On Mon, May 16, 2022 at 11:07:43AM +0200, Alexander Gordeev wrote:
Yes, indeed. However implementing this without another register willdiff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.SIsn't the machine check handler refers to this memory before checking
index a6b45eaa3450..f2f30bfba1e9 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -172,9 +172,19 @@ _LPP_OFFSET = __LC_LPP
lgr %r14,\reg
larl %r13,\start
slgr %r14,%r13
- lghi %r13,\end - \start
- clgr %r14,%r13
+#ifdef CONFIG_AS_IS_LLVM
+ clgfrl %r14,.Lrange_size\@
+#else
+ clgfi %r14,\end - \start
+#endif
jhe \outside_label
+#ifdef CONFIG_CC_IS_CLANG
+ .section .rodata, "a"
+ .align 4
+.Lrange_size\@:
+ .long \end - \start
unrecoverable storage errors (with CHKSTG macro) as result of this change?
be quite of a challenge. So what I would prefer in any case: just
assume that this minimal set of memory accesses work. Actually I'd
seriously like to go a bit further, and even move the checks for
storage errors back to C for two reasons:
- this would make the machine check handler entry code easier again
- it would also allow to enter the machine check handler with DAT on
After all we rely anyway on the fact that at least the local lowcore +
the page(s) which contain text are still accessible. Assuming that a
couple of page tables also work won't make this much worse, but the
code much easier.
So I'd suggest: leave this code as is, and at some later point move
"rework" the early machine check handler code.
What do you think?