[Bug ld/23428] ld does not put program headers in a code-only load segment

[nsz at port70 dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=23428

--- Comment #14 from nsz at port70 dot net ---
> @Szabolcs: If you rebuild gcc-8 on Debian testing with "--enable-cet=auto"
> added to CONFARGS in debian/rules2, then you should be able to reproduce the
> musl-gcc crash (after removing the --build-id workaround from 
> musl-gcc.specs!).
> 
> (It appears that "--enable-cet=auto" is the important difference between 
> Arch's
> and Debian's GCC packages.)

thanks, i could reproduce the issue:

it seems ld tries to add a dummy .note.gnu.property to force the
program headers into a load segment, but if there is already a
.note.gnu.property in some of the input object files then it just
tries to merge those and don't add a dummy note at all, however
the merging rules may produce an empty note in the end and then
the note section is dropped.

# cat i.c
int i;
# gcc -fcf-protection=full -c i.c
# readelf -n i.o

Displaying notes found in: .note.gnu.property
  Owner                 Data size       Description
  GNU                  0x00000010       NT_GNU_PROPERTY_TYPE_0
      Properties: x86 feature: IBT, SHSTK
# cat t.s
.globl _start
_start:
  ret
# gcc -c t.s
# ld t.o
# readelf -ln a.out

Elf file type is EXEC (Executable file)
Entry point 0x401000
There are 3 program headers, starting at offset 64

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000000000 0x0000000000400000 0x0000000000400000
                 0x0000000000000108 0x0000000000000108  R      0x1000
  LOAD           0x0000000000001000 0x0000000000401000 0x0000000000401000
                 0x0000000000000001 0x0000000000000001  R E    0x1000
  NOTE           0x00000000000000e8 0x00000000004000e8 0x00000000004000e8
                 0x0000000000000020 0x0000000000000020  R      0x8

 Section to Segment mapping:
  Segment Sections...
   00     .note.gnu.property 
   01     .text 
   02     .note.gnu.property 

Displaying notes found in: .note.gnu.property
  Owner                 Data size       Description
  GNU                  0x00000010       NT_GNU_PROPERTY_TYPE_0
      Properties: x86 ISA used: i486
# ld t.o i.o
# readelf -ln a.out

Elf file type is EXEC (Executable file)
Entry point 0x401000
There are 3 program headers, starting at offset 64

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000001000 0x0000000000401000 0x0000000000401000
                 0x0000000000000001 0x0000000000000001  R E    0x1000
  LOAD           0x0000000000002000 0x0000000000402000 0x0000000000402000
                 0x0000000000000000 0x0000000000000008  RW     0x1000
  GNU_STACK      0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000000 0x0000000000000000  RWE    0x10

 Section to Segment mapping:
  Segment Sections...
   00     .text 
   01     .bss 
   02

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