[Bug binutils/31208] New: strip with no arguments sometimes breaks ELF alignment requirements

[godlygeek at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=31208

            Bug ID: 31208
           Summary: strip with no arguments sometimes breaks ELF alignment
                    requirements
           Product: binutils
           Version: 2.42 (HEAD)
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: godlygeek at gmail dot com
  Target Milestone: ---

Created attachment 15278
  --> https://sourceware.org/bugzilla/attachment.cgi?id=15278&action=edit
A patch to prevent this issue by dropping the unneeded PT_LOAD segment

Reproducer in the form of a published shared library (part of a Python
package):

    mkdir /tmp/strip-bug
    cd /tmp/strip-bug
    wget
https://files.pythonhosted.org/packages/33/6d/bc85b76c79db078597e057a1022b9e5eadebb083840a2942d0cdd0100cb7/memray-1.11.0-cp38-cp38-manylinux_2_12_x86_64.manylinux2010_x86_64.whl
    unzip
memray-1.11.0-cp38-cp38-manylinux_2_12_x86_64.manylinux2010_x86_64.whl
    ldd memray/_memray.cpython-38-x86_64-linux-gnu.so
    strip memray/_memray.cpython-38-x86_64-linux-gnu.so
    ldd memray/_memray.cpython-38-x86_64-linux-gnu.so

The first call to `ldd` will output:

        linux-vdso.so.1 (0x00007ffc3583b000)
        liblz4-c29043df.so.1.7.1 =>
/tmp/strip-bug/memray/../memray.libs/liblz4-c29043df.so.1.7.1
(0x00007f2898b7e000)
        libunwind-92483c07.so.8.0.1 =>
/tmp/strip-bug/memray/../memray.libs/libunwind-92483c07.so.8.0.1
(0x00007f2898964000)
        libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f289894d000)
        libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6
(0x00007f289876b000)
        libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f289861c000)
        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1
(0x00007f28985ff000)
        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0
(0x00007f28985dc000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f28983ea000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f28990a7000)

The second call, after stripping, will output:

        not a dynamic executable

The issue appears to be caused by segment 8 (0-based, as reported by `readelf
-eW`). For the original shared library, that segment is reported as:

  Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz
  Flg Align
  LOAD           0x878000 0x00000000002ff000 0x00000000002ff000 0x00d498
0x00d498 RW  0x1000

After `strip`, that segment shows up as:

  Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz
  Flg Align
  LOAD           0x0f6cfc 0x00000000002ff000 0x00000000002ff000 0x000000
0x000000 RW  0x1000

The file size and memory size have both been dropped to 0, but the alignment
was not dropped from 0x1000 to 0x1, and so the assigned offset of 0x0f6cfc is
incompatible with the declared alignment. This occurs even when compiled from
`master`.

A patch is attached showing a possible solution to this issue.

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