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

Suraj Jitindar Singh
2023-02-18T09:30:41Z

On Thu, 2023-02-02 at 01:40 -0600, 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.
>
> 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@linux.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@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;
> + 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='