[Bug ld/26378] New: [2.35 regression] incorrect WAX section flags in linker output

[nsz at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26378

            Bug ID: 26378
           Summary: [2.35 regression] incorrect WAX section flags in
                    linker output
           Product: binutils
           Version: 2.35
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: nsz at gcc dot gnu.org
  Target Milestone: ---

since binutils 2.35 i see WAX flags on some nobits sections:

$ cat a.s
.section        .text.foo,"ax",@progbits
.global foo
.type foo,%function
foo:
        ret

$ cat a.ld
SECTIONS {
        .plt (NOLOAD) : { BYTE(0) }
        .text.foo (NOLOAD) : { BYTE(0) }
}

$ as -c -o a.o a.s
$ ld -T a.ld a.o
$ readelf -SW a.out
There are 7 section headers, starting at offset 0x10b0:

Section Headers:
  [Nr] Name              Type            Address          Off    Size   ES Flg
Lk Inf Al
  [ 0]                   NULL            0000000000000000 000000 000000 00     
0   0  0
  [ 1] .text.foo         PROGBITS        0000000000000000 001000 000001 00  AX 
0   0  1
  [ 2] .plt              NOBITS          0000000000000001 001001 000001 00 WAX 
0   0  1
  [ 3] .text.foo         NOBITS          0000000000000002 001001 000001 00 WAX 
0   0  1
  [ 4] .symtab           SYMTAB          0000000000000000 001008 000078 18     
5   4  8
  [ 5] .strtab           STRTAB          0000000000000000 001080 000005 00     
0   0  1
  [ 6] .shstrtab         STRTAB          0000000000000000 001085 00002a 00     
0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
  L (link order), O (extra OS processing required), G (group), T (TLS),
  C (compressed), x (unknown), o (OS specific), E (exclude),
  l (large), p (processor specific)


if i change '.text.foo' to '.test.foo' in a.s and a.ld
then there is no WAX on that section.

i don't see WAX prior to commit

commit 8c803a2dd7d3d742a3d0071914f557ef465afe71
Commit:     Alan Modra <amo...@gmail.com>
CommitDate: 2020-03-02 11:36:19 +1030

    elf_backend_section_flags and _bfd_elf_init_private_section_data


this affects linux kernel modules on aarch64, but the
behaviour change seems to be target independent.

before the commit above i see:

$ readelf -SW a.out
There are 7 section headers, starting at offset 0x10b0:

Section Headers:
  [Nr] Name              Type            Address          Off    Size   ES Flg
Lk Inf Al
  [ 0]                   NULL            0000000000000000 000000 000000 00     
0   0  0
  [ 1] .text.foo         PROGBITS        0000000000000000 001000 000001 00  AX 
0   0  1
  [ 2] .plt              NOBITS          0000000000000001 001001 000001 00  WA 
0   0  1
  [ 3] .text.foo         NOBITS          0000000000000002 001001 000001 00  WA 
0   0  1
  [ 4] .symtab           SYMTAB          0000000000000000 001008 000078 18     
5   4  8
  [ 5] .strtab           STRTAB          0000000000000000 001080 000005 00     
0   0  1
  [ 6] .shstrtab         STRTAB          0000000000000000 001085 00002a 00     
0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
  L (link order), O (extra OS processing required), G (group), T (TLS),
  C (compressed), x (unknown), o (OS specific), E (exclude),
  l (large), p (processor specific)

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