[xen master] xen/arm32: cmpxchg: Simplify the cmpxchg implementation

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[xen master] xen/arm32: cmpxchg: Simplify the cmpxchg implementation

patchbot
commit 2d2ccf4355a182232b2c60a3bca4c15210e8b4b6
Author:     Julien Grall <[hidden email]>
AuthorDate: Mon Apr 29 15:05:22 2019 +0100
Commit:     Julien Grall <[hidden email]>
CommitDate: Fri Jun 14 14:27:32 2019 +0100

    xen/arm32: cmpxchg: Simplify the cmpxchg implementation
   
    The only difference between each case of the cmpxchg is the size of
    used. Rather than duplicating the code, provide a macro to generate each
    cases.
   
    This makes the code easier to read and modify.
   
    While doing the rework, the case for 64-bit cmpxchg is removed. This is
    unused today (already commented) and it would not be possible to use
    it directly.
   
    This is part of XSA-295.
   
    Signed-off-by: Julien Grall <[hidden email]>
    Reviewed-by: Stefano Stabellini <[hidden email]>
---
 xen/include/asm-arm/arm32/cmpxchg.h | 84 ++++++++++++++-----------------------
 1 file changed, 31 insertions(+), 53 deletions(-)

diff --git a/xen/include/asm-arm/arm32/cmpxchg.h b/xen/include/asm-arm/arm32/cmpxchg.h
index 03e0bed3a6..471a9e3a3f 100644
--- a/xen/include/asm-arm/arm32/cmpxchg.h
+++ b/xen/include/asm-arm/arm32/cmpxchg.h
@@ -52,72 +52,50 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size
  * indicated by comparing RETURN with OLD.
  */
 
-extern void __bad_cmpxchg(volatile void *ptr, int size);
+extern unsigned long __bad_cmpxchg(volatile void *ptr, int size);
+
+#define __CMPXCHG_CASE(sz, name) \
+static inline unsigned long __cmpxchg_case_##name(volatile void *ptr, \
+  unsigned long old, \
+  unsigned long new) \
+{ \
+ unsigned long oldval, res; \
+ \
+ do { \
+ asm volatile("@ __cmpxchg_case_" #name "\n" \
+ " ldrex" #sz " %1, [%2]\n" \
+ " mov %0, #0\n" \
+ " teq %1, %3\n" \
+ " strex" #sz "eq %0, %4, [%2]\n" \
+ : "=&r" (res), "=&r" (oldval) \
+ : "r" (ptr), "Ir" (old), "r" (new) \
+ : "memory", "cc"); \
+ } while (res); \
+ \
+ return oldval; \
+}
+
+__CMPXCHG_CASE(b, 1)
+__CMPXCHG_CASE(h, 2)
+__CMPXCHG_CASE( , 4)
 
 static always_inline unsigned long __cmpxchg(
     volatile void *ptr, unsigned long old, unsigned long new, int size)
 {
- unsigned long oldval, res;
-
  prefetchw((const void *)ptr);
 
  switch (size) {
  case 1:
- do {
- asm volatile("@ __cmpxchg1\n"
- " ldrexb %1, [%2]\n"
- " mov %0, #0\n"
- " teq %1, %3\n"
- " strexbeq %0, %4, [%2]\n"
- : "=&r" (res), "=&r" (oldval)
- : "r" (ptr), "Ir" (old), "r" (new)
- : "memory", "cc");
- } while (res);
- break;
+ return __cmpxchg_case_1(ptr, old, new);
  case 2:
- do {
- asm volatile("@ __cmpxchg2\n"
- " ldrexh %1, [%2]\n"
- " mov %0, #0\n"
- " teq %1, %3\n"
- " strexheq %0, %4, [%2]\n"
- : "=&r" (res), "=&r" (oldval)
- : "r" (ptr), "Ir" (old), "r" (new)
- : "memory", "cc");
- } while (res);
- break;
+ return __cmpxchg_case_2(ptr, old, new);
  case 4:
- do {
- asm volatile("@ __cmpxchg4\n"
- " ldrex %1, [%2]\n"
- " mov %0, #0\n"
- " teq %1, %3\n"
- " strexeq %0, %4, [%2]\n"
- : "=&r" (res), "=&r" (oldval)
- : "r" (ptr), "Ir" (old), "r" (new)
- : "memory", "cc");
-    } while (res);
-    break;
-#if 0
- case 8:
- do {
- asm volatile("@ __cmpxchg8\n"
- " ldrexd %1, [%2]\n"
- " mov %0, #0\n"
- " teq %1, %3\n"
- " strexdeq %0, %4, [%2]\n"
- : "=&r" (res), "=&r" (oldval)
- : "r" (ptr), "Ir" (old), "r" (new)
- : "memory", "cc");
- } while (res);
- break;
-#endif
+ return __cmpxchg_case_4(ptr, old, new);
  default:
- __bad_cmpxchg(ptr, size);
- oldval = 0;
+ return __bad_cmpxchg(ptr, size);
  }
 
- return oldval;
+ ASSERT_UNREACHABLE();
 }
 
 static always_inline unsigned long __cmpxchg_mb(volatile void *ptr,
--
generated by git-patchbot for /home/xen/git/xen.git#master

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