On Mon, 6 Jan 2025 at 17:13, David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote: > > On Mon, 2025-01-06 at 17:09 +0100, Ard Biesheuvel wrote: > > > > I suppose you're referring to > > > > #ifdef CONFIG_KEXEC_JUMP > > /* Saved in save_processor_state. */ > > movq $saved_context, %rax > > lgdt saved_context_gdt_desc(%rax) > > #endif > > > > Any reason not to simply use > > > > lgdt saved_context+saved_context_gdt_desc(%rip) > > > > here? > > Because the %rip isn't what you (and the linker) think it is. > > This code is copied into a control page which is allocated as part of > the kexec kimage. It can only access things within that same page via > %rip. (Which is not as much of a restriction as it sounds, as for most > of its execution the rest of the kernel isn't even present in the page > tables). Ah I was looking at an older version of that file - I now see that the preceding (%rip) references have been replaced as well. In any case, thanks for the head's up - I'll get back to this at some point and cc you if making any further changes here.
