[PATCH 02/12] xen/arm: fix get_cpu_info() when built with clang

From: Julien Grall <julien.grall@arm.com>
To: xen-devel@lists.xenproject.org
Cc: Artem_Mygaiev@epam.com, Oleksandr_Tyshchenko@epam.com,
	Julien Grall <julien.grall@arm.com>,
	sstabellini@kernel.org, Andrii_Anisov@epam.com
Subject: [PATCH 02/12] xen/arm: fix get_cpu_info() when built with clang
Date: Wed, 27 Mar 2019 18:45:21 +0000	[thread overview]
Message-ID: <20190327184531.30986-3-julien.grall@arm.com> (raw)
In-Reply-To: <20190327184531.30986-1-julien.grall@arm.com>

Clang understands the GCCism in use here, but still complains that sp is
unitialised. In such cases, resort to the older versions of this code,
which directly read sp into the temporary variable.

Note that we still keep the GCCism in the default case, as it causes GCC
to create rather better assembly.

This is based on the x86 counterpart.

Signed-off-by: Julien Grall <julien.grall@arm.com>
---
 xen/include/asm-arm/current.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/xen/include/asm-arm/current.h b/xen/include/asm-arm/current.h
index c4af66fbb9..6b7c1df64d 100644
--- a/xen/include/asm-arm/current.h
+++ b/xen/include/asm-arm/current.h
@@ -28,8 +28,16 @@ struct cpu_info {
 
 static inline struct cpu_info *get_cpu_info(void)
 {
+#ifdef __clang__
+    unsigned long sp;
+
+    asm ("mov %0, sp" : "=r" (sp));
+#else
     register unsigned long sp asm ("sp");
-    return (struct cpu_info *)((sp & ~(STACK_SIZE - 1)) + STACK_SIZE - sizeof(struct cpu_info));
+#endif
+
+    return (struct cpu_info *)((sp & ~(STACK_SIZE - 1)) +
+                               STACK_SIZE - sizeof(struct cpu_info));
 }
 
 #define guest_cpu_user_regs() (&get_cpu_info()->guest_cpu_user_regs)
-- 
2.11.0


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