32-bit programs generated by GCC-7.5.0 on ubuntu 18.04 are not based at 0x8048000


I write a very simple program

int main() {
        return 0;

and compile it into a 32-bit executable.

gcc main.c -m32 -o main

And then I check its base address with readelf -l main

root@acesrc:~# readelf -l main

Elf file type is DYN (Shared object file)
Entry point 0x3b0
There are 9 program headers, starting at offset 52

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  PHDR           0x000034 0x00000034 0x00000034 0x00120 0x00120 R   0x4
  INTERP         0x000154 0x00000154 0x00000154 0x00013 0x00013 R   0x1
      [Requesting program interpreter: /lib/ld-linux.so.2]
  LOAD           0x000000 0x00000000 0x00000000 0x006b4 0x006b4 R E 0x1000
  LOAD           0x000edc 0x00001edc 0x00001edc 0x0012c 0x00130 RW  0x1000
  DYNAMIC        0x000ee4 0x00001ee4 0x00001ee4 0x000f8 0x000f8 RW  0x4
  NOTE           0x000168 0x00000168 0x00000168 0x00044 0x00044 R   0x4
  GNU_EH_FRAME   0x000590 0x00000590 0x00000590 0x0003c 0x0003c R   0x4
  GNU_STACK      0x000000 0x00000000 0x00000000 0x00000 0x00000 RW  0x10
  GNU_RELRO      0x000edc 0x00001edc 0x00001edc 0x00124 0x00124 R   0x1

It shows that the entry point is 0x3b0, instead of something like 0x8048xxx. I have also tested it on SUSE, the programs are based at 0x8048000. What's the reason for that?

Ubuntu Version:

root@acesrc:~# uname -a
Linux acesrc 4.15.0-45-generic #48-Ubuntu SMP Tue Jan 29 16:28:13 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

GCC Version:

root@acesrc:~# gcc -v
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 7.5.0-3ubuntu1~18.04' --with-bugurl=file:///usr/share/doc/gcc-7/README.Bugs --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++ --prefix=/usr --with-gcc-major-version-only --program-suffix=-7 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie --with-system-zlib --with-target-system-zlib --enable-objc-gc=auto --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)
asked on Stack Overflow Feb 4, 2021 by Acesrc • edited Feb 4, 2021 by phuclv

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