ANNOUNCE: pahole v1.20 (gcc11 DWARF5's default, lots of ELF sections, BTF)

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Hi,
 
	The v1.20 release of pahole and its friends is out, mostly
addressing problems related to gcc 11 defaulting to DWARF5 for -g,
available at the usual places:

Main git repo:

   git://git.kernel.org/pub/scm/devel/pahole/pahole.git

Mirror git repo:

   https://github.com/acmel/dwarves.git

tarball + gpg signature:

   https://fedorapeople.org/~acme/dwarves/dwarves-1.20.tar.xz
   https://fedorapeople.org/~acme/dwarves/dwarves-1.20.tar.bz2
   https://fedorapeople.org/~acme/dwarves/dwarves-1.20.tar.sign

Best Regards,
 
 - Arnaldo

v1.20:

BTF encoder:

  - Improve ELF error reporting using elf_errmsg(elf_errno()).

  - Improve objcopy error handling.

  - Fix handling of 'restrict' qualifier, that was being treated as a 'const'.

  - Support SHN_XINDEX in st_shndx symbol indexes, to handle ELF objects with
    more than 65534 sections, for instance, which happens with kernels built
    with 'KCFLAGS="-ffunction-sections -fdata-sections", Other cases may
    include when using FG-ASLR, LTO.

  - Cope with functions without a name, as seen sometimes when building kernel
    images with some versions of clang, when a SEGFAULT was taking place.

  - Fix BTF variable generation for kernel modules, not skipping variables at
    offset zero.

  - Fix address size to match what is in the ELF file being processed, to fix using
    a 64-bit pahole binary to generate BTF for a 32-bit vmlinux image.

  - Use kernel module ftrace addresses when finding which functions to encode,
    which increases the number of functions encoded.

libbpf:

  - Allow use of packaged version, for distros wanting to dynamically link with
    the system's libbpf package instead of using the libbpf git submodule shipped
    in pahole's source code.

DWARF loader:

  - Support DW_AT_data_bit_offset

    This appeared in DWARF4 but is supported only in gcc's -gdwarf-5,
    support it in a way that makes the output be the same for both cases.

      $ gcc -gdwarf-5 -c examples/dwarf5/bf.c
      $ pahole bf.o
      struct pea {
            long int                   a:1;                  /*     0: 0  8 */
            long int                   b:1;                  /*     0: 1  8 */
            long int                   c:1;                  /*     0: 2  8 */

            /* XXX 29 bits hole, try to pack */
            /* Bitfield combined with next fields */

            int                        after_bitfield;       /*     4     4 */

            /* size: 8, cachelines: 1, members: 4 */
            /* sum members: 4 */
            /* sum bitfield members: 3 bits, bit holes: 1, sum bit holes: 29 bits */
            /* last cacheline: 8 bytes */
      };

  - DW_FORM_implicit_const in attr_numeric() and attr_offset()

  - Support DW_TAG_GNU_call_site, its the standardized rename of the previously supported
    DW_TAG_GNU_call_site.

build:

    - Fix compilation on 32-bit architectures.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>