Re: [RFC PATCH v2 05/20] objtool: Reorganize ORC types

Chen Zhongjin
2022-05-24T14:27:52Z

On 2022/5/24 8:16, madvenka@linux.microsoft.com wrote:
> From: "Madhavan T. Venkataraman" <madvenka@linux.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.
...
> diff --git a/include/linux/orc_entry.h b/include/linux/orc_entry.h
> new file mode 100644
> index 000000000000..3d49e3b9dabe
> --- /dev/null
> +++ b/include/linux/orc_entry.h
> @@ -0,0 +1,39 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.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;
Are sp_reg & fp_reg & end needed? I noticed that they are not used in
reliability checking.

> + 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;
> +#endif
> +} __packed;
> +
> +#endif /* __ASSEMBLY__ */
> +
> +#endif /* _ORC_ENTRY_H */