[PATCH v2] xen/arm: un-break build with clang

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

clang doesn't like extern with __attribute__((__used__)):

  ./arch/arm/include/asm/setup.h:171:8: error: 'used' attribute ignored 
[-Werror,-Wignored-attributes]
  extern DEFINE_BOOT_PAGE_TABLE(boot_pgtable);
         ^
  ./arch/arm/include/asm/lpae.h:273:29: note: expanded from macro 
'DEFINE_BOOT_PAGE_TABLE'
  lpae_t __aligned(PAGE_SIZE) __section(".data.page_aligned")                   
\
                              ^
  ./include/xen/compiler.h:71:27: note: expanded from macro '__section'
  #define __section(s)      __used __attribute__((__section__(s)))
                            ^
  ./include/xen/compiler.h:104:39: note: expanded from macro '__used'
  #define __used         __attribute__((__used__))
                                        ^

Simplify the declarations by getting rid of the macro (and thus the
__aligned/__section/__used attributes) in the header. No functional change
intended as the macro/attributes are present in the respective definitions in
xen/arch/arm/mm.c.

Fixes: 1c78d76b67e1 ("xen/arm64: mm: Introduce helpers to 
prepare/enable/disable the identity mapping")
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
v1->v2:
* simplify by getting rid of the macro per Andrew's suggestion

---
I tested with clang 12 and clang 16

Here is my make command line:
make -j $(nproc) \
    clang=y \
    CC="clang --target=aarch64-none-linux-gnu -march=armv8a+nocrypto" \
    CXX="clang++ --target=aarch64-none-linux-gnu -march=armv8a+nocrypto" \
    HOSTCC=clang \
    HOSTCXX=clang++ \
    XEN_TARGET_ARCH=arm64 \
    CROSS_COMPILE=aarch64-none-linux-gnu- \
    dist-xen
---
 xen/arch/arm/include/asm/setup.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/include/asm/setup.h b/xen/arch/arm/include/asm/setup.h
index 38e2ce255fcf..1dbf3ced8079 100644
--- a/xen/arch/arm/include/asm/setup.h
+++ b/xen/arch/arm/include/asm/setup.h
@@ -168,13 +168,13 @@ u32 device_tree_get_u32(const void *fdt, int node,
 int map_range_to_domain(const struct dt_device_node *dev,
                         u64 addr, u64 len, void *data);
 
-extern DEFINE_BOOT_PAGE_TABLE(boot_pgtable);
+extern lpae_t boot_pgtable[XEN_PT_LPAE_ENTRIES];
 
 #ifdef CONFIG_ARM_64
-extern DEFINE_BOOT_PAGE_TABLE(boot_first_id);
+extern lpae_t boot_first_id[XEN_PT_LPAE_ENTRIES];
 #endif
-extern DEFINE_BOOT_PAGE_TABLE(boot_second_id);
-extern DEFINE_BOOT_PAGE_TABLE(boot_third_id);
+extern lpae_t boot_second_id[XEN_PT_LPAE_ENTRIES];
+extern lpae_t boot_third_id[XEN_PT_LPAE_ENTRIES];
 
 /* Find where Xen will be residing at runtime and return a PT entry */
 lpae_t pte_of_xenaddr(vaddr_t);
-- 
2.40.1