Re: [PATCH 2/3] GDB: Add support for 24 bit addresses

Simon Marchi
2018-08-24T20:34:22Z

(CCing gcc-patches because of the change in include/dwarf2.h)

On 2018-08-23 13:35, John Darrington wrote:
> * include/dwarf2.h (enum dwarf_unit_type)[DW_EH_PE_udata3]: New member.
> * gdb/dwarf2-frame.c (encoding_for_size): Deal with case 3.
> (read_encoded_value): Deal with case DW_EH_PE_udata3
> ---
> gdb/dwarf2-frame.c | 7 ++++++-
> include/dwarf2.h | 5 ++++-
> 2 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c
> index f7dc820f4d..b329e34997 100644
> --- a/gdb/dwarf2-frame.c
> +++ b/gdb/dwarf2-frame.c
> @@ -1527,12 +1527,14 @@ encoding_for_size (unsigned int size)
> {
> case 2:
> return DW_EH_PE_udata2;
> + case 3:
> + return DW_EH_PE_udata3;
> case 4:
> return DW_EH_PE_udata4;
> case 8:
> return DW_EH_PE_udata8;
> default:
> - internal_error (__FILE__, __LINE__, _("Unsupported address
> size"));
> + internal_error (__FILE__, __LINE__, _("Unsupported address size
> %d"), size);
> }
> }
>
> @@ -1605,6 +1607,9 @@ read_encoded_value (struct comp_unit *unit,
> gdb_byte encoding,
> case DW_EH_PE_udata2:
> *bytes_read_ptr += 2;
> return (base + bfd_get_16 (unit->abfd, (bfd_byte *) buf));
> + case DW_EH_PE_udata3:
> + *bytes_read_ptr += 3;
> + return (base + bfd_get_24 (unit->abfd, (bfd_byte *) buf));
> case DW_EH_PE_udata4:
> *bytes_read_ptr += 4;
> return (base + bfd_get_32 (unit->abfd, (bfd_byte *) buf));
> diff --git a/include/dwarf2.h b/include/dwarf2.h
> index cf0039a92a..05c328057b 100644
> --- a/include/dwarf2.h
> +++ b/include/dwarf2.h
> @@ -474,11 +474,14 @@ enum dwarf_unit_type
> #define DW_EH_PE_udata2 0x02
> #define DW_EH_PE_udata4 0x03
> #define DW_EH_PE_udata8 0x04
> +
> +#define DW_EH_PE_udata3 0x05
> +
> +#define DW_EH_PE_signed 0x08
> #define DW_EH_PE_sleb128 0x09
> #define DW_EH_PE_sdata2 0x0A
> #define DW_EH_PE_sdata4 0x0B
> #define DW_EH_PE_sdata8 0x0C
> -#define DW_EH_PE_signed 0x08
>
> #define DW_EH_PE_pcrel 0x10
> #define DW_EH_PE_textrel 0x20

This file is owned by GCC (see the MAINTAINERS file at the top of
binutils-gdb). To get a modification in it, you would need to provide a
patch to gcc, then we can import the change in binutils-gdb.

I am not too sure who is responsible for allocating these values, as
they are not from the DWARF standard. At the very least, there should
be a comment to say what architecture uses this non-standard value. Is
there also a gcc port you are planning to upstream, that would use this
value?

Simon