> Date: Tue, 25 Jul 2023 16:51:18 +0200 > From: Christian Weisgerber <na...@mips.inka.de> > > Christian Weisgerber: > > > Because amd64 should suffer from the same problem: > > > > fr->cpu_opts.the_dct36 = dct36_avx; > > ... > > fr->cpu_opts.the_dct36 = dct36_x86_64; > > > > dct36_avx and dct36_x86_64 are assembly routines that lack the > > endbr64 landing pad. And yet, on my IBT-enabled amd64 laptop, > > mpg123 plays just fine with both the avx and x86_64 decoders. > > I have examined the generated assembly on the calling side. There > is no "jmp *%r11" or such. Instead, calling the function pointer > goes through __llvm_retpoline_r11: > > 0000000000000000 <__llvm_retpoline_r11>: > 0: e8 0b 00 00 00 callq 10 <__llvm_retpoline_r11+0x10> > 5: f3 90 pause > 7: 0f ae e8 lfence %eax > a: e9 f6 ff ff ff jmpq 5 <__llvm_retpoline_r11+0x5> > f: cc int3 > 10: 4c 89 1c 24 mov %r11,(%rsp) > 14: c3 retq > 15: 0f ae e8 lfence %eax
Thanks! That means that retpolines explain why you're not seeing any crashes.
