microblaze: Remove r0_ram pointer and PTO alignment

r0_ram pool was used for saving/restoring register
content if hw exception happen. This poll was replaced by
pt_pool_space with PT_SIZE size.
Based on this change SAVE_STATE_ARG_SPACE was removed which
caused that PTO offset is zero that's why is also removed.

r0_ram space was used as scratchpad by v850. In early
Microblaze Linux developing phase was this part of code
blindly copied.
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/include/asm/entry.h

@@ -31,40 +31,4 @@ DECLARE_PER_CPU(unsigned int, R11_SAVE); /* Temp variable for entry */
 DECLARE_PER_CPU(unsigned int, CURRENT_SAVE); /* Saved current pointer */
 # endif /* __ASSEMBLY__ */
 
-#ifndef CONFIG_MMU
-
-/* noMMU hasn't any space for args */
-# define STATE_SAVE_ARG_SPACE	(0)
-
-#else /* CONFIG_MMU */
-
-/* If true, system calls save and restore all registers (except result
- * registers, of course).  If false, then `call clobbered' registers
- * will not be preserved, on the theory that system calls are basically
- * function calls anyway, and the caller should be able to deal with it.
- * This is a security risk, of course, as `internal' values may leak out
- * after a system call, but that certainly doesn't matter very much for
- * a processor with no MMU protection!  For a protected-mode kernel, it
- * would be faster to just zero those registers before returning.
- *
- * I can not rely on the glibc implementation. If you turn it off make
- * sure that r11/r12 is saved in user-space. --KAA
- *
- * These are special variables using by the kernel trap/interrupt code
- * to save registers in, at a time when there are no spare registers we
- * can use to do so, and we can't depend on the value of the stack
- * pointer.  This means that they must be within a signed 16-bit
- * displacement of 0x00000000.
- */
-
-/* A `state save frame' is a struct pt_regs preceded by some extra space
- * suitable for a function call stack frame. */
-
-/* Amount of room on the stack reserved for arguments and to satisfy the
- * C calling conventions, in addition to the space used by the struct
- * pt_regs that actually holds saved values. */
-#define STATE_SAVE_ARG_SPACE	(6*4) /* Up to six arguments */
-
-#endif /* CONFIG_MMU */
-
 #endif /* _ASM_MICROBLAZE_ENTRY_H */

arch/microblaze/include/asm/processor.h

@@ -155,7 +155,7 @@ unsigned long get_wchan(struct task_struct *p);
 #  define task_regs(task) ((struct pt_regs *)task_tos(task) - 1)
 
 #  define task_pt_regs_plus_args(tsk) \
-	(((void *)task_pt_regs(tsk)) - STATE_SAVE_ARG_SPACE)
+	((void *)task_pt_regs(tsk))
 
 #  define task_sp(task)	(task_regs(task)->r1)
 #  define task_pc(task)	(task_regs(task)->pc)

arch/microblaze/kernel/hw_exception_handler.S

@@ -93,7 +93,7 @@
 		lwi	r6, r1, PT_R6;		\
 		lwi	r11, r1, PT_R11;	\
 		lwi	r31, r1, PT_R31;	\
-		lwi	r1, r0, TOPHYS(r0_ram + 0);
+		lwi	r1, r1, PT_R1;
 #endif /* CONFIG_MMU */
 
 #define LWREG_NOP			\
@@ -208,8 +208,8 @@
  *      |      .      |
  *      |      .      |
  *
- * NO_MMU kernel use the same r0_ram pointed space - look to vmlinux.lds.S
- * which is used for storing register values - old style was, that value were
+ * MMU kernel uses the same 'pt_pool_space' pointed space
+ * which is used for storing register values - noMMu style was, that values were
  * stored in stack but in case of failure you lost information about register.
  * Currently you can see register value in memory in specific place.
  * In compare to with previous solution the speed should be the same.
@@ -228,8 +228,12 @@
  */
 
 /* wrappers to restore state before coming to entry.S */
-
 #ifdef CONFIG_MMU
+.section .data
+.align 4
+pt_pool_space:
+	.space	PT_SIZE
+
 #ifdef DEBUG
 /* Create space for exception counting. */
 .section .data
@@ -299,10 +303,10 @@ _hw_exception_handler:
 #ifndef CONFIG_MMU
 	addik	r1, r1, -(EX_HANDLER_STACK_SIZ); /* Create stack frame */
 #else
-	swi	r1, r0, TOPHYS(r0_ram + 0); /* GET_SP */
+	swi	r1, r0, TOPHYS(pt_pool_space + PT_R1); /* GET_SP */
 	/* Save date to kernel memory. Here is the problem
 	 * when you came from user space */
-	ori	r1, r0, TOPHYS(r0_ram + 28);
+	ori	r1, r0, TOPHYS(pt_pool_space);
 #endif
 	swi	r3, r1, PT_R3
 	swi	r4, r1, PT_R4

arch/microblaze/kernel/process.c

@@ -159,7 +159,7 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
 	}
 
 	/* FIXME STATE_SAVE_PT_OFFSET; */
-	ti->cpu_context.r1  = (unsigned long)childregs - STATE_SAVE_ARG_SPACE;
+	ti->cpu_context.r1  = (unsigned long)childregs;
 	/* we should consider the fact that childregs is a copy of the parent
 	 * regs which were saved immediately after entering the kernel state
 	 * before enabling VM. This MSR will be restored in switch_to and

arch/microblaze/kernel/signal.c

@@ -93,7 +93,7 @@ static int restore_sigcontext(struct pt_regs *regs,
 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 {
 	struct rt_sigframe __user *frame =
-		(struct rt_sigframe __user *)(regs->r1 + STATE_SAVE_ARG_SPACE);
+		(struct rt_sigframe __user *)(regs->r1);
 
 	sigset_t set;
 	int rval;
@@ -247,7 +247,7 @@ static void setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 		goto give_sigsegv;
 
 	/* Set up registers for signal handler */
-	regs->r1 = (unsigned long) frame - STATE_SAVE_ARG_SPACE;
+	regs->r1 = (unsigned long) frame;
 
 	/* Signal handler args: */
 	regs->r5 = signal; /* arg 0: signum */

arch/microblaze/kernel/vmlinux.lds.S

@@ -70,11 +70,6 @@ SECTIONS {
 	RW_DATA_SECTION(32, PAGE_SIZE, THREAD_SIZE)
 	_edata = . ;
 
-	/* Reserve some low RAM for r0 based memory references */
-	. = ALIGN(0x4) ;
-	r0_ram = . ;
-	. = . +  PAGE_SIZE;	/* a page should be enough */
-
 	/* Under the microblaze ABI, .sdata and .sbss must be contiguous */
 	. = ALIGN(8);
 	.sdata : AT(ADDR(.sdata) - LOAD_OFFSET) {