Dne 01. 03. 25 v 23:48 Rudolf Marek napsal(a):
I don't know how slow is to do the jump back via far jump.
I did some micro benchmark on Raptorlake platform using other operating system
I'm very familiar with.
I added following sequence to the SYSCALL64 entrypoint:
.balign 16
sysc
Hi Andrew,
Dne 27. 02. 25 v 1:41 Andrew Cooper napsal(a):
For SYSCALL/SYSENTER it's a little more complicated. I think you want
to move the selectors so they don't alias __KERN_CS directly, so you can
then move back to __KERN_CS in a similar way
Yes I thought the CHECK_CS could be right befor
Hi Andrew,
Dne 25. 02. 25 v 22:14 Andrew Cooper napsal(a):
As stand-in for "the reader", I'll point out that you need to add #DB to
that list or you're in for a rude surprise when running the x86 selftests.
Thanks for pointing this out. I forgot about the interrupt shadow on SYSCALL
and possib
Hi Andrew,
Dne 25. 02. 25 v 19:10 Andrew Cooper napsal(a):
Very cunning. Yes it does, but the state needs to be safe to IRET back
to, and ...
... And intellectually very pleasing!
Would it work to have KERNEL_CS as last entry in the GDT table?
Therefore executing SYSCALL would set the CS as
Hi,
Dne 13. 02. 25 v 3:42 Andrew Cooper napsal(a):
The SYSCALL behaviour TLDR is:
%rcx = %rip
%r11 = %eflags
%cs = fixed attr
%ss = fixed attr
%rip = MSR_LSTAR
which means that %rcx (old rip) is the only piece of state which
userspace can't feasibly forge (and therefor
