The ORC code needs to be reorganized into arch-specific and generic
> parts
> so that architectures other than X86 can use the generic parts.
> 
> orc_types.h contains the following ORC definitions shared between
> objtool
> and the kernel:
> 
> 	- ORC register definitions which are arch-specific.
> 	- orc_entry structure which is generic.
> 
> Move orc_entry into a new file include/linux/orc_entry.h. Also, the
> field
> names bp_reg and bp_offset in struct orc_entry are x86-specific.
> Change
> them to fp_reg and fp_offset. FP stands for frame pointer.
> 
> Currently, the type field in orc_entry is only 2 bits. For other
> architectures, we will need more. So, expand this to 3 bits.
> 
> Signed-off-by: Madhavan T. Venkataraman <madvenka@...ux.microsoft.com
> >
> ---
>  arch/x86/include/asm/orc_types.h       | 37 +++++-------------------
>  include/linux/orc_entry.h              | 39
> ++++++++++++++++++++++++++
>  tools/arch/x86/include/asm/orc_types.h | 37 +++++-------------------
>  tools/include/linux/orc_entry.h        | 39
> ++++++++++++++++++++++++++
>  tools/objtool/orc_gen.c                |  4 +--
>  tools/objtool/sync-check.sh            |  1 +
>  6 files changed, 95 insertions(+), 62 deletions(-)
>  create mode 100644 include/linux/orc_entry.h
>  create mode 100644 tools/include/linux/orc_entry.h
> 

[snip]

> diff --git a/tools/include/linux/orc_entry.h
> b/tools/include/linux/orc_entry.h
> new file mode 100644
> index 000000000000..3d49e3b9dabe
> --- /dev/null
> +++ b/tools/include/linux/orc_entry.h
> @@ -0,0 +1,39 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@...hat.com>
> + */
> +
> +#ifndef _ORC_ENTRY_H
> +#define _ORC_ENTRY_H
> +
> +#ifndef __ASSEMBLY__
> +#include <asm/byteorder.h>
> +
> +/*
> + * This struct is more or less a vastly simplified version of the
> DWARF Call
> + * Frame Information standard.  It contains only the necessary parts
> of DWARF
> + * CFI, simplified for ease of access by the in-kernel unwinder.  It
> tells the
> + * unwinder how to find the previous SP and BP (and sometimes entry
> regs) on
> + * the stack for a given code address.  Each instance of the struct
> corresponds
> + * to one or more code locations.
> + */
> +struct orc_entry {
> +	s16		sp_offset;
> +	s16		fp_offset;
> +#if defined(__LITTLE_ENDIAN_BITFIELD)
> +	unsigned	sp_reg:4;
> +	unsigned	fp_reg:4;
> +	unsigned	type:3;
> +	unsigned	end:1;
> +#elif defined(__BIG_ENDIAN_BITFIELD)
> +	unsigned	fp_reg:4;
> +	unsigned	sp_reg:4;
> +	unsigned	unused:4;
> +	unsigned	end:1;
> +	unsigned	type:3;
> +#

nit:
I believe you also need to update fp_reg/bp_offset -> fp_reg/fp_offset
in orc_dump() in orc_dump.c

- Suraj

> +
> +#endif /* __ASSEMBLY__ */
> +
> +#endif /* _ORC_ENTRY_H */
> diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
> index dd3c64af9db2..68c317daadbf 100644
> --- a/tools/objtool/orc_gen.c
> +++ b/tools/objtool/orc_gen.c
> @@ -98,7 +98,7 @@ static int write_orc_entry(struct elf *elf, struct
> section *orc_sec,
>  	orc = (struct orc_entry *)orc_sec->data->d_buf + idx;
>  	memcpy(orc, o, sizeof(*orc));
>  	orc->sp_offset = bswap_if_needed(orc->sp_offset);
> -	orc->bp_offset = bswap_if_needed(orc->bp_offset);
> +	orc->fp_offset = bswap_if_needed(orc->fp_offset);
>  
>  	/* populate reloc for ip */
>  	if (elf_add_reloc_to_insn(elf, ip_sec, idx * sizeof(int),
> R_X86_64_PC32,
> @@ -149,7 +149,7 @@ int orc_create(struct objtool_file *file)
>  
>  	struct orc_entry null = {
>  		.sp_reg  = ORC_REG_UNDEFINED,
> -		.bp_reg  = ORC_REG_UNDEFINED,
> +		.fp_reg  = ORC_REG_UNDEFINED,
>  		.type    = UNWIND_HINT_TYPE_CALL,
>  	};
>  
> diff --git a/tools/objtool/sync-check.sh b/tools/objtool/sync-
> check.sh
> index ee49b4e9e72c..ef1acb064605 100755
> --- a/tools/objtool/sync-check.sh
> +++ b/tools/objtool/sync-check.sh
> @@ -18,6 +18,7 @@ arch/x86/include/asm/unwind_hints.h
>  arch/x86/lib/x86-opcode-map.txt
>  arch/x86/tools/gen-insn-attr-x86.awk
>  include/linux/static_call_types.h
> +include/linux/orc_entry.h
>  "
>  
>  SYNC_CHECK_FILES='