[Bug libc/23441] New: sh (SuperH) generates TEXTRELs for PIE binaries due to PIC-incompatible assembly code.

["slyfox at inbox dot ru" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=23441

            Bug ID: 23441
           Summary: sh (SuperH) generates TEXTRELs for PIE binaries due to
                    PIC-incompatible assembly code.
           Product: glibc
           Version: 2.28
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: slyfox at inbox dot ru
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

Minimal reproducer:

  $ echo 'int main(){}' | sh4-unknown-linux-gnu-gcc-8.1.0 -fPIE -pie -x c - -o
a.out -ggdb3 -Wl,-z,text
  /usr/libexec/gcc/sh4-unknown-linux-gnu/ld: read-only segment has dynamic
relocations.
  collect2: error: ld returned 1 exit status

Analysis:
    $ echo 'int main(){}' | sh4-unknown-linux-gnu-gcc-8.1.0 -fPIE -pie -x c -
-o a.out -ggdb3
    $ objdump -d -R a.out | fgrep -C30 R_SH_

000003f8 <_start>:
 3f8:   00 ee           mov     #0,r14
 3fa:   f6 65           mov.l   @r15+,r5
 3fc:   f3 66           mov     r15,r6
 3fe:   46 2f           mov.l   r4,@-r15
 400:   06 d0           mov.l   41c <_start+0x24>,r0    ! 5cc <__libc_csu_fini>
 402:   06 2f           mov.l   r0,@-r15
 404:   03 d4           mov.l   414 <_start+0x1c>,r4    ! 54c <main>
 406:   04 d7           mov.l   418 <_start+0x20>,r7    ! 564 <__libc_csu_init>
 408:   05 d1           mov.l   420 <_start+0x28>,r1    ! 0
 40a:   0b 41           jsr     @r1
 40c:   09 00           nop     
 40e:   05 d1           mov.l   424 <_start+0x2c>,r1    ! 0
 410:   0b 41           jsr     @r1
 412:   09 00           nop     
 414:   4c 05           mov.b   @(r0,r4),r5
                        414: R_SH_RELATIVE      *ABS*+0x54c
 416:   00 00           .word 0x0000
 418:   64 05           mov.b   r6,@(r0,r5)
                        418: R_SH_RELATIVE      *ABS*+0x564
 41a:   00 00           .word 0x0000
 41c:   cc 05           mov.b   @(r0,r12),r5
                        41c: R_SH_RELATIVE      *ABS*+0x5cc
        ...
                        420: R_SH_DIR32 __libc_start_main@GLIBC_2.2
                        424: R_SH_DIR32 abort@GLIBC_2.2

Note: _start symbol refers to abort, __libc_start_main via dynamic relocation
right in .text section:
   
https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/sh/start.S;h=f52077abca02fd624b22d8477b1a4406d7094a1d;hb=HEAD#l91

Ideally it ought to go through GOT+PLT mechanism (if possible) and not store
absolute address in the .text section.

Thanks!

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