xtensa: reorganize vectors placement

Allow vectors to be either merged into the kernel .text or put at a
fixed virtual address independently of XIP option. Drop option that
puts vectors at a fixed offset from the kernel text. Add choice to
Kconfig.
Vectors at fixed virtual address may be useful for XIP-aware MTD support
and for noMMU configurations with available IRAM. Configurations without
VECBASE register must put their vectors at specific locations regardless
of the selected option. All other configurations should happily use
merged vectors.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/Kconfig

@@ -572,15 +572,41 @@ config KERNEL_LOAD_ADDRESS
 
 	  If unsure, leave the default value here.
 
-config VECTORS_OFFSET
-	hex "Kernel vectors offset"
-	default 0x00003000
-	depends on !XIP_KERNEL
+choice
+	prompt "Relocatable vectors location"
+	default XTENSA_VECTORS_IN_TEXT
 	help
-	  This is the offset of the kernel image from the relocatable vectors
-	  base.
+	  Choose whether relocatable vectors are merged into the kernel .text
+	  or placed separately at runtime. This option does not affect
+	  configurations without VECBASE register where vectors are always
+	  placed at their hardware-defined locations.
 
-	  If unsure, leave the default value here.
+config XTENSA_VECTORS_IN_TEXT
+	bool "Merge relocatable vectors into kernel text"
+	depends on !MTD_XIP
+	help
+	  This option puts relocatable vectors into the kernel .text section
+	  with proper alignment.
+	  This is a safe choice for most configurations.
+
+config XTENSA_VECTORS_SEPARATE
+	bool "Put relocatable vectors at fixed address"
+	help
+	  This option puts relocatable vectors at specific virtual address.
+	  Vectors are merged with the .init data in the kernel image and
+	  are copied into their designated location during kernel startup.
+	  Use it to put vectors into IRAM or out of FLASH on kernels with
+	  XIP-aware MTD support.
+
+endchoice
+
+config VECTORS_ADDR
+	hex "Kernel vectors virtual address"
+	default 0x00000000
+	depends on XTENSA_VECTORS_SEPARATE
+	help
+	  This is the virtual address of the (relocatable) vectors base.
+	  It must be within KSEG if MMU is used.
 
 config XIP_DATA_ADDR
 	hex "XIP kernel data virtual address"

arch/xtensa/configs/smp_lx200_defconfig

@@ -30,7 +30,6 @@ CONFIG_SMP=y
 CONFIG_HOTPLUG_CPU=y
 # CONFIG_INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX is not set
 # CONFIG_PCI is not set
-CONFIG_VECTORS_OFFSET=0x00002000
 CONFIG_XTENSA_PLATFORM_XTFPGA=y
 CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE="earlycon=uart8250,mmio32native,0xfd050020,115200n8 console=ttyS0,115200n8 ip=dhcp root=/dev/nfs rw debug memmap=96M@0"

arch/xtensa/configs/virt_defconfig

@@ -19,7 +19,6 @@ CONFIG_KALLSYMS_ALL=y
 CONFIG_PERF_EVENTS=y
 CONFIG_XTENSA_VARIANT_DC233C=y
 CONFIG_XTENSA_UNALIGNED_USER=y
-CONFIG_VECTORS_OFFSET=0x00002000
 CONFIG_XTENSA_KSEG_512M=y
 CONFIG_HIGHMEM=y
 CONFIG_CMDLINE_BOOL=y

arch/xtensa/include/asm/vectors.h

@@ -34,8 +34,8 @@
 #endif
 
 #define RESET_VECTOR1_VADDR		(XCHAL_RESET_VECTOR1_VADDR)
-#ifdef CONFIG_VECTORS_OFFSET
-#define VECBASE_VADDR			(KERNELOFFSET - CONFIG_VECTORS_OFFSET)
+#ifdef CONFIG_VECTORS_ADDR
+#define VECBASE_VADDR			(CONFIG_VECTORS_ADDR)
 #else
 #define VECBASE_VADDR			_vecbase
 #endif

arch/xtensa/kernel/setup.c

@@ -349,7 +349,7 @@ void __init setup_arch(char **cmdline_p)
 	mem_reserve(__pa(_xip_start), __pa(_xip_end));
 #endif
 
-#ifdef CONFIG_VECTORS_OFFSET
+#ifdef CONFIG_VECTORS_ADDR
 	mem_reserve(__pa(&_WindowVectors_text_start),
 		    __pa(&_WindowVectors_text_end));
 
@@ -388,7 +388,7 @@ void __init setup_arch(char **cmdline_p)
 		    __pa(&_Level6InterruptVector_text_end));
 #endif
 
-#endif /* CONFIG_VECTORS_OFFSET */
+#endif /* CONFIG_VECTORS_ADDR */
 
 #ifdef CONFIG_SMP
 	mem_reserve(__pa(&_SecondaryResetVector_text_start),

arch/xtensa/kernel/vmlinux.lds.S

@@ -47,9 +47,15 @@ jiffies = jiffies_64;
 	LONG(sym ## _end);			\
 	LONG(LOADADDR(section))
 
+#if !defined(CONFIG_VECTORS_ADDR) && XCHAL_HAVE_VECBASE
+#define MERGED_VECTORS 1
+#else
+#define MERGED_VECTORS 0
+#endif
+
 /*
- * Macro to define a section for a vector. When CONFIG_VECTORS_OFFSET is
- * defined code for every vector is located with other init data. At startup
+ * Macro to define a section for a vector. When MERGED_VECTORS is 0
+ * code for every vector is located with other init data. At startup
  * time head.S copies code for every vector to its final position according
  * to description recorded in the corresponding RELOCATE_ENTRY.
  */
@@ -84,7 +90,7 @@ SECTIONS
     /* The HEAD_TEXT section must be the first section! */
     HEAD_TEXT
 
-#ifndef CONFIG_VECTORS_OFFSET
+#if MERGED_VECTORS
     . = ALIGN(PAGE_SIZE);
     _vecbase = .;
 
@@ -159,7 +165,7 @@ SECTIONS
     . = ALIGN(16);
     __boot_reloc_table_start = ABSOLUTE(.);
 
-#ifdef CONFIG_VECTORS_OFFSET
+#if !MERGED_VECTORS
     RELOCATE_ENTRY(_WindowVectors_text,
 		   .WindowVectors.text);
 #if XCHAL_EXCM_LEVEL >= 2
@@ -220,7 +226,7 @@ SECTIONS
 #undef LAST
 #define LAST	.dummy
 
-#ifdef CONFIG_VECTORS_OFFSET
+#if !MERGED_VECTORS
   /* The vectors are relocated to the real position at startup time */
 
   SECTION_VECTOR4 (_WindowVectors_text,
@@ -299,7 +305,7 @@ SECTIONS
 #define LAST .SecondaryResetVector.text
 
 #endif
-#ifdef CONFIG_VECTORS_OFFSET
+#if !MERGED_VECTORS
   SECTION_VECTOR4 (_exception_text,
 		  .exception.text,
 		  ,
@@ -310,6 +316,7 @@ SECTIONS
 #endif
   . = (LOADADDR(LAST) + SIZEOF(LAST) + 3) & ~ 3;
 
+  .dummy1 : AT(ADDR(.dummy1)) { LONG(0) }
   . = ALIGN(PAGE_SIZE);
 
 #ifndef CONFIG_XIP_KERNEL
@@ -327,7 +334,7 @@ SECTIONS
 
 #undef LOAD_OFFSET
 #define LOAD_OFFSET \
-  (CONFIG_XIP_DATA_ADDR - (LOADADDR(.dummy) + SIZEOF(.dummy) + 3) & ~ 3)
+  (CONFIG_XIP_DATA_ADDR - (LOADADDR(.dummy1) + SIZEOF(.dummy1) + 3) & ~ 3)
 
   _xip_data_start = .;
   _sdata = .;