[Bug ld/28743] -z relro creats holes in the process image on GNU/Linux

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28743

--- Comment #15 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot 
gnu.org> ---
The master branch has been updated by H.J. Lu <hjl@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2f83249c13d86065b4c7cdb198ea871017b4bba1

commit 2f83249c13d86065b4c7cdb198ea871017b4bba1
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Mon Jan 10 15:26:18 2022 -0800

    elf: Remove the 1-page gap before the RELRO segment

    The existing RELRO scheme may leave a 1-page gap before the RELRO segment
    and align the end of the RELRO segment to the page size:

      [18] .eh_frame    PROGBITS    408fa0 008fa0 005e80 00   A  0   0  8
      [19] .init_array  INIT_ARRAY  410de0 00fde0 000008 08  WA  0   0  8
      [20] .fini_array  FINI_ARRAY  410de8 00fde8 000008 08  WA  0   0  8
      [21] .dynamic     DYNAMIC     410df0 00fdf0 000200 10  WA  7   0  8
      [22] .got         PROGBITS    410ff0 00fff0 000010 08  WA  0   0  8
      [23] .got.plt     PROGBITS    411000 010000 000048 08  WA  0   0  8

    Instead, we can remove the 1-page gap if the maximum page size >= the
    maximum section alignment:

      [18] .eh_frame    PROGBITS    408fa0 008fa0 005e80 00   A  0   0  8
      [19] .init_array  INIT_ARRAY  40fde0 00fde0 000008 08  WA  0   0  8
      [20] .fini_array  FINI_ARRAY  40fde8 00fde8 000008 08  WA  0   0  8
      [21] .dynamic     DYNAMIC     40fdf0 00fdf0 000200 10  WA  7   0  8
      [22] .got         PROGBITS    40fff0 00fff0 000010 08  WA  0   0  8
      [23] .got.plt     PROGBITS    410000 010000 000048 08  WA  0   0  8

    Because the end of the RELRO segment is always aligned to the page size
    and may not be moved, the RELRO segment size may be increased:

      [ 3] .dynstr      STRTAB      000148 000148 000001 00   A  0   0  1
      [ 4] .eh_frame    PROGBITS    000150 000150 000000 00   A  0   0  8
      [ 5] .init_array  INIT_ARRAY  200150 000150 000010 08  WA  0   0  1
      [ 6] .fini_array  FINI_ARRAY  200160 000160 000010 08  WA  0   0  1
      [ 7] .jcr         PROGBITS    200170 000170 000008 00  WA  0   0  1
      [ 8] .data.rel.ro PROGBITS    200180 000180 000020 00  WA  0   0 16
      [ 9] .dynamic     DYNAMIC     2001a0 0001a0 0001c0 10  WA  3   0  8
      [10] .got         PROGBITS    200360 000360 0002a8 00  WA  0   0  8
      [11] .bss         NOBITS      201000 000608 000840 00  WA  0   0  1

    vs the old section layout:

      [ 3] .dynstr      STRTAB      000148 000148 000001 00   A  0   0  1
      [ 4] .eh_frame    PROGBITS    000150 000150 000000 00   A  0   0  8
      [ 5] .init_array  INIT_ARRAY  200b48 000b48 000010 08  WA  0   0  1
      [ 6] .fini_array  FINI_ARRAY  200b58 000b58 000010 08  WA  0   0  1
      [ 7] .jcr         PROGBITS    200b68 000b68 000008 00  WA  0   0  1
      [ 8] .data.rel.ro PROGBITS    200b70 000b70 000020 00  WA  0   0 16
      [ 9] .dynamic     DYNAMIC     200b90 000b90 0001c0 10  WA  3   0  8
      [10] .got         PROGBITS    200d50 000d50 0002a8 00  WA  0   0  8
      [11] .bss         NOBITS      201000 000ff8 000840 00  WA  0   0  1

    But there is no 1-page gap.

            PR ld/28743
            * ldlang.c (lang_size_relro_segment_1): Remove the 1-page gap
            before the RELRO segment if the maximum page size >= the maximum
            section alignment.
            * testsuite/ld-i386/pr20830.d: Adjusted.
            * testsuite/ld-s390/gotreloc_64-relro-1.dd: Likewise.
            * testsuite/ld-x86-64/pr14207.d: Likewise.
            * testsuite/ld-x86-64/pr18176.d: Likewise.
            * testsuite/ld-x86-64/pr20830a-now.d: Likewise.
            * testsuite/ld-x86-64/pr20830a.d: Likewise.
            * testsuite/ld-x86-64/pr20830b-now.d: Likewise.
            * testsuite/ld-x86-64/pr20830b.d: Likewise.
            * testsuite/ld-x86-64/pr21038a-now.d: Likewise.
            * testsuite/ld-x86-64/pr21038a.d: Likewise.
            * testsuite/ld-x86-64/pr21038b-now.d: Likewise.
            * testsuite/ld-x86-64/pr21038c-now.d: Likewise.
            * testsuite/ld-x86-64/pr21038c.d: Likewise.

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