GDB examine memory permissions

Question

I've an address in memory and I want to find out the permissions (r/w/x) of that memory address.

E.g.

char *s = "hello";

Here, the string literal "hello" is stored in read-only memory. When running the program through gdb, is there a possibility to check out the permissions for that memory address (whether only read is permitted or etc) ?

Answer 1

You can first find where s is pointing to:

(gdb) print s
$6 = 0x400dbc "foo"

and then find the section in which it's in:

(gdb) maintenance info sections
Exec file:
    `/home/mfukar/tmp', file type elf64-x86-64.
    ...sections...
    0x00400db8->0x00400dfb at 0x00000db8: .rodata ALLOC LOAD READONLY DATA HAS_CONTENTS
    ...more sections...

and look for the READONLY flag.

Alternatively, look into /proc/PID/maps where PID is the pid of the process you're debugging and you can get with info proc.