Timeline for Robbers: Smallest subset of characters required for Turing Completeness
Current License: CC BY-SA 4.0
7 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| May 20, 2022 at 13:34 | comment | added | Peter Cordes | For modern GCC/ld/kernel, one way that works is to add __attribute__((section(".text"))) to the source before the array. as outputs "Warning: ignoring changed section attributes for .text", probably because GCC used a .section .text directive without the usual attributes that make it executable. Since as ignores it, we end up with this symbol in an executable .text section, with your custom machine code, so that Just Works without -zexecstack. It also works with tcc, with no warning; it seems it supports that attribute. | |
| May 20, 2022 at 13:20 | comment | added | Peter Cordes | This doesn't work on newer Linux systems. More modern Linux kernels only apply -zexecstack to the actual stack, instead of having it set the READ_IMPLIES_EXEC process personality. See How to get c code to execute hex machine code?. (The reason it used to not require -zexecstack is that older ld versions linked the .rodata section into the same ELF segment as .text. Newer ld avoids that, to minimize Spectre / ROP gadget surface area by not having any bytes in executable pages that don't need to be.) | |
| May 20, 2022 at 4:42 | comment | added | Qaziquza | Incredible crack! I shall do that. I thought that I had ruled out this solution with the { character, but I forgot about string literals! | |
| May 20, 2022 at 4:27 | history | edited | ais523 | CC BY-SA 4.0 | TIO link |
| May 20, 2022 at 4:19 | comment | added | ais523 | As I'm intentionally avoiding reputation, I don't have the reputation to mark the cop as cracked. Could someone do that for me? | |
| S May 20, 2022 at 4:17 | history | answered | ais523 | CC BY-SA 4.0 | |
| S May 20, 2022 at 4:17 | history | made wiki | Post Made Community Wiki by ais523 |