Trouble with dynamic executables

[Andrew Duane]

I've figured out what the problem is. The elf header of a sample dynamic executable shows:
 
Elf file type is EXEC (Executable file)
Entry point 0x1200028f0
There are 7 program headers, starting at offset 64
 
Program Headers:
  Type           Offset             VirtAddr           PhysAddr           FileSiz            MemSiz              Flags  Align
  PHDR           0x0000000000000040 0x0000000120000040 0x0000000120000040 0x0000000000000188 0x0000000000000188  R E    8
  INTERP         0x0000000000012788 0x0000000120012788 0x0000000120012788 0x0000000000000015 0x0000000000000015  R      1
      [Requesting program interpreter: /libexec/ld-elf.so.1]
  LOAD           0x0000000000000000 0x0000000120000000 0x0000000120000000 0x00000000000127bc 0x00000000000127bc  R E    10000
  LOAD           0x0000000000013000 0x0000000120023000 0x0000000120023000 0x00000000000017d8 0x0000000000003c28  RW     10000
  DYNAMIC        0x0000000000000808 0x0000000120000808 0x0000000120000808 0x00000000000001e0 0x00000000000001e0  RWE    8
  NOTE           0x00000000000127a4 0x00000001200127a4 0x00000001200127a4 0x0000000000000018 0x0000000000000018  R      4
  NULL           0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000         8

Note section 1 the INTERP header: the offset is 0x12788. There's a check in the ELF64 image activator to see if the offset is outside the first page and returns ENOEXEC. The exec path reads in the first page first, and tries to figure out what to do with the rest. So if the interpreter name isn't in the first page, it can't decode it.

This is a toolchain issue, or some setup issue.
 
/Andrew
 
 

________________________________

From: bhanuprakash bodireddy [mailto:bhanuprakashbodireddy at gmail.com] 
Sent: Thursday, April 14, 2011 3:11 PM
To: Andrew Duane
Cc: mips at freebsd.org
Subject: Re: Trouble with dynamic executables


I had a similar issue the other day when i did a fresh build world. I tried it to reproduce the issue you reported and its pretty much there in the trunk.
But the last buildworld has no such issues and am still using the same old fs image to boot on to the octeon boards. 

I believe, some recent fixes should have caused this. 

Thanks,
Bhanu Prakash.


On Thu, Apr 14, 2011 at 11:01 AM, Andrew Duane <aduane at juniper.net> wrote:


	I've pretty much completed my board bringup of an OCTEON based board, but am still battling one *major* issue. Dynamically linked executables do not work at all. Any time I try to run one, I get "Exec format error" (ENOEXEC). Sample output from file is:
	
	Statically linked /bin/cat:
	
	bin/cat:      ELF 64-bit MSB executable, MIPS, MIPS64 rel2 version 1 (FreeBSD), for FreeBSD 9.0 (900035), statically linked, FreeBSD-style, not stripped
	
	Dynamically linked /usr/bin/size:
	
	usr/bin/size: ELF 64-bit MSB executable, MIPS, MIPS64 rel2 version 1 (FreeBSD), for FreeBSD 9.0 (900035), dynamically linked (uses shared libs), FreeBSD-style, not stripped
	
	For now, I've sort of worked around this by editing close to 1000 Makefiles and making almost everything static. There must be a reason for this though. I've done a fresh update and rebuilt everything including the toolchain. Is there something missing from my system? The loader itself? Libraries? An ldscript file?
	
	--
	
	Andrew Duane             Juniper Networks
	978-589-0551             10 Technology Park Dr
	aduane at juniper.net       Westford, MA  01886-3418
	
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