X-Git-Url: http://pilppa.org/gitweb/?a=blobdiff_plain;f=include%2Flinux%2Fcompiler-gcc.h;h=a3ed7cb8ca346e7fba7170022c46928480b896a6;hb=4496d937a518fde0d0e1980e4ab470cedb4b50cd;hp=af40f8eb86f0a513a7d8e82dcd0c7a30bd178649;hpb=db30c70575822cc84d87b5613c19cac24734b99f;p=linux-2.6-omap-h63xx.git

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index af40f8eb86f..a3ed7cb8ca3 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -11,9 +11,19 @@
 /* The "volatile" is due to gcc bugs */
 #define barrier() __asm__ __volatile__("": : :"memory")
 
-/* This macro obfuscates arithmetic on a variable address so that gcc
-   shouldn't recognize the original var, and make assumptions about it */
 /*
+ * This macro obfuscates arithmetic on a variable address so that gcc
+ * shouldn't recognize the original var, and make assumptions about it.
+ *
+ * This is needed because the C standard makes it undefined to do
+ * pointer arithmetic on "objects" outside their boundaries and the
+ * gcc optimizers assume this is the case. In particular they
+ * assume such arithmetic does not wrap.
+ *
+ * A miscompilation has been observed because of this on PPC.
+ * To work around it we hide the relationship of the pointer and the object
+ * using this macro.
+ *
  * Versions of the ppc64 compiler before 4.1 had a bug where use of
  * RELOC_HIDE could trash r30. The bug can be worked around by changing
  * the inline assembly constraint from =g to =r, in this particular
@@ -42,7 +52,15 @@
 #define __deprecated			__attribute__((deprecated))
 #define __packed			__attribute__((packed))
 #define __weak				__attribute__((weak))
-#define __naked				__attribute__((naked))
+
+/*
+ * it doesn't make sense on ARM (currently the only user of __naked) to trace
+ * naked functions because then mcount is called without stack and frame pointer
+ * being set up and there is no chance to restore the lr register to the value
+ * before mcount was called.
+ */
+#define __naked				__attribute__((naked)) notrace
+
 #define __noreturn			__attribute__((noreturn))
 
 /*