[PATCH v19 03/13] arm64/kexec: Add core kexec support

Hi,

On Mon, 2016-06-20 at 16:36 +0100, James Morse wrote:

+> 	> 	> switch (flag) {

quoted

+> > 	> > 	> > case IND_INDIRECTION:
+> > 	> > 	> > 	> > /* Set entry point just before the new list page. */
+> > 	> > 	> > 	> > entry = (kimage_entry_t *)addr - 1;

Ah, after this restructuring we end up cleaning this page as we fall-through,
and one kimage_entry_t at a time as we walk the list.

	> 	> 	> break;
?

I added this in, but that missing break shouldn't cause any problems.

quoted

+> > 	> > 	> > case IND_SOURCE:
+> > 	> > 	> > 	> > __flush_dcache_area(addr, PAGE_SIZE);
+> > 	> > 	> > 	> > break;
+> > 	> > 	> > case IND_DESTINATION:
+> > 	> > 	> > 	> > break;
+> > 	> > 	> > default:
+> > 	> > 	> > 	> > BUG();
+> > 	> > 	> > }
+> > 	> > }
+}

quoted

diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
new file mode 100644
index 0000000..51b73cd
--- /dev/null
+++ b/arch/arm64/kernel/relocate_kernel.S

[ ... ]

quoted

+.ltorg
+
+.align 3> > 	> > /* To keep the 64-bit values below naturally aligned. */
+
+.Lcopy_end:
+.org> > 	> > KEXEC_CONTROL_PAGE_SIZE

On 16/06/16 23:41, Geoff Levand wrote:

quoted

This is to check if arm64_relocate_new_kernel gets too
big.  The assembler should give an error if the location
counter is set backwards.

Cunning. (probably worth a comment).

I thought this was the standard way to do it...

This looks like it is need because we hard-coded KEXEC_CONTROL_PAGE_SIZE in
kexec.h, so the code must be smaller than that size.
It looks like this value is only ever passed to get_order(), could we just pass
the actual size? It shouldn't matter if it grows >4K, as the core code will
allocate enough memory, and the memcpy() in machine_kexec() uses the size too.

I thought 4K would be enough, but if some debugging code is
added it could get too big.

Reviewed-by: James Morse <james.morse@arm.com>

Thanks for your comments.

-Geoff