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Re: [PATCH 2/7] xen/arm32: head.S: Introduce a macro to load the physical address of a symbol





On 27/06/2022 07:31, Michal Orzel wrote:
Hi Julien,

Hi Michal,

On 24.06.2022 11:11, Julien Grall wrote:
From: Julien Grall <jgrall@xxxxxxxxxx>

A lot of places in the ARM32 assembly requires to load the physical address
of a symbol. Rather than open-coding the translation, introduce a new macro
that will load the phyiscal address of a symbol.

Lastly, use the new macro to replace all the current open-coded version.

Note that most of the comments associated to the code changed have been
removed because the code is now self-explanatory.

Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
---
  xen/arch/arm/arm32/head.S | 23 +++++++++++------------
  1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index c837d3054cf9..77f0a619ca51 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -65,6 +65,11 @@
          .endif
  .endm
+.macro load_paddr rb, sym
+        ldr   \rb, =\sym
+        add   \rb, \rb, r10
+.endm
+
All the macros in this file have a comment so it'd be useful to follow this 
convention.
This is not really a convention. Most of the macros are non-trivial (e.g. they may clobber registers).

The comment I have in mind here would be:

"Load the physical address of \sym in \rb"

I am fairly confident that anyone can understand from the ".macro" line... So I don't feel the comment is necessary.

Cheers,

--
Julien Grall



 


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