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
--
Christian "naddy" Weisgerber naddy@mips.inka.de
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