Vào T2, ngày 19, 08 năm 2013 lúc 11:27 +0200, Paolo Bonzini viết:
> > The disassembled code is
> >
> > 0x1dd10: push %rbx
> > 0x1dd11: mov $0x6e,%eax
> > 0x1dd16: mov %rdi,%rbx
> > 0x1dd19: sub $0x20,%rsp
> > 0x1dd1d: test %rdi,%rdi
> > 0x1dd20: je 0xb1dd92
> > 0x1dd22: mov 0x4bf1e0(%rip),%eax
> > 0x1dd28: cmp $0xffffffff,%eax
> > 0x1dd2b: je 0xb1ddd0
> > 0x1dd31: test %eax,%eax
> > 0x1dd33: jne 0xb1dd92
> > 0x1dd35: mov 0xe1f55c(%rip),%rax
> > 0x1dd3c: cmpq $0x0,0xf0(%rax)
> > 0x1dd44: fildll 0xf0(%rax)
> > 0x1dd4a: js 0xb1ddf0
> > 0x1dd50: mov 0xe1f54a(%rip),%eax
> > 0x1dd56: mov %rax,-0x80(%rsp)
> > 0x1dd5b: fildll -0x80(%rsp)
> > 0x1dd5f: fmulp %st,%st(1)
> >
> > Not sure if it helps but rax after 0xb1dd35 contains the pointer to
> > mmap'd memory of /dev/hpet
>
> I think this wouldn't work even with the latest kernel. Emulation of
> x87 instructions is not supported yet.
I'm confused. How could this program work? It produces similar assembly
listing
-- 8< --
#include <stdio.h>
#include <stdint.h>
uint64_t s_rtcClockPeriod = 10;
uint64_t mc = 3000000000;
int main(int ac, char **av)
{
uint64_t value = (uint64_t)((long double)mc *
(long double)s_rtcClockPeriod /
1000000000.0L);
printf("%lu\n", value);
return 0;
}
-- 8< --
and the assembly I got is
-- 8< --
sub $0x18,%rsp
cmpq $0x0,0x200adc(%rip)
fildll 0x200ad6(%rip)
js 0x4005f8 <main+184>
cmpq $0x0,0x200ac0(%rip)
fildll 0x200aba(%rip)
js 0x400612 <main+210>
fmulp %st,%st(1)
fdivs 0x1ac(%rip)
flds 0x1aa(%rip)
fxch %st(1)
fucomi %st(1),%st
jae 0x4005c0 <main+128>
fstp %st(1)
fnstcw 0x16(%rsp)
...
-- 8< --
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