xtensa: allow merging vectors into .text section

Currently code for exception/IRQ vectors is stored in kernel image as
initialization data and is copied to its working addresses during
startup. It doesn't always make sense. In many cases vectors location
can be automatically decided at kernel link time and code can be placed
right there. This is especially useful for XIP kernel.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/include/asm/vectors.h

@@ -67,7 +67,11 @@ static inline unsigned long xtensa_get_kio_paddr(void)
 #endif /* CONFIG_MMU */
 
 #define RESET_VECTOR1_VADDR		(XCHAL_RESET_VECTOR1_VADDR)
+#ifdef CONFIG_VECTORS_OFFSET
 #define VECBASE_VADDR			(KERNELOFFSET - CONFIG_VECTORS_OFFSET)
+#else
+#define VECBASE_VADDR			_vecbase
+#endif
 
 #if defined(XCHAL_HAVE_VECBASE) && XCHAL_HAVE_VECBASE
 

arch/xtensa/kernel/setup.c

@@ -455,6 +455,7 @@ void __init setup_arch(char **cmdline_p)
 
 	mem_reserve(__pa(&_stext), __pa(&_end));
 
+#ifdef CONFIG_VECTORS_OFFSET
 	mem_reserve(__pa(&_WindowVectors_text_start),
 		    __pa(&_WindowVectors_text_end));
 
@@ -491,6 +492,8 @@ void __init setup_arch(char **cmdline_p)
 		    __pa(&_Level6InterruptVector_text_end));
 #endif
 
+#endif /* CONFIG_VECTORS_OFFSET */
+
 #ifdef CONFIG_SMP
 	mem_reserve(__pa(&_SecondaryResetVector_text_start),
 		    __pa(&_SecondaryResetVector_text_end));

arch/xtensa/kernel/vmlinux.lds.S

@@ -59,6 +59,7 @@ jiffies = jiffies_64;
  * garbage.)
  */
 
+#ifdef CONFIG_VECTORS_OFFSET
 #define SECTION_VECTOR(sym, section, addr, max_prevsec_size, prevsec)       \
   section addr : AT((MIN(LOADADDR(prevsec) + max_prevsec_size,		    \
 		         LOADADDR(prevsec) + SIZEOF(prevsec)) + 3) & ~ 3)   \
@@ -68,6 +69,11 @@ jiffies = jiffies_64;
     *(section)								    \
     sym ## _end = ABSOLUTE(.);						    \
   }
+#else
+#define SECTION_VECTOR(section, addr)					    \
+  . = addr;								    \
+  *(section)
+#endif
 
 /*
  *  Mapping of input sections to output sections when linking.
@@ -85,6 +91,37 @@ SECTIONS
   {
     /* The HEAD_TEXT section must be the first section! */
     HEAD_TEXT
+
+#ifndef CONFIG_VECTORS_OFFSET
+  . = ALIGN(PAGE_SIZE);
+  _vecbase = .;
+
+  SECTION_VECTOR (.WindowVectors.text, WINDOW_VECTORS_VADDR)
+#if XCHAL_EXCM_LEVEL >= 2
+  SECTION_VECTOR (.Level2InterruptVector.text, INTLEVEL2_VECTOR_VADDR)
+#endif
+#if XCHAL_EXCM_LEVEL >= 3
+  SECTION_VECTOR (.Level3InterruptVector.text, INTLEVEL3_VECTOR_VADDR)
+#endif
+#if XCHAL_EXCM_LEVEL >= 4
+  SECTION_VECTOR (.Level4InterruptVector.text, INTLEVEL4_VECTOR_VADDR)
+#endif
+#if XCHAL_EXCM_LEVEL >= 5
+  SECTION_VECTOR (.Level5InterruptVector.text, INTLEVEL5_VECTOR_VADDR)
+#endif
+#if XCHAL_EXCM_LEVEL >= 6
+  SECTION_VECTOR (.Level6InterruptVector.text, INTLEVEL6_VECTOR_VADDR)
+#endif
+  SECTION_VECTOR (.DebugInterruptVector.literal, DEBUG_VECTOR_VADDR - 4)
+  SECTION_VECTOR (.DebugInterruptVector.text, DEBUG_VECTOR_VADDR)
+  SECTION_VECTOR (.KernelExceptionVector.literal, KERNEL_VECTOR_VADDR - 4)
+  SECTION_VECTOR (.KernelExceptionVector.text, KERNEL_VECTOR_VADDR)
+  SECTION_VECTOR (.UserExceptionVector.literal, USER_VECTOR_VADDR - 4)
+  SECTION_VECTOR (.UserExceptionVector.text, USER_VECTOR_VADDR)
+  SECTION_VECTOR (.DoubleExceptionVector.literal, DOUBLEEXC_VECTOR_VADDR - 48)
+  SECTION_VECTOR (.DoubleExceptionVector.text, DOUBLEEXC_VECTOR_VADDR)
+#endif
+
     TEXT_TEXT
     VMLINUX_SYMBOL(__sched_text_start) = .;
     *(.sched.literal .sched.text)
@@ -132,6 +169,7 @@ SECTIONS
     . = ALIGN(16);
     __boot_reloc_table_start = ABSOLUTE(.);
 
+#ifdef CONFIG_VECTORS_OFFSET
     RELOCATE_ENTRY(_WindowVectors_text,
 		   .WindowVectors.text);
 #if XCHAL_EXCM_LEVEL >= 2
@@ -164,6 +202,7 @@ SECTIONS
 		   .DoubleExceptionVector.text);
     RELOCATE_ENTRY(_DebugInterruptVector_text,
 		   .DebugInterruptVector.text);
+#endif
 #if defined(CONFIG_SMP)
     RELOCATE_ENTRY(_SecondaryResetVector_text,
 		   .SecondaryResetVector.text);
@@ -186,6 +225,7 @@ SECTIONS
   . = ALIGN(4);
   .dummy : { LONG(0) }
 
+#ifdef CONFIG_VECTORS_OFFSET
   /* The vectors are relocated to the real position at startup time */
 
   SECTION_VECTOR (_WindowVectors_text,
@@ -277,6 +317,7 @@ SECTIONS
 
   . = (LOADADDR( .DoubleExceptionVector.text ) + SIZEOF( .DoubleExceptionVector.text ) + 3) & ~ 3;
 
+#endif
 #if defined(CONFIG_SMP)
 
   SECTION_VECTOR (_SecondaryResetVector_text,