Re: [Xen-devel] [PATCH] xen/arm64: Make sure we get all debug output

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Thu, 2016-02-04 at 17:49 +0100, Dirk Behme wrote:
> From: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
> 
> Starting in the wrong ELx mode I get the following debug output:
> 
> ...
> - Current EL 00000004 -
> - Xen must be entered in NS EL2 mode -
> - Boot failed -
> 
> The output of "Please update the bootloader" is missing here.
> 
> Make sure this is output, too. With this, we get
> 
> ...
> - Current EL 00000004 -
> - Xen must be entered in NS EL2 mode -
> - Please update the bootloader -
> - Boot failed -
> 
> as intended.

Ah, this is because gas does not concatenate strings in the same way as C,
i.e. in C:
        "A" "B" "C"

becomes 'A', 'B', 'C', '\0'

while in gas it becomes 'A', '\0', 'B', '\0', 'C', '\0'

I'd like to modify the "...is missing here" above to go a bit further:

    ...is missing here, because string concatenation in gas, unlike in C,
    keeps the \0 between each individual string.

Would that be OK with you? (I can do it on commit if you are happy with it)

> 
> Signed-off-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
> ---
> Âxen/arch/arm/arm64/head.S |ÂÂÂÂ4 ++--
> Â1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
> index 9ed9a93..19fa2bb 100644
> --- a/xen/arch/arm/arm64/head.S
> +++ b/xen/arch/arm/arm64/head.S
> @@ -309,8 +309,8 @@ common_start:
> ÂÂÂÂÂÂÂÂÂb.eqÂÂel2 /* Yes */
> Â
> ÂÂÂÂÂÂÂÂÂ/* OK, we're boned. */
> -ÂÂÂÂÂÂÂÂPRINT("- Xen must be entered in NS EL2 mode -\r\n" \
> -ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ"- Please update the bootloader -\r\n")
> +ÂÂÂÂÂÂÂÂPRINT("- Xen must be entered in NS EL2 mode -\r\n")
> +ÂÂÂÂÂÂÂÂPRINT("- Please update the bootloader -\r\n")
> ÂÂÂÂÂÂÂÂÂb fail
> Â
> Âel2:ÂÂÂÂPRINT("- Xen starting at EL2 -\r\n")

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