[ARM PATCH] 1866/4: kernel support for iWMMXt present on some XScale cores

Patch from Nicolas Pitre

This is required for a system with user space binaries using iWMMXt 
instructions to even boot (revised again).

It also moves defines for thread_info offsets from  magic static
values to the auto generated asm/constants.h in order to better
cope with changing structure offsets and avoid user errors.

3 files changed, 49 insertions, 16 deletions

diff --git a/include/asm-arm/elf.h b/include/asm-arm/elf.h
index b67e06c0f588e4..29533be8be619e 100644
--- a/include/asm-arm/elf.h
+++ b/include/asm-arm/elf.h
@@ -1,6 +1,8 @@
 #ifndef __ASMARM_ELF_H
 #define __ASMARM_ELF_H
 
+#include <linux/config.h>
+
 /*
  * ELF register definitions..
  */
@@ -14,6 +16,7 @@ typedef unsigned long elf_freg_t[3];
 
 #define EM_ARM	40
 #define EF_ARM_APCS26 0x08
+#define EF_ARM_SOFT_FLOAT 0x200
 
 #define R_ARM_NONE	0
 #define R_ARM_PC24	1
@@ -91,6 +94,8 @@ extern char elf_platform[];
 	(( (elf_hwcap & HWCAP_26BIT) && (x)->e_flags & EF_ARM_APCS26) || \
 	  ((x)->e_flags & EF_ARM_APCS26) == 0)
 
+#ifndef CONFIG_IWMMXT
+
 /* Old NetWinder binaries were compiled in such a way that the iBCS
    heuristic always trips on them.  Until these binaries become uncommon
    enough not to care, don't trust the `ibcs' flag here.  In any case
@@ -99,6 +104,28 @@ extern char elf_platform[];
 #define SET_PERSONALITY(ex,ibcs2) \
 	set_personality(((ex).e_flags&EF_ARM_APCS26 ?PER_LINUX :PER_LINUX_32BIT))
 
+#else
+
+/*
+ * All iWMMXt capable CPUs don't support 26-bit mode.  Yet they can run
+ * legacy binaries which used to contain FPA11 floating point instructions
+ * that have always been emulated by the kernel.  PFA11 and iWMMXt overlap
+ * on coprocessor 1 space though.  We therefore must decide if given task
+ * is allowed to use CP 0 and 1 for iWMMXt, or if they should be blocked
+ * at all times for the prefetch exception handler to catch FPA11 opcodes
+ * and emulate them.  The best indication to discriminate those two cases
+ * is the SOFT_FLOAT flag in the ELF header.
+ */
+
+#define SET_PERSONALITY(ex,ibcs2) \
+do { \
+	set_personality(PER_LINUX_32BIT); \
+	if ((ex).e_flags & EF_ARM_SOFT_FLOAT) \
+		set_thread_flag(TIF_USING_IWMMXT); \
+} while (0)
+
+#endif
+
 #endif
 
 #endif
diff --git a/include/asm-arm/fpstate.h b/include/asm-arm/fpstate.h
index 7492cfa21f7a57..f7430e3aa55d2e 100644
--- a/include/asm-arm/fpstate.h
+++ b/include/asm-arm/fpstate.h
@@ -11,7 +11,7 @@
 #ifndef __ASM_ARM_FPSTATE_H
 #define __ASM_ARM_FPSTATE_H
 
-#define FP_SIZE 35
+#include <linux/config.h>
 
 #ifndef __ASSEMBLY__
 
@@ -43,19 +43,32 @@ union vfp_state {
 extern void vfp_flush_thread(union vfp_state *);
 extern void vfp_release_thread(union vfp_state *);
 
+#define FP_HARD_SIZE 35
+
 struct fp_hard_struct {
-	unsigned int save[FP_SIZE];		/* as yet undefined */
+	unsigned int save[FP_HARD_SIZE];		/* as yet undefined */
 };
 
+#define FP_SOFT_SIZE 35
+
 struct fp_soft_struct {
-	unsigned int save[FP_SIZE];		/* undefined information */
+	unsigned int save[FP_SOFT_SIZE];		/* undefined information */
+};
+
+struct iwmmxt_struct {
+	unsigned int save[0x98/sizeof(int) + 1];
 };
 
 union fp_state {
 	struct fp_hard_struct	hard;
 	struct fp_soft_struct	soft;
+#ifdef CONFIG_IWMMXT
+	struct iwmmxt_struct	iwmmxt;
+#endif
 };
 
+#define FP_SIZE (sizeof(union fp_state) / sizeof(int))
+
 #endif
 
 #endif
diff --git a/include/asm-arm/thread_info.h b/include/asm-arm/thread_info.h
index b3ef76481942aa..9f08222633aa04 100644
--- a/include/asm-arm/thread_info.h
+++ b/include/asm-arm/thread_info.h
@@ -100,19 +100,10 @@ extern void free_thread_info(struct thread_info *);
 #define thread_saved_fp(tsk)	\
 	((unsigned long)((tsk)->thread_info->cpu_context.fp))
 
-#else /* !__ASSEMBLY__ */
-
-#define TI_FLAGS	0
-#define TI_PREEMPT	4
-#define TI_ADDR_LIMIT	8
-#define TI_TASK		12
-#define TI_EXEC_DOMAIN	16
-#define TI_CPU		20
-#define TI_CPU_DOMAIN	24
-#define TI_CPU_SAVE	28
-#define TI_USED_CP	76
-#define TI_FPSTATE	(TI_USED_CP+16)
-#define TI_VFPSTATE	(TI_FPSTATE+FP_SIZE*4)
+extern void iwmmxt_task_disable(struct thread_info *);
+extern void iwmmxt_task_copy(struct thread_info *, void *);
+extern void iwmmxt_task_restore(struct thread_info *, void *);
+extern void iwmmxt_task_release(struct thread_info *);
 
 #endif
 
@@ -133,6 +124,7 @@ extern void free_thread_info(struct thread_info *);
 #define TIF_SYSCALL_TRACE	8
 #define TIF_USED_FPU		16
 #define TIF_POLLING_NRFLAG	17
+#define TIF_USING_IWMMXT	18
 
 #define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
 #define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
@@ -140,6 +132,7 @@ extern void free_thread_info(struct thread_info *);
 #define _TIF_SYSCALL_TRACE	(1 << TIF_SYSCALL_TRACE)
 #define _TIF_USED_FPU		(1 << TIF_USED_FPU)
 #define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
+#define _TIF_USING_IWMMXT	(1 << TIF_USING_IWMMXT)
 
 /*
  * Change these and you break ASM code in entry-common.S