On Mon, 2024-12-16 at 12:09 +0000, David Woodhouse wrote: > On Sun, 2024-12-15 at 22:49 -0700, Nathan Chancellor wrote: > > On Sun, Dec 15, 2024 at 10:09:57AM +0000, David Woodhouse wrote: > > > On Sat, 2024-12-14 at 16:08 -0700, Nathan Chancellor wrote: > > > > > > > > I guess this seems somewhat unavoidable because control_page is just a > > > > 'void *', perhaps machine_kexec() should just be marked as __nocfi? This > > > > diff resolves that issue for me. > > > > > > The patch below seems to work too. I already wanted to deal with the > > > > Can confirm, thanks for the quick fix. With your fix for the first issue > > I reported, the fix I sent for LTO, and this patch below, I can kexec on > > a CFI and LTO enabled kernel without any issues. > > Argh, using SYM_TYPED_FUNC_START() leads to objtool having more opinions. > > I have the Clang build working in my tree now, but the GCC build now complains > > vmlinux.o: warning: objtool: relocate_kernel+0x0: unreachable instruction > > It seems like adding UNWIND_HINT_FUNC ought to be the answer for that? > But then it complains about this instead: > > vmlinux.o: warning: objtool: relocate_kernel+0x69: unsupported stack register modification > > That's the lea instruction at > lea PAGE_SIZE(%rsi), %rsp > 79: 48 8d a6 00 10 00 00 lea 0x1000(%rsi),%rsp > > I've pushed what I have to my kexec-debug branch; I was hoping to post > the fixes for the tip/x86/boot branch this morning but I've run out of > time and will be travelling for the rest of the week. Will try to get > something sent out this evening when I land. > > I may resort to the __nocfi option for now. As noted on the typedef > patch and in IRC, the whole SYM_TYPED_FUNC_START() thing using the type > information from the *C* code which is actually doing the call anyway, > is a bit tautological anyway. I've dropped this for now and just posted the __nocfi thing as the regression fix. I think we *should* provide the CFI information in relocate_kernel_64.S though, so I've left these commits in my tree at https://git.infradead.org/?p=users/dwmw2/linux.git;a=shortlog;h=refs/heads/kexec-debug I'd really appreciate some help in getting objtool to stop whining about them, for *both* Clang and GCC builds at the same time :)
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