Re: RFC: binutils PATCH: Set e_type to ET_EXEC for -pie -Ttext-segment=0xXXX

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Mon, Dec 9, 2013 at 7:23 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 12/09/2013 07:05 PM, H.J. Lu wrote:
>>>
>>> I see.  Maybe linker can set ET_EXEC if vaddr is non-zero.
>>>
>>
>> Linker sets e_type in ELF header to ET_DYN for -pie -Ttext-segment=0xXXX.
>> When I added -Ttext-segment=0xXXX, one goal was to load
>> small model executable above 4GB on Linux/x86-64, which
>> was done with -pie -Ttext-segment=0xXXX.  But -pie sets
>> e_type in ELF header to ET_DYN and kernel may ignore
>> p_vaddr in ELF header to load ET_DYN binary at a random
>> address.  This patch changes ld to set e_type in ELF header
>> to ET_EXEC if the first PT_LOAD segment has non-zero
>> p_vaddr.  If this is unacceptable as generic ELF change,
>> I can make it specific to x86.
>>
>
> Why not just drop the -pie from the command line?  I would expect -pie
> to set ET_DYN, but if you want to load at a specific address one would
> expect to use -Ttext-segment=... and *not* -pie.
>

No.  We must keep -pie.  Without -pie, we can't set -Ttext-segment=
to above 4GB:

[hjl@gnu-6 tmp]$ gcc  a.c -Wl,-Ttext-segment=0x7ff000000
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../lib64/crt1.o: In
function `_start':
(.text+0x12): relocation truncated to fit: R_X86_64_32S against symbol
`__libc_csu_fini' defined in .text section in
/usr/lib64/libc_nonshared.a(elf-init.oS)
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../lib64/crt1.o: In
function `_start':
(.text+0x19): relocation truncated to fit: R_X86_64_32S against symbol
`__libc_csu_init' defined in .text section in
/usr/lib64/libc_nonshared.a(elf-init.oS)
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../lib64/crt1.o: In
function `_start':
(.text+0x20): relocation truncated to fit: R_X86_64_32S against symbol
`main' defined in .text section in /tmp/ccV9AIMR.o
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/crtbegin.o: In function
`deregister_tm_clones':
crtstuff.c:(.text+0x1): relocation truncated to fit: R_X86_64_32
against symbol `__TMC_END__' defined in .data section in a.out
crtstuff.c:(.text+0x8): relocation truncated to fit: R_X86_64_32S
against `.tm_clone_table'
crtstuff.c:(.text+0x23): relocation truncated to fit: R_X86_64_32
against `.tm_clone_table'
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/crtbegin.o: In function
`register_tm_clones':
crtstuff.c:(.text+0x31): relocation truncated to fit: R_X86_64_32
against symbol `__TMC_END__' defined in .data section in a.out
crtstuff.c:(.text+0x38): relocation truncated to fit: R_X86_64_32S
against `.tm_clone_table'
crtstuff.c:(.text+0x63): relocation truncated to fit: R_X86_64_32
against `.tm_clone_table'
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/crtbegin.o: In function `frame_dummy':
crtstuff.c:(.text+0xa6): relocation truncated to fit: R_X86_64_32 against `.jcr'
/tmp/ccV9AIMR.o: In function `main':
a.c:(.text+0x5): additional relocation overflows omitted from the output
collect2: error: ld returned 1 exit status
[hjl@gnu-6 tmp]$ gcc -fpie -pie  a.c -Wl,-Ttext-segment=0x7ff000000
[hjl@gnu-6 tmp]$


---
H.J.