How to disable relro while compilation?

Question

My doubt is how to compile the binary without RELRO? and why it is enabling FULL-RELRO when we are not providing any flags?

This is the code.

#include <stdio.h>
#include <stdlib.h>

int main(int argc, int *argv[])
{
    size_t *p = (size_t *) strtol(argv[1], NULL, 16);
    p[0] = 0xDEADBEEF;
    printf("RELRO: %p\n", p);
    return 0;
}

While compiling the above code with the parameters:

$ gcc -g -Wl,-z,relro -o test test.c

And running the checksec on the generated binary:

RELRO           STACK CANARY      NX            PIE             RPATH      RUNPATH  Symbols     FORTIFY Fortified   Fortifiable  FILE
Partial RELRO   No canary found   NX enabled    No PIE          No RPATH   No RUNPATH   69 Symbols     No   0       1   test

Compiling with the following command:

$ gcc -g -Wl,-z,relro,-z,now -o test test.c

And running the checksec on generated binary:

RELRO           STACK CANARY      NX            PIE             RPATH      RUNPATH  Symbols     FORTIFY Fortified   Fortifiable  FILE
Full RELRO      No canary found   NX enabled    PIE enabled     No RPATH   No RUNPATH   71 Symbols     No   0       1   test-full

While compiling with the command:

$ gcc -o test test.c

And running the checksec on the generated binary:

RELRO           STACK CANARY      NX            PIE             RPATH      RUNPATH  Symbols     FORTIFY Fortified   Fortifiable  FILE
Full RELRO      No canary found   NX enabled    PIE enabled     No RPATH   No RUNPATH   66 Symbols     No   0       1   test

Answer 1

To enable full relro:

-Wl, -z,relro,-z,now

What does this do? - it provides -z,relro,-z,now flag to linker as an argument. This enables full relro (notice -z,now flag).

Partial relro is enabled by default on modern gcc compilers.

How to disable relro? Pass following flag

-Wl,-z,norelro

Difference between full and partial relro: partial relro makes partial .got section (non .plt) section read-only and changes the alignment order sections making .got section appear before and data sections (.bss, '.data') and makes , while full relro makes complete .got section read-only (including .got.plt) and also reorders sections like in partial relro (incurring startup overhead).