打开后Galaxy S4改变UID / RFID(Galaxy S4 changing UID / RFID after turning on)

 对于pi2和pi3，我的代码退出了hyp模式（假设sd卡上没有config.txt）： 
 
mrs r0,cpsr
bic r0,r0,#0x1F
orr r0,r0,#0x13
msr spsr_cxsf,r0
add r0,pc,#4
msr ELR_hyp,r0
eret
 
 在树莓派网站上的baremetal论坛上有很多人，这个主题有不同的变化。 与旧时代不同，你不能在HYP模式下改变cpsr一次，但是如果你看一下eret指令它会接受一个新的cpsr以及分支（取一个新的lr来提供给电脑）并不是真正的回报而是改变cpsr的方法。 这就是我所知道的裸金属家伙正在做的事情。 
 
 当然，这里需要进行这些工作，并且它们恰好与pi一起工作。 
 
 如果你有一个config.txt，那么你需要小心一点，GPU为手臂“放置”核心的引导代码，让核心0通过，并将所有这些代码置于HYP模式。 （pi2和pi3），如果你选择打败那个： 
 
kernel_old=1
disable_commandline_tags=1
 
 然后由你来排序核心 
 
    mrs x0,mpidr_el1
    mov x1,#0xC1000000
    bic x1,x0,x1
    cbz x1,zero
not_zero:
    wfi
    b not_zero
zero:
 
 所以你没有让他们四个人几乎并行运行相同的代码...... 

My code to get out of hyp mode (assume no config.txt on the sd card) for both the pi2 and the pi3:
 
mrs r0,cpsr
bic r0,r0,#0x1F
orr r0,r0,#0x13
msr spsr_cxsf,r0
add r0,pc,#4
msr ELR_hyp,r0
eret
 
Lots of folks at the baremetal forum on the raspberry pi site, and there are variations on this theme. Unlike the good old days you cant just change the cpsr once in HYP mode, but if you look at the eret instruction it accepts a new cpsr as well as branching (takes a new lr to feed to the pc) not really a return but a way to change the cpsr. This is how the baremetal folks I know about are doing it.
 
There are of course assuptions required here to make this work and they happen to work with the pi.
 
If you have a config.txt then you need to be a little careful, the bootstrap code the GPU places for the arm "sorts" the cores and lets core 0 through as well as putting all of them in HYP mode. (both pi2 and pi3), if you choose to defeat that:
 
kernel_old=1
disable_commandline_tags=1
 
then it is up to you to sort the cores
 
    mrs x0,mpidr_el1
    mov x1,#0xC1000000
    bic x1,x0,x1
    cbz x1,zero
not_zero:
    wfi
    b not_zero
zero:
 
so you dont have all four of them running the same code almost in parallel...