I've built a test ELF program using the LSB SDK (note that my question is not specific to LSB):
$ /opt/lsb/bin/lsbcc tst.c
$ ls -l a.out
-rwxr-xr-x 1 math math 10791 2009-10-13 20:13 a.out
$ file a.out
a.out: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.15, not stripped
But I am unable to launch it (yes, I assure you the file is in the directory...):
$ ./a.out
bash: ./a.out: No such file or directory
$ uname -a
Linux math 2.6.28-15-generic #52-Ubuntu SMP Wed Sep 9 10:48:52 UTC 2009 x86_64 GNU/Linux
I think there is an ELF dependency which is not fulfill but I don't know how to find it. Is there a tool similar to ldd for libraries which can be used to found the missing link?
I don't think it is related to the 2.6.15/2.6.28-15 difference because the LSB compiler is working:
$ file /opt/lsb/bin/lsbcc
/opt/lsb/bin/lsbcc: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.4, not stripped
Just in case, here is the ELF dynamic section of a.out:
0x0000000000000001 (NEEDED) Shared library: [libpthread.so.0]
0x0000000000000001 (NEEDED) Shared library: [libm.so.6]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000c (INIT) 0x400428
0x000000000000000d (FINI) 0x400638
0x0000000000000004 (HASH) 0x400278
0x0000000000000005 (STRTAB) 0x400350
0x0000000000000006 (SYMTAB) 0x4002a8
0x000000000000000a (STRSZ) 121 (bytes)
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000015 (DEBUG) 0x0
0x0000000000000003 (PLTGOT) 0x600fe8
0x0000000000000002 (PLTRELSZ) 24 (bytes)
0x0000000000000014 (PLTREL) RELA
0x0000000000000017 (JMPREL) 0x400410
0x0000000000000007 (RELA) 0x4003f8
0x0000000000000008 (RELASZ) 24 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x000000006ffffffe (VERNEED) 0x4003d8
0x000000006fffffff (VERNEEDNUM) 1
0x000000006ffffff0 (VERSYM) 0x4003ca
0x0000000000000000 (NULL) 0x0
This looks like what happens when the ELF interpreter is missing.
Ensure that /lib/ld-lsb.so.2 (or similar; varies by LSB version and architecture) exists. ldd and readelf -l will be able to show the ELF interpreter your executable is requesting.
(lsbcc (or something in the LSB toolchain) overrides the system's default /lib/ld-linux.so.2, probably by passing -Wl,--dynamic-linker=/lib/ld-lsb.so.2 to the compiler, for reasons I think are rather silly (Glibc has always provided fairly excellent backwards-compatibility here), but there you have it.)
Related
Here is a very simple assembly program, just return 12 after executed.
$ cat a.asm
global _start
section .text
_start: mov rax, 60 ; system call for exit
mov rdi, 12 ; exit code 12
syscall
It can be built and executed correctly:
$ nasm -f elf64 a.asm && ld a.o && ./a.out || echo $?
12
But the size of a.out is big, it is more than 4k:
$ wc -c a.out
4664 a.out
I try to understand it by reading elf content:
$ readelf -l a.out
Elf file type is EXEC (Executable file)
Entry point 0x401000
There are 2 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000000000 0x0000000000400000 0x0000000000400000
0x00000000000000b0 0x00000000000000b0 R 0x1000
LOAD 0x0000000000001000 0x0000000000401000 0x0000000000401000
0x000000000000000c 0x000000000000000c R E 0x1000
Section to Segment mapping:
Segment Sections...
00
01 .text
it is strange, segment 00 is aligned by 0x1000, I think it means such segment at least will occupy 4096 bytes.
My question is what is this segment 00?
(nasm version 2.14.02, ld version 2.34, os is Ubuntu 20.04.1)
Since it starts at file offset zero, it is probably a "padding" segment introduced to make the loading of the ELF more efficient.
The .text segment will, in fact, be already aligned in the file as it should be in memory.
You can force ld not to align sections both in memory and in the file with -n. You can also strip the symbols with -s.
This will reduce the size to about 352 bytes.
Now the ELF contains:
The ELF header (Needed)
The program header table (Needed)
The code (Needed)
The string table (Possibly unneeded)
The section table (Possibly unneeded)
The string table can be removed, but apparently strips can't do that.
I've removed the .shstrtab section data and all the section headers manually to shrink the size down to 144 bytes.
Consider that 64 bytes come from the ELF header, 60 from the single program header and 12 from your code; for a total of 136 bytes.
The extra 8 bytes are padding, 4 bytes at the end of the code section (easy to remove), and one at the end of the program header (which requires a bit of patching).
Consider this AMD64 assembly program:
.globl _start
_start:
xorl %edi, %edi
movl $60, %eax
syscall
If I compile that with gcc -nostdlib and run ldd a.out, I get this:
statically linked
If I instead compile that with gcc -static -nostdlib and run ldd a.out, I get this:
not a dynamic executable
What's the difference between statically linked and not a dynamic executable? And if my binary was already statically linked, why does adding -static affect anything?
There are two separate things here:
Requesting an ELF interpreter (ld.so) or not.
Like #!/bin/sh but for binaries, runs before your _start.
This is the difference between a static vs. dynamic executable.
The list of dynamically linked libraries for ld.so to load happens to be empty.
This is apparently what ldd calls "statically linked", i.e. that any libraries you might have linked at build time were static libraries.
Other tools like file and readelf give more information and use terminology that matches what you'd expect.
Your GCC is configured so -pie is the default, and gcc doesn't make a static-pie for the special case of no dynamic libraries.
gcc -nostdlib just makes a PIE that happens not to link to any libraries but is otherwise identical to a normal PIE, specifying an ELF interpreter.
ldd confusingly calls this "statically linked".
file : ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2 ...
gcc -nostdlib -static overrides the -pie default and makes a true static executable.
file : ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked ...
gcc -nostdlib -no-pie also chooses to make a static executable as an optimization for the case where there are no dynamic libraries at all. Since a non-PIE executable couldn't have been ASLRed anyway, this makes sense. Byte-for-byte identical to the -static case.
gcc -nostdlib -static-pie makes an ASLRable executable that doesn't need an ELF interpreter. GCC doesn't do this by default for gcc -pie -nostdlib, unlike the no-pie case where it chooses to sidestep ld.so when no dynamically-linked libraries are involved.
file : ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), statically linked ...
-static-pie is obscure, rarely used, and older file doesn't identify it as statically linked.
-nostdlib doesn't imply -no-pie or -static, and -static-pie has to be explicitly specified to get that.
gcc -static-pie invokes ld -static -pie, so ld has to know what that means. Unlike with the non-PIE case where you don't have to ask for a dynamic executable explicitly, you just get one if you pass ld any .so libraries. I think that's why you happen to get a static executable from gcc -nostdlib -no-pie - GCC doesn't have to do anything special, it's just ld doing that optimization.
But ld doesn't enable -static implicitly when -pie is specified, even when there are no shared libraries to link.
Details
Examples generated with gcc --version gcc (Arch Linux 9.3.0-1) 9.3.0
ld --version GNU ld (GNU Binutils) 2.34 (also readelf is binutils)
ldd --version ldd (GNU libc) 2.31
file --version file-5.38 - note that static-pie detection has changed in recent patches, with Ubuntu cherry-picking an unreleased patch. (Thanks #Joseph for the detective work) - this in 2019 detected dynamic = having a PT_INTERP to handle static-pie, but it was reverted to detect based on PT_DYNAMIC so shared libraries count as dynamic. debian bug #948269. static-pie is an obscure rarely-used feature.
GCC ends up running ld -pie exit.o with a dynamic linker path specified, and no libraries. (And a boatload of other options to support possible LTO link-time optimization, but the keys here are -dynamic-linker /lib64/ld-linux-x86-64.so.2 -pie. collect2 is just a wrapper around ld.)
$ gcc -nostdlib exit.s -v # output manually line wrapped with \ for readability
...
COLLECT_GCC_OPTIONS='-nostdlib' '-v' '-mtune=generic' '-march=x86-64'
/usr/lib/gcc/x86_64-pc-linux-gnu/9.3.0/collect2 \
-plugin /usr/lib/gcc/x86_64-pc-linux-gnu/9.3.0/liblto_plugin.so \
-plugin-opt=/usr/lib/gcc/x86_64-pc-linux-gnu/9.3.0/lto-wrapper \
-plugin-opt=-fresolution=/tmp/ccoNx1IR.res \
--build-id --eh-frame-hdr --hash-style=gnu \
-m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -pie \
-L/usr/lib/gcc/x86_64-pc-linux-gnu/9.3.0 \
-L/usr/lib/gcc/x86_64-pc-linux-gnu/9.3.0/../../../../lib -L/lib/../lib \
-L/usr/lib/../lib \
-L/usr/lib/gcc/x86_64-pc-linux-gnu/9.3.0/../../.. \
/tmp/cctm2fSS.o
You get a dynamic PIE with no dependencies on other libraries. Running it still invokes the "ELF interpreter" /lib64/ld-linux-x86-64.so.2 on it which runs before jumping to your _start. (Although the kernel has already mapped the executable's ELF segments to ASLRed virtual addresses, along with ld.so's text / data / bss).
file and readelf are more descriptive.
PIE non-static executable from gcc -nostdlib
$ gcc -nostdlib exit.s -o exit-default
$ ls -l exit-default
-rwxr-xr-x 1 peter peter 13536 May 2 02:15 exit-default
$ ldd exit-default
statically linked
$ file exit-default
exit-default: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=05a4d1bdbc94d6f91cca1c9c26314e1aa227a3a5, not stripped
$ readelf -a exit-default
...
Type: DYN (Shared object file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x1000
...
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
PHDR 0x0000000000000040 0x0000000000000040 0x0000000000000040
0x00000000000001f8 0x00000000000001f8 R 0x8
INTERP 0x0000000000000238 0x0000000000000238 0x0000000000000238
0x000000000000001c 0x000000000000001c R 0x1
[Requesting program interpreter: /lib64/ld-linux-x86-64.so.2]
LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x00000000000002b1 0x00000000000002b1 R 0x1000
LOAD 0x0000000000001000 0x0000000000001000 0x0000000000001000
0x0000000000000009 0x0000000000000009 R E 0x1000
... (the Read+Exec segment to be mapped at virt addr 0x1000 is where your text section was linked.)
If you strace it you can also see the differences:
$ gcc -nostdlib exit.s -o exit-default
$ strace ./exit-default
execve("./exit-default", ["./exit-default"], 0x7ffe1f526040 /* 51 vars */) = 0
brk(NULL) = 0x5617eb1e4000
arch_prctl(0x3001 /* ARCH_??? */, 0x7ffcea703380) = -1 EINVAL (Invalid argument)
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f9ff5b3e000
arch_prctl(ARCH_SET_FS, 0x7f9ff5b3ea80) = 0
mprotect(0x5617eabac000, 4096, PROT_READ) = 0
exit(0) = ?
+++ exited with 0 +++
vs. -static and -static-pie the first instruction executed in user-space is your _start (which you can also check with GDB using starti).
$ strace ./exit-static-pie
execve("./exit-static-pie", ["./exit-static-pie"], 0x7ffcdac96dd0 /* 51 vars */) = 0
exit(0) = ?
+++ exited with 0 +++
gcc -nostdlib -static-pie
$ gcc -nostdlib -static-pie exit.s -o exit-static-pie
$ ls -l exit-static-pie
-rwxr-xr-x 1 peter peter 13440 May 2 02:18 exit-static-pie
peter#volta:/tmp$ ldd exit-static-pie
statically linked
peter#volta:/tmp$ file exit-static-pie
exit-static-pie: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), statically linked, BuildID[sha1]=daeb4a8f11bec1bb1aaa13cd48d24b5795af638e, not stripped
$ readelf -a exit-static-pie
...
Type: DYN (Shared object file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x1000
...
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000229 0x0000000000000229 R 0x1000
LOAD 0x0000000000001000 0x0000000000001000 0x0000000000001000
0x0000000000000009 0x0000000000000009 R E 0x1000
... (no Interp header, but still a read+exec text segment)
Notice that the addresses are still relative to the image base, leaving ASLR up to the kernel.
Surprisingly, ldd doesn't say that it's not a dynamic executable. That might be a bug, or a side effect of some implementation detail.
gcc -nostdlib -static traditional non-PIE old-school static executable
$ gcc -nostdlib -static exit.s -o exit-static
$ ls -l exit-static
-rwxr-xr-x 1 peter peter 4744 May 2 02:26 exit-static
peter#volta:/tmp$ ldd exit-static
not a dynamic executable
peter#volta:/tmp$ file exit-static
exit-static: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, BuildID[sha1]=1b03e3d05709b7288fe3006b4696fd0c11fb1cb2, not stripped
peter#volta:/tmp$ readelf -a exit-static
ELF Header:
...
Type: EXEC (Executable file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x401000
... (Note the absolute entry-point address nailed down at link time)
(And that the ELF type is EXEC, not DYN)
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000000000 0x0000000000400000 0x0000000000400000
0x000000000000010c 0x000000000000010c R 0x1000
LOAD 0x0000000000001000 0x0000000000401000 0x0000000000401000
0x0000000000000009 0x0000000000000009 R E 0x1000
NOTE 0x00000000000000e8 0x00000000004000e8 0x00000000004000e8
0x0000000000000024 0x0000000000000024 R 0x4
Section to Segment mapping:
Segment Sections...
00 .note.gnu.build-id
01 .text
02 .note.gnu.build-id
...
Those are all the program headers; unlike pie / static-pie I'm not leaving any out, just other whole parts of the readelf -a output.
Also note the absolute virtual addresses in the program headers that don't give the kernel a choice where in virtual address space to map the file. This is the difference between EXEC and DYN types of ELF objects. PIE executables are shared objects with an entry point, allowing us to get ASLR for the main executable. Actual EXEC executables have a link-time-chosen memory layout.
ldd apparently only reports "not a dynamic executable" when both:
no ELF interpreter (dynamic linker) path
ELF type = EXEC
I am cross-compiling for an ARM embedded Linux platform running Ubuntu 15.04. Previous, statically-linked, versions of this program have run just fine. Recently I needed to link in libproprietary (lib name changed for this question), which is only available as an .so.
libproprietary.so works; I am able to run a different program that depends on it.
$ uname -a
Linux <hostname> 3.10.92-71 #1 SMP PREEMPT Fri Dec 18 00:38:54 BRST 2015 armv7l armv7l armv7l GNU/Linux
The problem:
$ ./myprogram
-bash: ./myprogram: No such file or directory
What I've tried:
$ ldd ./myprogram
libproprietary.so.2 => /usr/lib/libproprietary.so.2 (0xb6bbc000)
librt.so.1 => /lib/arm-linux-gnueabihf/librt.so.1 (0xb6ba6000)
libpthread.so.0 => /lib/arm-linux-gnueabihf/libpthread.so.0 (0xb6b92000)
libusb-1.0.so.0 => /lib/arm-linux-gnueabihf/libusb-1.0.so.0 (0xb6b72000)
libstdc++.so.6 => /usr/lib/arm-linux-gnueabihf/libstdc++.so.6 (0xb6ab8000)
libm.so.6 => /lib/arm-linux-gnueabihf/libm.so.6 (0xb6a43000)
libc.so.6 => /lib/arm-linux-gnueabihf/libc.so.6 (0xb6955000)
/usr/lib/ld.so.1 => /lib/ld-linux-armhf.so.3 (0xb6f28000)
libgcc_s.so.1 => /lib/arm-linux-gnueabihf/libgcc_s.so.1 (0xb692c000)
libudev.so.1 => /lib/arm-linux-gnueabihf/libudev.so.1 (0xb690f000)
$ file ./myprogram
./myprogram: ELF 32-bit LSB executable, ARM, EABI5 version 1 (GNU/Linux), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=881d76b2ce20f32aef95796b4fee9f01e492a7d2, not stripped
$ file /bin/ls
/bin/ls: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=a687c2baf9963c62c6abd209863d360dd0863686, stripped
$ readelf -l myprogram| grep interpreter
[Requesting program interpreter: /usr/lib/ld.so.1]
$ strace ./myprogram
execve("./myprogram", ["./myprogram"...], [/* 21 vars */]) = -1 ENOENT (No such file or directory)
write(2, "strace: exec: No such file or di"..., 40strace: exec: No such file or directory
) = 40
exit_group(1) = ?
+++ exited with 1 +++
$ ls -l myprogram
-rwxrwxr-x [details snipped]
$ file /usr/lib/libproprietary.so.<version>
/usr/lib/libproprietary.so.<version>: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, BuildID[sha1]=d9b4ba3b9ec03779792984bc8a89ceede5737455, stripped
It appears that the interpreter, /usr/lib/ld.so.1, does not exist. I'm going to guess that it should be similar to what /bin/ls is using:
$ readelf -l /bin/ls | grep interpreter
[Requesting program interpreter: /lib/ld-linux-armhf.so.3]
I don't know how to fix this in my link step however.
ccache arm-linux-gnueabihf-g++ -o myprogram -static -Wl,--whole-archive -lpthread -Wl,--no-whole-archive -Wl,-no-undefined -pthread -Wl,-Bdynamic -lproprietary -Wl,-rpath-link=result/debug/lib -Wl,-rpath=\$ORIGIN/../../../../result/debug/lib variant-dir/debug/core-.o -Lresult/debug/lib -Wl,-Bstatic -l<other libs>
I did try moving -Wl,-Bdynamic -lproprietary after the core-.o word, but that didn't change anything.
It appears that the interpreter, /usr/lib/ld.so.1, does not exist. I'm going to guess that it should be similar to what /bin/ls is using:
Correct. You could change the interpreter by adding -Wl,--dynamic-linker=/lib/ld-linux-armhf.so.3 flag at link time.
However,
Your toolchain may be targeting a different version of libc from the one you actually have installed (in which case the program will likely crash).
If it is targeting correct libc, then your toolchain is mis-configured.
This question already has an answer here:
Error during Cross-compiling C code with Dynamic libraries
(1 answer)
Closed 6 years ago.
I am using VAR-SOM-AM33 board and want to run sample code like hello world run on device and it gives -sh:./test:not found error
Toolchain used for compile code is gcc-linaro-arm-linux-gnueabihf-4.7-2013.03-20130313_linux.
Code is as below
#include <stdio.h>
int main(){
printf("hello world");
return 0;
}
for crosscompile file
arm-linux-gnueabihf-gcc test.c -march=armv7-a -marm -mthumb-interwork -mfloat-abi=hard -mfpu=neon -mtune=cortex-a8 -o test
output binary is shows as follows
test: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.31, BuildID[sha1]=2ce1c5b3d97dac2093fe2cd2d340cdaa9989923f, not stripped
After copy that file into hardware and run it shows following error
root#am335x-evm:~# ./test
-sh: ./test: not found
File permission also change by
root#am335x-evm:~# chmod +x test
but result shows same not found error.
Demo file which is running on hardware,its architecture as follows
root#am335x-evm:~# readelf -A /usr/bin/hello
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "7-A"
Tag_CPU_arch: v7
Tag_CPU_arch_profile: Application
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-2
Tag_VFP_arch: VFPv3
Tag_Advanced_SIMD_arch: NEONv1
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align8_needed: Yes
Tag_ABI_align8_preserved: Yes, except leaf SP
Tag_ABI_enum_size: int
Tag_ABI_HardFP_use: SP and DP
and file which is cross compiled,its architecture as follows
root#am335x-evm:~# readelf -A test
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "7-A"
Tag_CPU_arch: v7
Tag_CPU_arch_profile: Application
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-2
Tag_VFP_arch: VFPv3
Tag_Advanced_SIMD_arch: NEONv1
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align8_needed: Yes
Tag_ABI_align8_preserved: Yes, except leaf SP
Tag_ABI_enum_size: int
Tag_ABI_HardFP_use: SP and DP
Tag_ABI_VFP_args: VFP registers
Tag_CPU_unaligned_access: v6
Tag_unknown_44: 1 (0x1)
Also hardware cpuinfo is as follows
root#am335x-evm:~# cat /proc/cpuinfo
Processor : ARMv7 Processor rev 2 (v7l)
BogoMIPS : 718.02
Features : swp half thumb fastmult vfp edsp thumbee neon vfpv3 tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x3
CPU part : 0xc08
CPU revision : 2
Hardware : Variscite VAR-SOM-AM33
Revision : 0000
Serial : 0000000000000000
I have tried running ldd command on target device.
root#am335x-evm:~# ldd
-sh: ldd: not found
So I suspect that the issue is related to the linker.
If I simply compile the file, without linking it.
arm-linux-gnueabihf-gcc -mtune=cortex-a8 -march=armv7 -O -c test.c -o test
Now if I run this file I get this error.
root#am335x-evm:~# chmod +x test
root#am335x-evm:~# ./test
./test: line 1: syntax error: word unexpected (expecting ")")
please suggest how to resolve this.
Thanks for solution, I found error with linker.
existing file has linker ld-linux.so.3 and crosscompiled file has linker ld-linux-armhf.so.3
root#am335x-evm:/usr/bin# readelf -l hello
Elf file type is EXEC (Executable file)
Entry point 0x82fc
There are 8 program headers, starting at offset 52
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x00044c 0x0000844c 0x0000844c 0x00008 0x00008 R 0x4
PHDR 0x000034 0x00008034 0x00008034 0x00100 0x00100 R E 0x4
INTERP 0x000134 0x00008134 0x00008134 0x00013 0x00013 R 0x1
[Requesting program interpreter: /lib/ld-linux.so.3]
crosscompiled file program header
root#am335x-evm:~# readelf -l test
Elf file type is EXEC (Executable file)
Entry point 0x82f9
There are 8 program headers, starting at offset 52
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
EXIDX 0x000450 0x00008450 0x00008450 0x00008 0x00008 R 0x4
PHDR 0x000034 0x00008034 0x00008034 0x00100 0x00100 R E 0x4
INTERP 0x000134 0x00008134 0x00008134 0x00019 0x00019 R 0x1
[Requesting program interpreter: /lib/ld-linux-armhf.so.3]
after chang that linker program runs on target device.
root#am335x-evm:~# cd /lib/
root#am335x-evm:/lib# ls -l ld-linux.so.3
lrwxrwxrwx 1 1000 1000 12 Aug 7 2012 ld-linux.so.3 -> ld-2.12.2.so
root#am335x-evm:/lib# ln -s /li ld-2.12.2.so ld-linux-armhf.so.3
/lib/ /linuxrc
root#am335x-evm:/lib# ln -s /lib/ld-2.12.2.so ld-linux-armhf.so.3
root#am335x-evm:/lib# ldconfig
root#am335x-evm:/lib# cd
root#am335x-evm:~# ./test
hello worldroot#am335x-evm:~#
Here is a dump from a.out
STACK off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**2
filesz 0x00000000 memsz 0x00000000 flags rwx
Why does a stack segment have executable attribute?
Why isn't there a heap segment with rw- attribute?
//On ubuntu 32bit machine. Program is a simple hello world.
Command:
ld test.o startup.s; objdump -dhSxt -M intel-pneumonic a.out
//startup.s has a small assembly code with _start symbol which calls main and exits after main returns.
Command: gcc test.c
Try gcc test.c -Wl,-z,noexecstack.
That should be the default on any reasonably modern distribution.