[Xen-changelog] [xen staging] xen/arm64: head: Introduce a macro to get a PC-relative address of a symbol

[patchbot@xxxxxxx]

commit b352d468f4d2f12f8ee6a0f6d81cdd8010cc8699
Author:     Julien Grall <julien.grall@xxxxxxx>
AuthorDate: Mon Jun 17 14:51:21 2019 +0100
Commit:     Julien Grall <julien.grall@xxxxxxx>
CommitDate: Sat Sep 7 12:09:49 2019 +0100

    xen/arm64: head: Introduce a macro to get a PC-relative address of a symbol
    
    Arm64 provides instructions to load a PC-relative address, but with some
    limitations:
       - adr is enable to cope with +/-1MB
       - adrp is enale to cope with +/-4GB but relative to a 4KB page
         address
    
    Because of that, the code requires to use 2 instructions to load any Xen
    symbol. To make the code more obvious, introducing a new macro adr_l is
    introduced.
    
    The new macro is used to replace a couple of open-coded use in
    efi_xen_start.
    
    The macro is copied from Linux 5.2-rc4.
    
    Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
    Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/arch/arm/arm64/head.S | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 12a7edfdd2..f8da3c8cc5 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -112,6 +112,18 @@
 
 #endif /* !CONFIG_EARLY_PRINTK */
 
+/*
+ * Pseudo-op for PC relative adr <reg>, <symbol> where <symbol> is
+ * within the range +/- 4GB of the PC.
+ *
+ * @dst: destination register (64 bit wide)
+ * @sym: name of the symbol
+ */
+.macro  adr_l, dst, sym
+        adrp \dst, \sym
+        add  \dst, \dst, :lo12:\sym
+.endm
+
 /* Load the physical address of a symbol into xb */
 .macro load_paddr xb, sym
         ldr \xb, =\sym
@@ -817,11 +829,9 @@ ENTRY(efi_xen_start)
          * Flush dcache covering current runtime addresses
          * of xen text/data. Then flush all of icache.
          */
-        adrp  x1, _start
-        add   x1, x1, #:lo12:_start
+        adr_l x1, _start
         mov   x0, x1
-        adrp  x2, _end
-        add   x2, x2, #:lo12:_end
+        adr_l x2, _end
         sub   x1, x2, x1
 
         bl    __flush_dcache_area
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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