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Re: [Xen-devel] [PATCH 05/17] xen/arm64: head: Introduce print_reg
On 7/15/19 7:46 PM, Volodymyr Babchuk wrote:
Hi Julien,
Hi,
Julien Grall writes:
At the moment, the user should save x30/lr if it cares about it.
Follow-up patches will introduce more use of putn in place where lr
should be preserved.
Furthermore, any user of putn should also move the value to register x0
if it was stored in a different register.
For convenience, a new macro is introduced to print a given register.
The macro will take care for us to move the value to x0 and also
preserve lr.
Lastly the new macro is used to replace all the callsite of putn. This
will simplify rework/review later on.
Note that CurrentEL is now stored in x5 instead of x4 because the latter
will be clobbered by the macro print_reg.
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
xen/arch/arm/arm64/head.S | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 84e26582c4..9142b4a774 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -90,8 +90,25 @@
bl puts ; \
mov lr, x3 ; \
RODATA_STR(98, _s)
+
+/*
+ * Macro to print the value of register \xb
+ *
+ * Clobbers x0 - x4
+ */
Despite its name, this macro can't print x4. I would recommend adding at
least comment about this. Static assertion would be even better, but
looks like we don't have them for asm code.
I have a new version of the function allowing to print x4. It is
basically just swapping "mov x4, lr" with "mov x0, \xb".
+.macro print_reg xb
+ mov x4, lr
+ mov x0, \xb
+ bl putn
+ mov lr, x4
+.endm
+
#else /* CONFIG_EARLY_PRINTK */
#define PRINT(s)
Cheers,
--
Julien Grall
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