如何阅读寄存器:RAX,RBX,RCX,RDX,RSP。 RBP,RSI,RDI在C或C ++? [英] How to read registers: RAX, RBX, RCX, RDX, RSP. RBP, RSI, RDI in C or C++?
问题描述
可以说,我想从这些寄存器(和pretty全部完蛋了)双核x64 CPU读取值。我怎样才能做到这一点?我可以简单的写是这样的:
Lets say I want to read values from those registers (and pretty all thats it) on dual core x64 CPU. How can I do this? Can I simply write something like:
uint64_t rax = 0, rbx = 0;
__asm__ __volatile__ (
/* read value from rbx into rbx */
"movq %%rdx, %0;\n"
/* read value from rax into rax*/
"movq %%rax, %1;\n"
/* output args */
: "=r" (rbx), "=r" (rax)
: /* no input */
/* clear both rdx and rax */
: "%rdx", "%rax"
);
然后只需打印出 RAX
和 RBX
?干杯
推荐答案
用gcc来做到这一点,正确的方法是用寄存器约束上:
The right way to do this with gcc is with register contraints:
uint64_t rax = 0, rbx = 0;
__asm__("" : "=a"(rax), "=b"(rbx) ::); /* make rax and rbx take on the current values in those registers */
请注意,你不需要任何实际的指示 - 约束告诉GCC下,什么都不做,该值RAX将在RAX和RBX的价值将在RBX
Note that you don't need any actual instructions -- the constraints tell gcc that after doing nothing, the value rax will be in rax and the value of rbx will be in rbx.
您可以使用约束 A
, B
, C
, D
,取值
和 D
(中后两者是RSI%和%RDI)。您还可以使用 YZ
为%XMM0。不幸的是,似乎没有对其他特定寄存器约束
You can use the constraints a
, b
, c
, d
, S
, and D
(the latter two are for %rsi and %rdi). You can also use Yz
for %xmm0. Unfortunately, there don't seem to be constraints for other specific registers.
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