Hey I am the author of the blogpost. I have been reversing for a couple of years.
Usually, GDB just parses the ELF header to get the entry point. $ info file; in gdb should give you entrypoint of the binary almost always. In this case however the program has a corrupted section header, due to which gdb is not able to recognize the entry point. I dont exactly know which bytes in the header was corrupted, but apparently radare2 is able to get the entrypoint without much work. Should be fun to investigate more.
Usually, GDB just parses the ELF header to get the entry point. $ info file; in gdb should give you entrypoint of the binary almost always. In this case however the program has a corrupted section header, due to which gdb is not able to recognize the entry point. I dont exactly know which bytes in the header was corrupted, but apparently radare2 is able to get the entrypoint without much work. Should be fun to investigate more.