[PATCH] i386: Basic definitions for i386-pda

This patch has the basic definitions of struct i386_pda, and the segment
selector in the GDT.

asm-i386/pda.h is more or less a direct copy of asm-x86_64/pda.h.  The most
interesting difference is the use of _proxy_pda, which is used to give gcc a
model for the actual memory operations on the real pda structure.  No actual
reference is ever made to _proxy_pda, so it is never defined.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Chuck Ebbert <76306.1226@compuserve.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>

1 files changed, 95 insertions, 0 deletions

diff --git a/include/asm-i386/pda.h b/include/asm-i386/pda.h
new file mode 100644
index 000000000000..4c39ccb1305c
--- /dev/null
+++ b/include/asm-i386/pda.h
@@ -0,0 +1,95 @@
+/*
+   Per-processor Data Areas
+   Jeremy Fitzhardinge <jeremy@goop.org> 2006
+   Based on asm-x86_64/pda.h by Andi Kleen.
+ */
+#ifndef _I386_PDA_H
+#define _I386_PDA_H
+
+#include <linux/stddef.h>
+
+struct i386_pda
+{
+        struct i386_pda *_pda;          /* pointer to self */
+};
+
+extern struct i386_pda *_cpu_pda[];
+
+#define cpu_pda(i)      (_cpu_pda[i])
+
+#define pda_offset(field) offsetof(struct i386_pda, field)
+
+extern void __bad_pda_field(void);
+
+/* This variable is never instantiated.  It is only used as a stand-in
+   for the real per-cpu PDA memory, so that gcc can understand what
+   memory operations the inline asms() below are performing.  This
+   eliminates the need to make the asms volatile or have memory
+   clobbers, so gcc can readily analyse them. */
+extern struct i386_pda _proxy_pda;
+
+#define pda_to_op(op,field,val)                                         \
+        do {                                                            \
+                typedef typeof(_proxy_pda.field) T__;                   \
+                if (0) { T__ tmp__; tmp__ = (val); }                    \
+                switch (sizeof(_proxy_pda.field)) {                     \
+                case 1:                                                 \
+                        asm(op "b %1,%%gs:%c2"                          \
+                            : "+m" (_proxy_pda.field)                   \
+                            :"ri" ((T__)val),                           \
+                             "i"(pda_offset(field)));                   \
+                        break;                                          \
+                case 2:                                                 \
+                        asm(op "w %1,%%gs:%c2"                          \
+                            : "+m" (_proxy_pda.field)                   \
+                            :"ri" ((T__)val),                           \
+                             "i"(pda_offset(field)));                   \
+                        break;                                          \
+                case 4:                                                 \
+                        asm(op "l %1,%%gs:%c2"                          \
+                            : "+m" (_proxy_pda.field)                   \
+                            :"ri" ((T__)val),                           \
+                             "i"(pda_offset(field)));                   \
+                        break;                                          \
+                default: __bad_pda_field();                             \
+                }                                                       \
+        } while (0)
+
+#define pda_from_op(op,field)                                           \
+        ({                                                              \
+                typeof(_proxy_pda.field) ret__;                         \
+                switch (sizeof(_proxy_pda.field)) {                     \
+                case 1:                                                 \
+                        asm(op "b %%gs:%c1,%0"                          \
+                            : "=r" (ret__)                              \
+                            : "i" (pda_offset(field)),                  \
+                              "m" (_proxy_pda.field));                  \
+                        break;                                          \
+                case 2:                                                 \
+                        asm(op "w %%gs:%c1,%0"                          \
+                            : "=r" (ret__)                              \
+                            : "i" (pda_offset(field)),                  \
+                              "m" (_proxy_pda.field));                  \
+                        break;                                          \
+                case 4:                                                 \
+                        asm(op "l %%gs:%c1,%0"                          \
+                            : "=r" (ret__)                              \
+                            : "i" (pda_offset(field)),                  \
+                              "m" (_proxy_pda.field));                  \
+                        break;                                          \
+                default: __bad_pda_field();                             \
+                }                                                       \
+                ret__; })
+
+/* Return a pointer to a pda field */
+#define pda_addr(field)                                                 \
+        ((typeof(_proxy_pda.field) *)((unsigned char *)read_pda(_pda) + \
+                                      pda_offset(field)))
+
+#define read_pda(field) pda_from_op("mov",field)
+#define write_pda(field,val) pda_to_op("mov",field,val)
+#define add_pda(field,val) pda_to_op("add",field,val)
+#define sub_pda(field,val) pda_to_op("sub",field,val)
+#define or_pda(field,val) pda_to_op("or",field,val)
+
+#endif  /* _I386_PDA_H */