Hoi Ard,

On Tue, Oct 3, 2017 at 3:15 PM, Ard Biesheuvel
[off-list ref] wrote:

On 3 October 2017 at 13:41, Geert Uytterhoeven [off-list ref] wrote:

quoted

On Wed, Aug 30, 2017 at 4:55 AM, Nicolas Pitre [off-list ref] wrote:

quoted

Let's use optimized routines such as memcpy to copy .data and memzero
to clear .bss in the startup code instead of doing it one word at a
time. Those routines don't use any global data so they're safe to use
even if .data and .bss segments are not initialized.

In the .data copy case a temporary stack is installed in the .bss area
as the actual kernel stack is located within the copied data area. The
XIP kernel linker script ensures a 8 byte alignment for that purpose.

Finally, make the .data copy and related pointers surrounded by
CONFIG_XIP_KERNEL to make it obvious what it is all about. This will
allow for further cleanups in the non-XIP linker script.

Signed-off-by: Nicolas Pitre <redacted>
Reviewed-by: Ard Biesheuvel <redacted>

This is now commit 9520b1a1b5f7a348 ("ARM: head-common.S: speed up startup
code") in arm/for-next.

If CONFIG_DEBUG_LOCK_ALLOC=y, the kernel log is spammed with a few hundred
identical messages on various Renesas systems:

    unwind: Unknown symbol address c0800300
    unwind: Index not found c0800300

I've bisected this to the aforementioned commit.

c0800300 points to the instruction just after the __memzero call, cfr. below.

Do you have a clue? Thanks!

It looks like this patch results in start_kernel() being entered with
a different value for lr than before. Could you please try setting it
to zero instead, right before the jump to start_kernel() ?

I don't think the patch itself is to blame here, it simply triggers an
existing issue in the unwinder (if my analysis is correct, of course)

Your analysis looks correct to me, thanks! Patch sent.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds