x86, xsave: struct _fpstate extensions to include extended state information

Bytes 464..511 in the current 512byte layout of fxsave/fxrstor
frame, are reserved for SW usage. On cpu's supporting xsave/xrstor, these bytes
are used to extended the fpstate pointer in the sigcontext, which now includes
the extended state information along with fpstate information.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 94 insertions, 6 deletions

diff --git a/include/asm-x86/processor.h b/include/asm-x86/processor.h
index 77b7af6b573b..eb4bd8c07730 100644
--- a/include/asm-x86/processor.h
+++ b/include/asm-x86/processor.h
@@ -322,7 +322,12 @@ struct i387_fxsave_struct {
         /* 16*16 bytes for each XMM-reg = 256 bytes:                    */
         u32                     xmm_space[64];
 
-        u32                     padding[24];
+        u32                     padding[12];
+
+        union {
+                u32             padding1[12];
+                u32             sw_reserved[12];
+        };
 
 } __attribute__((aligned(16)));
 
diff --git a/include/asm-x86/sigcontext.h b/include/asm-x86/sigcontext.h
index 24879c85b291..899fe2f8abb9 100644
--- a/include/asm-x86/sigcontext.h
+++ b/include/asm-x86/sigcontext.h
@@ -4,6 +4,40 @@
 #include <linux/compiler.h>
 #include <asm/types.h>
 
+#define FP_XSTATE_MAGIC1        0x46505853U
+#define FP_XSTATE_MAGIC2        0x46505845U
+#define FP_XSTATE_MAGIC2_SIZE   sizeof(FP_XSTATE_MAGIC2)
+
+/*
+ * bytes 464..511 in the current 512byte layout of fxsave/fxrstor frame
+ * are reserved for SW usage. On cpu's supporting xsave/xrstor, these bytes
+ * are used to extended the fpstate pointer in the sigcontext, which now
+ * includes the extended state information along with fpstate information.
+ *
+ * Presence of FP_XSTATE_MAGIC1 at the beginning of this SW reserved
+ * area and FP_XSTATE_MAGIC2 at the end of memory layout
+ * (extended_size - FP_XSTATE_MAGIC2_SIZE) indicates the presence of the
+ * extended state information in the memory layout pointed by the fpstate
+ * pointer in sigcontext.
+ */
+struct _fpx_sw_bytes {
+        __u32 magic1;           /* FP_XSTATE_MAGIC1 */
+        __u32 extended_size;    /* total size of the layout referred by
+                                 * fpstate pointer in the sigcontext.
+                                 */
+        __u64 xstate_bv;
+                                /* feature bit mask (including fp/sse/extended
+                                 * state) that is present in the memory
+                                 * layout.
+                                 */
+        __u32 xstate_size;      /* actual xsave state size, based on the
+                                 * features saved in the layout.
+                                 * 'extended_size' will be greater than
+                                 * 'xstate_size'.
+                                 */
+        __u32 padding[7];       /*  for future use. */
+};
+
 #ifdef __i386__
 /*
  * As documented in the iBCS2 standard..
@@ -53,7 +87,13 @@ struct _fpstate {
         unsigned long   reserved;
         struct _fpxreg  _fxsr_st[8];    /* FXSR FPU reg data is ignored */
         struct _xmmreg  _xmm[8];
-        unsigned long   padding[56];
+        unsigned long   padding1[44];
+
+        union {
+                unsigned long   padding2[12];
+                struct _fpx_sw_bytes sw_reserved; /* represents the extended
+                                                   * state info */
+        };
 };
 
 #define X86_FXSR_MAGIC          0x0000
@@ -79,7 +119,15 @@ struct sigcontext {
         unsigned long flags;
         unsigned long sp_at_signal;
         unsigned short ss, __ssh;
-        struct _fpstate __user *fpstate;
+
+        /*
+         * fpstate is really (struct _fpstate *) or (struct _xstate *)
+         * depending on the FP_XSTATE_MAGIC1 encoded in the SW reserved
+         * bytes of (struct _fpstate) and FP_XSTATE_MAGIC2 present at the end
+         * of extended memory layout. See comments at the defintion of
+         * (struct _fpx_sw_bytes)
+         */
+        void __user *fpstate;           /* zero when no FPU/extended context */
         unsigned long oldmask;
         unsigned long cr2;
 };
@@ -130,7 +178,12 @@ struct _fpstate {
         __u32   mxcsr_mask;
         __u32   st_space[32];   /* 8*16 bytes for each FP-reg */
         __u32   xmm_space[64];  /* 16*16 bytes for each XMM-reg  */
-        __u32   reserved2[24];
+        __u32   reserved2[12];
+        union {
+                __u32   reserved3[12];
+                struct _fpx_sw_bytes sw_reserved; /* represents the extended
+                                                   * state information */
+        };
 };
 
 #ifdef __KERNEL__
@@ -161,7 +214,15 @@ struct sigcontext {
         unsigned long trapno;
         unsigned long oldmask;
         unsigned long cr2;
-        struct _fpstate __user *fpstate;        /* zero when no FPU context */
+
+        /*
+         * fpstate is really (struct _fpstate *) or (struct _xstate *)
+         * depending on the FP_XSTATE_MAGIC1 encoded in the SW reserved
+         * bytes of (struct _fpstate) and FP_XSTATE_MAGIC2 present at the end
+         * of extended memory layout. See comments at the defintion of
+         * (struct _fpx_sw_bytes)
+         */
+        void __user *fpstate;           /* zero when no FPU/extended context */
         unsigned long reserved1[8];
 };
 #else /* __KERNEL__ */
@@ -202,4 +263,22 @@ struct sigcontext {
 
 #endif /* !__i386__ */
 
+struct _xsave_hdr {
+        u64 xstate_bv;
+        u64 reserved1[2];
+        u64 reserved2[5];
+};
+
+/*
+ * Extended state pointed by the fpstate pointer in the sigcontext.
+ * In addition to the fpstate, information encoded in the xstate_hdr
+ * indicates the presence of other extended state information
+ * supported by the processor and OS.
+ */
+struct _xstate {
+        struct _fpstate fpstate;
+        struct _xsave_hdr xstate_hdr;
+        /* new processor state extensions go here */
+};
+
 #endif /* ASM_X86__SIGCONTEXT_H */
diff --git a/include/asm-x86/sigcontext32.h b/include/asm-x86/sigcontext32.h
index 4e2ec732dd01..8c347032c2f2 100644
--- a/include/asm-x86/sigcontext32.h
+++ b/include/asm-x86/sigcontext32.h
@@ -40,7 +40,11 @@ struct _fpstate_ia32 {
         __u32   reserved;
         struct _fpxreg  _fxsr_st[8];
         struct _xmmreg  _xmm[8];        /* It's actually 16 */
-        __u32   padding[56];
+        __u32   padding[44];
+        union {
+                __u32 padding2[12];
+                struct _fpx_sw_bytes sw_reserved;
+        };
 };
 
 struct sigcontext_ia32 {