xtensa: move fast exception handlers close to vectors

On XIP kernels it makes sense to have exception vectors and fast
exception handlers together (in a fast memory). In addition, with MTD
XIP support both vectors and fast exception handlers must be outside of
the FLASH.

Add section .exception.text and move fast exception handlers to it.
Put it together with vectors when vectors are outside of the .text.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/include/asm/asmmacro.h

@@ -237,4 +237,6 @@
 #error Unsupported Xtensa ABI
 #endif
 
+#define __XTENSA_HANDLER	.section ".exception.text", "ax"
+
 #endif /* _XTENSA_ASMMACRO_H */

arch/xtensa/kernel/coprocessor.S

@@ -58,6 +58,8 @@
 	.endif;								\
 	.long THREAD_XTREGS_CP##x
 
+	__XTENSA_HANDLER
+
 	SAVE_CP_REGS(0)
 	SAVE_CP_REGS(1)
 	SAVE_CP_REGS(2)
@@ -76,7 +78,6 @@
 	LOAD_CP_REGS(6)
 	LOAD_CP_REGS(7)
 
-	.section ".rodata", "a"
 	.align 4
 .Lsave_cp_regs_jump_table:
 	SAVE_CP_REGS_TAB(0)
@@ -98,8 +99,6 @@
 	LOAD_CP_REGS_TAB(6)
 	LOAD_CP_REGS_TAB(7)
 
-	.previous
-
 /*
  * coprocessor_flush(struct thread_info*, index)
  *                             a2        a3

arch/xtensa/kernel/entry.S

@@ -939,6 +939,9 @@ ENDPROC(unrecoverable_exception)
 
 /* -------------------------- FAST EXCEPTION HANDLERS ----------------------- */
 
+	__XTENSA_HANDLER
+	.literal_position
+
 /*
  * Fast-handler for alloca exceptions
  *
@@ -1024,7 +1027,7 @@ ENDPROC(fast_alloca)
 ENTRY(fast_illegal_instruction_user)
 
 	rsr	a0, ps
-	bbsi.l	a0, PS_WOE_BIT, user_exception
+	bbsi.l	a0, PS_WOE_BIT, 1f
 	s32i	a3, a2, PT_AREG3
 	movi	a3, PS_WOE_MASK
 	or	a0, a0, a3
@@ -1033,6 +1036,8 @@ ENTRY(fast_illegal_instruction_user)
 	l32i	a0, a2, PT_AREG0
 	rsr	a2, depc
 	rfe
+1:
+	call0	user_exception
 
 ENDPROC(fast_illegal_instruction_user)
 #endif
@@ -1071,7 +1076,7 @@ ENTRY(fast_syscall_user)
 	_beqz	a0, fast_syscall_spill_registers
 	_beqi	a0, __NR_xtensa, fast_syscall_xtensa
 
-	j	user_exception
+	call0	user_exception
 
 ENDPROC(fast_syscall_user)
 
@@ -1762,8 +1767,8 @@ ENTRY(fast_second_level_miss)
 
 	rsr	a2, ps
 	bbsi.l	a2, PS_UM_BIT, 1f
-	j	_kernel_exception
-1:	j	_user_exception
+	call0	_kernel_exception
+1:	call0	_user_exception
 
 ENDPROC(fast_second_level_miss)
 
@@ -1859,13 +1864,14 @@ ENTRY(fast_store_prohibited)
 
 	rsr	a2, ps
 	bbsi.l	a2, PS_UM_BIT, 1f
-	j	_kernel_exception
-1:	j	_user_exception
+	call0	_kernel_exception
+1:	call0	_user_exception
 
 ENDPROC(fast_store_prohibited)
 
 #endif /* CONFIG_MMU */
 
+	.text
 /*
  * System Calls.
  *

arch/xtensa/kernel/setup.c

@@ -284,6 +284,8 @@ extern char _UserExceptionVector_text_start;
 extern char _UserExceptionVector_text_end;
 extern char _DoubleExceptionVector_text_start;
 extern char _DoubleExceptionVector_text_end;
+extern char _exception_text_start;
+extern char _exception_text_end;
 #if XCHAL_EXCM_LEVEL >= 2
 extern char _Level2InterruptVector_text_start;
 extern char _Level2InterruptVector_text_end;
@@ -363,6 +365,8 @@ void __init setup_arch(char **cmdline_p)
 	mem_reserve(__pa(&_DoubleExceptionVector_text_start),
 		    __pa(&_DoubleExceptionVector_text_end));
 
+	mem_reserve(__pa(&_exception_text_start),
+		    __pa(&_exception_text_end));
 #if XCHAL_EXCM_LEVEL >= 2
 	mem_reserve(__pa(&_Level2InterruptVector_text_start),
 		    __pa(&_Level2InterruptVector_text_end));

arch/xtensa/kernel/vectors.S

@@ -43,6 +43,7 @@
  */
 
 #include <linux/linkage.h>
+#include <asm/asmmacro.h>
 #include <asm/ptrace.h>
 #include <asm/current.h>
 #include <asm/asm-offsets.h>
@@ -477,7 +478,6 @@ _DoubleExceptionVector_handle_exception:
 
 ENDPROC(_DoubleExceptionVector)
 
-	.text
 /*
  * Fixup handler for TLB miss in double exception handler for window owerflow.
  * We get here with windowbase set to the window that was being spilled and
@@ -505,6 +505,7 @@ ENDPROC(_DoubleExceptionVector)
  * a3: exctable, original value in excsave1
  */
 
+	__XTENSA_HANDLER
 	.literal_position
 
 ENTRY(window_overflow_restore_a0_fixup)

arch/xtensa/kernel/vmlinux.lds.S

@@ -110,6 +110,8 @@ SECTIONS
   SECTION_VECTOR (.KernelExceptionVector.text, KERNEL_VECTOR_VADDR)
   SECTION_VECTOR (.UserExceptionVector.text, USER_VECTOR_VADDR)
   SECTION_VECTOR (.DoubleExceptionVector.text, DOUBLEEXC_VECTOR_VADDR)
+
+  *(.exception.text)
 #endif
 
     IRQENTRY_TEXT
@@ -190,6 +192,8 @@ SECTIONS
 		   .DoubleExceptionVector.text);
     RELOCATE_ENTRY(_DebugInterruptVector_text,
 		   .DebugInterruptVector.text);
+    RELOCATE_ENTRY(_exception_text,
+		   .exception.text);
 #endif
 #ifdef CONFIG_XIP_KERNEL
     RELOCATE_ENTRY(_xip_data, .data);
@@ -282,8 +286,7 @@ SECTIONS
 		  .DoubleExceptionVector.text,
 		  DOUBLEEXC_VECTOR_VADDR,
 		  .UserExceptionVector.text)
-
-  . = (LOADADDR( .DoubleExceptionVector.text ) + SIZEOF( .DoubleExceptionVector.text ) + 3) & ~ 3;
+#define LAST .DoubleExceptionVector.text
 
 #endif
 #if !defined(CONFIG_XIP_KERNEL) && defined(CONFIG_SMP)
@@ -292,10 +295,20 @@ SECTIONS
 		  .SecondaryResetVector.text,
 		  RESET_VECTOR1_VADDR,
 		  .DoubleExceptionVector.text)
-
-  . = LOADADDR(.SecondaryResetVector.text)+SIZEOF(.SecondaryResetVector.text);
+#undef LAST
+#define LAST .SecondaryResetVector.text
 
 #endif
+#ifdef CONFIG_VECTORS_OFFSET
+  SECTION_VECTOR (_exception_text,
+		  .exception.text,
+		  ,
+		  LAST)
+#undef LAST
+#define LAST .exception.text
+
+#endif
+  . = (LOADADDR(LAST) + SIZEOF(LAST) + 3) & ~ 3;
 
   . = ALIGN(PAGE_SIZE);