[Bug ld/22393] Add read-only segment

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=22393

--- Comment #2 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 <address@hidden>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=2888249fc9eb38b6d6e4bd969ce63c26e3753d5e

commit 2888249fc9eb38b6d6e4bd969ce63c26e3753d5e
Author: H.J. Lu <address@hidden>
Date:   Thu Jan 11 19:04:55 2018 -0800

    ld: Create a new LOAD segment for separate code segment

    When generating separate code LOAD segment, create a new LOAD segment
    if the previous section contains text and the current section doesn't
    or vice versa:

    Elf file type is DYN (Shared object file)
    Entry point 0x200020
    There are 7 program headers, starting at offset 52

    Program Headers:
      Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
      LOAD           0x000000 0x00000000 0x00000000 0x00200 0x00200 R  
0x200000
      LOAD           0x200000 0x00200000 0x00200000 0x00036 0x00036 R E
0x200000
      LOAD           0x400000 0x00400000 0x00400000 0x00064 0x00064 R  
0x200000
      LOAD           0x400f80 0x00600f80 0x00600f80 0x000a0 0x000a0 RW 
0x200000
      DYNAMIC        0x400f80 0x00600f80 0x00600f80 0x00080 0x00080 RW  0x4
      GNU_STACK      0x000000 0x00000000 0x00000000 0x00000 0x00000 RW  0x10
      GNU_RELRO      0x400f80 0x00600f80 0x00600f80 0x00080 0x00080 R   0x1

     Section to Segment mapping:
      Segment Sections...
       00     .hash .gnu.hash .dynsym .dynstr .rela.plt
       01     .plt .text
       02     .rodata .eh_frame
       03     .dynamic .got.plt
       04     .dynamic
       05
       06     .dynamic

    to prevent fetching or executing data in code pages as instructions.

    Also don't put a writable section in a read-only segment if there is a
    RELRO segment.

    Since code segment is aligned and padded to the maximum page size on
    disk, the minimum file size is bigger than the maximum page size which
    is 2MB (0x200000):

    -rwxr-xr-x 1 hjl hjl 4201932 Jan 10 10:41 libfoo.so

    "-z max-page-size=0x1000" can be used to reduce the maximum page size to
    4KB (0x1000):

    -rwxr-xr-x 1 hjl hjl   15820 Jan 10 10:44 libfoo.so

        PR ld/22393
        * elf.c (_bfd_elf_map_sections_to_segments): When generating
        separate code and read-only data LOAD segments, create a new
        LOAD segment if the previous section contains text and the
        current section doesn't or vice versa.  Don't put a writable
        section in a read-only segment if there is a RELRO segment.

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