[Bug binutils/4007] New: problems with linker / strip / BFD

[etienne_lorrain at yahoo dot fr]

I just want to report that, I do not know if it shall be considered as a bug,
as bad use, as undocumented feature:

 Lets compile some Linux kernel with Fedora 6 default toolchain:
address@hidden ~]$ ld --version
GNU ld version 2.17.50.0.3-6 20060715
address@hidden ~]$ readelf -v
GNU readelf 2.17.50.0.3-6 20060715

address@hidden tmp]$ tar xjf ../linux2/linux-2.6.20.tar.bz2
address@hidden tmp]$ cd linux-2.6.20
address@hidden linux-2.6.20]$ cp ../../linux2/linux-2.6.20-gujin/.config .
address@hidden linux-2.6.20]$ make oldconfig > log
address@hidden linux-2.6.20]$ make vmlinux >> log
... few warnings ...
address@hidden linux-2.6.20]$ readelf -l vmlinux

Elf file type is EXEC (Executable file)
Entry point 0x100000
There are 3 program headers, starting at offset 52

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD           0x001000 0xc0100000 0x00100000 0x3995e0 0x3995e0 R E 0x1000
  LOAD           0x39b000 0xc049a000 0x0049a000 0x75085 0xaf000 RWE 0x1000
  NOTE           0x000000 0x00000000 0x00000000 0x00000 0x00000 R   0x4

 Section to Segment mapping:
  Segment Sections...
   00     .text __ex_table .rodata .pci_fixup __param
   01     .data .data_nosave .data.page_aligned .data.cacheline_aligned
.data.read_mostly
.data.init_task .init.text .init.data .init.setup .initcall.init 
.con_initcall.init
.security_initcall.init .altinstructions .altinstr_replacement .exit.text
.init.ramfs
.bss
   02
address@hidden linux-2.6.20]$

  OK, everything is fine. The ld script affects manually the program header by:
  /* arch/i386/kernel/vmlinux.lds.S */
PHDRS {
        text PT_LOAD FLAGS(5);  /* R_E */
        data PT_LOAD FLAGS(7);  /* RWE */
        note PT_NOTE FLAGS(4);  /* R__ */
}
  And the text section goes to the :text program header, it is linked at a fixed
address.
  .text : AT(ADDR(.text) - LOAD_OFFSET) {
...
  } :text = 0x9090

 Now I want to create another text section - I was thinking that a new program
header would be added or an error message because I create it a another address,
using the patch at sourceforge at:
http://sourceforge.net/project/showfiles.php?group_id=15465&package_id=174813&release_id=482035

The important extract is:
SECTIONS
{
  .realmode 0 : AT (ADDR(.bss) + SIZEOF(.bss) - LOAD_OFFSET) {
     ... all my sections ...
  } :text = 0x9090
  . = 0xc0000000 ; /* or more */
  .text : AT(ADDR(.text) - LOAD_OFFSET) {
     ... original part ...
  } :text = 0x9090


address@hidden linux-2.6.20]$ patch -p1 < ../../linux/gujin-patch-2.6.20-rc5
patching file arch/i386/Kconfig
patching file arch/i386/kernel/Makefile
patching file arch/i386/kernel/realmode.c
patching file arch/i386/kernel/setup.c
patching file arch/i386/kernel/vmlinux.lds.S
patching file arch/i386/Makefile
patching file include/asm-i386/realmode.h
patching file Makefile
patching file scripts/gzcopy.c
patching file scripts/gzparam.c
address@hidden linux-2.6.20]$ make linux-2.6.20.kgz > log

 But nothing change and I do not get any warning or error for a section
containing code not linked to a program header:

address@hidden linux-2.6.20]$ readelf -l vmlinux

Elf file type is EXEC (Executable file)
Entry point 0x100000
There are 3 program headers, starting at offset 52

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD           0x001000 0xc0100000 0x00100000 0x44a830 0x44a830 R E 0x1000
  LOAD           0x44c000 0xc049a000 0x0049a000 0x75085 0xaf000 RWE 0x1000
  NOTE           0x000000 0x00000000 0x00000000 0x00000 0x00000 R   0x4

 Section to Segment mapping:
  Segment Sections...
   00     .bss .text __ex_table .rodata .pci_fixup __param .data .data_nosave
.data.page_aligned .data.cacheline_aligned .data.read_mostly .data.init_task
.init.text
.init.data .init.setup .initcall.init .con_initcall.init .security_initcall.init
.altinstructions .altinstr_replacement .exit.text .init.ramfs
   01     .bss .data .data_nosave .data.page_aligned .data.cacheline_aligned
.data.read_mostly .data.init_task .init.text .init.data .init.setup 
.initcall.init
.con_initcall.init .security_initcall.init .altinstructions 
.altinstr_replacement
.exit.text .init.ramfs
   02
address@hidden linux-2.6.20]$

 And there is something wrong once using strip from this file:

address@hidden linux-2.6.20]$ objcopy -S vmlinux vmlinux.stripped
BFD: vmlinux.stripped: warning: allocated section `.realmode' not in segment
address@hidden linux-2.6.20]$ readelf -l vmlinux.stripped

Elf file type is EXEC (Executable file)
Entry point 0x100000
There are 3 program headers, starting at offset 52

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD           0x001000 0xc0100000 0x00100000 0x40f085 0x449000 R E 0x1000
  LOAD           0x411000 0xc049a000 0x0049a000 0x75085 0xaf000 RWE 0x1000
  NOTE           0x000000 0x00000000 0x00000000 0x00000 0x00000 R   0x4

 Section to Segment mapping:
  Segment Sections...
   00     .bss .text __ex_table .rodata .pci_fixup __param .data .data_nosave
.data.page_aligned .data.cacheline_aligned .data.read_mostly .data.init_task
.init.text
.init.data .init.setup .initcall.init .con_initcall.init .security_initcall.init
.altinstructions .altinstr_replacement .exit.text .init.ramfs
   01     .bss .data .data_nosave .data.page_aligned .data.cacheline_aligned
.data.read_mostly .data.init_task .init.text .init.data .init.setup 
.initcall.init
.con_initcall.init .security_initcall.init .altinstructions 
.altinstr_replacement
.exit.text .init.ramfs
   02
address@hidden linux-2.6.20]$

  Note that the first program header MemSiz overlap the second program header:
0x00100000 + 0x449000 > 0x0049a000
 And the two FileSiz are not aligned so the memset at PhysAddr+FileSiz is done
 at an unaligned address so will be slow.

 I do not know what should be the behaviour, just something seems wrong.



 Something completely different, when using the linux patch I posted on LKM,
where a new program header is created for this section, and is removed if i want
to get rid of the section .realmode completely because I want to generate the
old target, you can ask me the question:
address@hidden linux-2.6.20-gujin]$ objcopy -R .note -R .comment -R .realmode -S
vmlinux vmlinux.tmp
BFD: vmlinux: warning: Empty loadable segment detected, is this intentional ?

address@hidden linux-2.6.20-gujin]$
 My answer is that it is not needed to keep this empty loadable segment, you can
strip it.
 I do not care of the warning because that command is used "-O binary" by Linux
Makefile and does not produce the warning.


 Thanks,
 Etienne.

-- 
           Summary: problems with linker / strip / BFD
           Product: binutils
           Version: 2.17
            Status: NEW
          Severity: normal
          Priority: P2
         Component: binutils
        AssignedTo: unassigned at sources dot redhat dot com
        ReportedBy: etienne_lorrain at yahoo dot fr
                CC: bug-binutils at gnu dot org
 GCC build triplet: i386-redhat-linux
  GCC host triplet: i386-redhat-linux
GCC target triplet: i386-redhat-linux


http://sourceware.org/bugzilla/show_bug.cgi?id=4007

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