On Mon, May 20, 2019 at 2:57 PM Uros Bizjak <ubiz...@gmail.com> wrote: > > On Mon, May 20, 2019 at 6:12 PM tedheadster <tedheads...@gmail.com> wrote: > > Did you instead mean "zeroing %EBX and %ECX regs should be enough"? > > Ah, yes. This is what I meant to say. The patch clears %ebx and %ecx. >
Uros, your patch worked on real 32-bit hardware. The assembly output is nearly identical to mine, with merely a re-ordering when setting the %eax, %ebx, and %ecx registers. But of course your code does not compile into x86_64 systems (nice touch). test $0x200000,%eax je 0xb7e214c0 <rdrand+128> xor %edi,%edi <--- zero for use below mov %edi,%eax cpuid test %eax,%eax je 0xb7e214c0 <rdrand+128> mov $0x1,%eax mov %edi,%ebx <--- zero register mov %edi,%ecx <--- zero register cpuid If this is accepted upstream, can we please get it backported to some of the major releases: 8.2.0, 7.3.0, 6.4.0 and 5.4.0? - Matthew
