diff options
author | Max Filippov | 2016-04-13 05:20:02 +0300 |
---|---|---|
committer | Max Filippov | 2016-07-24 06:33:58 +0300 |
commit | a9f2fc628e3a26a829fd79aff74eb49839d1e74b (patch) | |
tree | 7dad4e57c917757d39bb3470720392ac2b92b335 | |
parent | d39af90265feb40ec198c4ca8268724645b4b50e (diff) |
xtensa: cleanup MMU setup and kernel layout macros
Make kernel load address explicit, independent of the selected MMU
configuration and configurable from Kconfig. Do not restrict it to the
first 512MB of the physical address space.
Cleanup kernel memory layout macros:
- rename VECBASE_RESET_VADDR to VECBASE_VADDR, XC_VADDR to VECTOR_VADDR;
- drop VIRTUAL_MEMORY_ADDRESS and LOAD_MEMORY_ADDRESS;
- introduce PHYS_OFFSET and use it in __va and __pa definitions;
- synchronize MMU/noMMU vectors, drop unused NMI vector;
- replace hardcoded vectors offset of 0x3000 with Kconfig symbol.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
-rw-r--r-- | Documentation/xtensa/mmu.txt | 49 | ||||
-rw-r--r-- | arch/xtensa/Kconfig | 26 | ||||
-rw-r--r-- | arch/xtensa/boot/boot-elf/boot.lds.S | 2 | ||||
-rw-r--r-- | arch/xtensa/boot/boot-elf/bootstrap.S | 7 | ||||
-rw-r--r-- | arch/xtensa/boot/boot-uboot/Makefile | 10 | ||||
-rw-r--r-- | arch/xtensa/include/asm/initialize_mmu.h | 21 | ||||
-rw-r--r-- | arch/xtensa/include/asm/kmem_layout.h | 3 | ||||
-rw-r--r-- | arch/xtensa/include/asm/page.h | 8 | ||||
-rw-r--r-- | arch/xtensa/include/asm/vectors.h | 66 | ||||
-rw-r--r-- | arch/xtensa/kernel/entry.S | 5 | ||||
-rw-r--r-- | arch/xtensa/kernel/head.S | 2 | ||||
-rw-r--r-- | arch/xtensa/kernel/vmlinux.lds.S | 4 |
12 files changed, 98 insertions, 105 deletions
diff --git a/Documentation/xtensa/mmu.txt b/Documentation/xtensa/mmu.txt index 867c0f837e28..222a2c6748e6 100644 --- a/Documentation/xtensa/mmu.txt +++ b/Documentation/xtensa/mmu.txt @@ -3,15 +3,8 @@ MMUv3 initialization sequence. The code in the initialize_mmu macro sets up MMUv3 memory mapping identically to MMUv2 fixed memory mapping. Depending on CONFIG_INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX symbol this code is -located in one of the following address ranges: - - 0xF0000000..0xFFFFFFFF (will keep same address in MMU v2 layout; - typically ROM) - 0x00000000..0x07FFFFFF (system RAM; this code is actually linked - at 0xD0000000..0xD7FFFFFF [cached] - or 0xD8000000..0xDFFFFFFF [uncached]; - in any case, initially runs elsewhere - than linked, so have to be careful) +located in addresses it was linked for (symbol undefined), or not +(symbol defined), so it needs to be position-independent. The code has the following assumptions: This code fragment is run only on an MMU v3. @@ -28,24 +21,26 @@ TLB setup proceeds along the following steps. PA = physical address (two upper nibbles of it); pc = physical range that contains this code; -After step 2, we jump to virtual address in 0x40000000..0x5fffffff -that corresponds to next instruction to execute in this code. -After step 4, we jump to intended (linked) address of this code. - - Step 0 Step1 Step 2 Step3 Step 4 Step5 - ============ ===== ============ ===== ============ ===== - VA PA PA VA PA PA VA PA PA - ------ -- -- ------ -- -- ------ -- -- - E0..FF -> E0 -> E0 E0..FF -> E0 F0..FF -> F0 -> F0 - C0..DF -> C0 -> C0 C0..DF -> C0 E0..EF -> F0 -> F0 - A0..BF -> A0 -> A0 A0..BF -> A0 D8..DF -> 00 -> 00 - 80..9F -> 80 -> 80 80..9F -> 80 D0..D7 -> 00 -> 00 - 60..7F -> 60 -> 60 60..7F -> 60 - 40..5F -> 40 40..5F -> pc -> pc 40..5F -> pc - 20..3F -> 20 -> 20 20..3F -> 20 - 00..1F -> 00 -> 00 00..1F -> 00 - -The default location of IO peripherals is above 0xf0000000. This may change +After step 2, we jump to virtual address in the range 0x40000000..0x5fffffff +or 0x00000000..0x1fffffff, depending on whether the kernel was loaded below +0x40000000 or above. That address corresponds to next instruction to execute +in this code. After step 4, we jump to intended (linked) address of this code. +The scheme below assumes that the kernel is loaded below 0x40000000. + + Step0 Step1 Step2 Step3 Step4 Step5 + ===== ===== ===== ===== ===== ===== + VA PA PA PA PA VA PA PA + ------ -- -- -- -- ------ -- -- + E0..FF -> E0 -> E0 -> E0 F0..FF -> F0 -> F0 + C0..DF -> C0 -> C0 -> C0 E0..EF -> F0 -> F0 + A0..BF -> A0 -> A0 -> A0 D8..DF -> 00 -> 00 + 80..9F -> 80 -> 80 -> 80 D0..D7 -> 00 -> 00 + 60..7F -> 60 -> 60 -> 60 + 40..5F -> 40 -> pc -> pc 40..5F -> pc + 20..3F -> 20 -> 20 -> 20 + 00..1F -> 00 -> 00 -> 00 + +The default location of IO peripherals is above 0xf0000000. This may be changed using a "ranges" property in a device tree simple-bus node. See ePAPR 1.1, ยง6.5 for details on the syntax and semantic of simple-bus nodes. The following limitations apply: diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig index c17496bc37f0..9b1f8c3c8cba 100644 --- a/arch/xtensa/Kconfig +++ b/arch/xtensa/Kconfig @@ -249,6 +249,25 @@ config KSEG_PADDR If unsure, leave the default value here. +config KERNEL_LOAD_ADDRESS + hex "Kernel load address" + default 0x00003000 + help + This is the address where the kernel is loaded. + It is virtual address for MMUv2 configurations and physical address + for all other configurations. + + If unsure, leave the default value here. + +config VECTORS_OFFSET + hex "Kernel vectors offset" + default 0x00003000 + help + This is the offset of the kernel image from the relocatable vectors + base. + + If unsure, leave the default value here. + choice prompt "KSEG layout" depends on MMU @@ -487,12 +506,7 @@ config DEFAULT_MEM_START used when no physical memory size is passed through DTB or through boot parameter from bootloader. - In noMMU configuration the following parameters are derived from it: - - kernel load address; - - kernel entry point address; - - relocatable vectors base address; - - uBoot load address; - - TASK_SIZE. + It's also used for TASK_SIZE calculation in noMMU configuration. If unsure, leave the default value here. diff --git a/arch/xtensa/boot/boot-elf/boot.lds.S b/arch/xtensa/boot/boot-elf/boot.lds.S index e54f2c9df63a..a30993054e9c 100644 --- a/arch/xtensa/boot/boot-elf/boot.lds.S +++ b/arch/xtensa/boot/boot-elf/boot.lds.S @@ -23,7 +23,7 @@ SECTIONS *(.ResetVector.text) } - .image KERNELOFFSET: AT (LOAD_MEMORY_ADDRESS) + .image KERNELOFFSET: AT (CONFIG_KERNEL_LOAD_ADDRESS) { _image_start = .; *(image) diff --git a/arch/xtensa/boot/boot-elf/bootstrap.S b/arch/xtensa/boot/boot-elf/bootstrap.S index e6bf313613cf..b6aa85328ac0 100644 --- a/arch/xtensa/boot/boot-elf/bootstrap.S +++ b/arch/xtensa/boot/boot-elf/bootstrap.S @@ -35,7 +35,12 @@ _ResetVector: .align 4 RomInitAddr: - .word LOAD_MEMORY_ADDRESS +#if defined(CONFIG_INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX) && \ + XCHAL_HAVE_PTP_MMU && XCHAL_HAVE_SPANNING_WAY + .word CONFIG_KERNEL_LOAD_ADDRESS +#else + .word KERNELOFFSET +#endif RomBootParam: .word _bootparam _bootparam: diff --git a/arch/xtensa/boot/boot-uboot/Makefile b/arch/xtensa/boot/boot-uboot/Makefile index 403fcf23405c..0f4c417b4196 100644 --- a/arch/xtensa/boot/boot-uboot/Makefile +++ b/arch/xtensa/boot/boot-uboot/Makefile @@ -4,15 +4,7 @@ # for more details. # -ifdef CONFIG_MMU -ifdef CONFIG_INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX -UIMAGE_LOADADDR = 0x00003000 -else -UIMAGE_LOADADDR = 0xd0003000 -endif -else -UIMAGE_LOADADDR = $(shell printf "0x%x" $$(( ${CONFIG_DEFAULT_MEM_START} + 0x3000 )) ) -endif +UIMAGE_LOADADDR = $(CONFIG_KERNEL_LOAD_ADDRESS) UIMAGE_COMPRESSION = gzip $(obj)/../uImage: vmlinux.bin.gz FORCE diff --git a/arch/xtensa/include/asm/initialize_mmu.h b/arch/xtensa/include/asm/initialize_mmu.h index 46d4bef61655..42410f253597 100644 --- a/arch/xtensa/include/asm/initialize_mmu.h +++ b/arch/xtensa/include/asm/initialize_mmu.h @@ -77,13 +77,16 @@ .align 4 1: movi a2, 0x10000000 - movi a3, 0x18000000 - add a2, a2, a0 -9: bgeu a2, a3, 9b /* PC is out of the expected range */ + +#if CONFIG_KERNEL_LOAD_ADDRESS < 0x40000000ul +#define TEMP_MAPPING_VADDR 0x40000000 +#else +#define TEMP_MAPPING_VADDR 0x00000000 +#endif /* Step 1: invalidate mapping at 0x40000000..0x5FFFFFFF. */ - movi a2, 0x40000000 | XCHAL_SPANNING_WAY + movi a2, TEMP_MAPPING_VADDR | XCHAL_SPANNING_WAY idtlb a2 iitlb a2 isync @@ -95,14 +98,14 @@ srli a3, a0, 27 slli a3, a3, 27 addi a3, a3, CA_BYPASS - addi a7, a2, -1 + addi a7, a2, 5 - XCHAL_SPANNING_WAY wdtlb a3, a7 witlb a3, a7 isync slli a4, a0, 5 srli a4, a4, 5 - addi a5, a2, -6 + addi a5, a2, -XCHAL_SPANNING_WAY add a4, a4, a5 jx a4 @@ -145,19 +148,19 @@ witlb a4, a5 #endif - movi a5, XCHAL_KIO_CACHED_VADDR + 6 + movi a5, XCHAL_KIO_CACHED_VADDR + XCHAL_KIO_TLB_WAY movi a4, XCHAL_KIO_DEFAULT_PADDR + CA_WRITEBACK wdtlb a4, a5 witlb a4, a5 - movi a5, XCHAL_KIO_BYPASS_VADDR + 6 + movi a5, XCHAL_KIO_BYPASS_VADDR + XCHAL_KIO_TLB_WAY movi a4, XCHAL_KIO_DEFAULT_PADDR + CA_BYPASS wdtlb a4, a5 witlb a4, a5 isync - /* Jump to self, using MMU v2 mappings. */ + /* Jump to self, using final mappings. */ movi a4, 1f jx a4 diff --git a/arch/xtensa/include/asm/kmem_layout.h b/arch/xtensa/include/asm/kmem_layout.h index bfce7ee8efd8..561f8729bcde 100644 --- a/arch/xtensa/include/asm/kmem_layout.h +++ b/arch/xtensa/include/asm/kmem_layout.h @@ -29,6 +29,7 @@ #define XCHAL_KSEG_SIZE __XTENSA_UL_CONST(0x08000000) #define XCHAL_KSEG_ALIGNMENT __XTENSA_UL_CONST(0x08000000) #define XCHAL_KSEG_TLB_WAY 5 +#define XCHAL_KIO_TLB_WAY 6 #elif defined(CONFIG_XTENSA_KSEG_256M) @@ -37,6 +38,7 @@ #define XCHAL_KSEG_SIZE __XTENSA_UL_CONST(0x10000000) #define XCHAL_KSEG_ALIGNMENT __XTENSA_UL_CONST(0x10000000) #define XCHAL_KSEG_TLB_WAY 6 +#define XCHAL_KIO_TLB_WAY 6 #elif defined(CONFIG_XTENSA_KSEG_512M) @@ -45,6 +47,7 @@ #define XCHAL_KSEG_SIZE __XTENSA_UL_CONST(0x20000000) #define XCHAL_KSEG_ALIGNMENT __XTENSA_UL_CONST(0x10000000) #define XCHAL_KSEG_TLB_WAY 6 +#define XCHAL_KIO_TLB_WAY 6 #else #error Unsupported KSEG configuration diff --git a/arch/xtensa/include/asm/page.h b/arch/xtensa/include/asm/page.h index 8a02438232c4..3b5a49dbf8b2 100644 --- a/arch/xtensa/include/asm/page.h +++ b/arch/xtensa/include/asm/page.h @@ -27,10 +27,12 @@ #ifdef CONFIG_MMU #define PAGE_OFFSET XCHAL_KSEG_CACHED_VADDR +#define PHYS_OFFSET XCHAL_KSEG_PADDR #define MAX_LOW_PFN (PHYS_PFN(XCHAL_KSEG_PADDR) + \ PHYS_PFN(XCHAL_KSEG_SIZE)) #else #define PAGE_OFFSET __XTENSA_UL_CONST(0) +#define PHYS_OFFSET __XTENSA_UL_CONST(0) #define MAX_LOW_PFN (PHYS_PFN(PLATFORM_DEFAULT_MEM_START) + \ PHYS_PFN(PLATFORM_DEFAULT_MEM_SIZE)) #endif @@ -163,8 +165,10 @@ void copy_user_highpage(struct page *to, struct page *from, #define ARCH_PFN_OFFSET (PLATFORM_DEFAULT_MEM_START >> PAGE_SHIFT) -#define __pa(x) ((unsigned long) (x) - PAGE_OFFSET) -#define __va(x) ((void *)((unsigned long) (x) + PAGE_OFFSET)) +#define __pa(x) \ + ((unsigned long) (x) - PAGE_OFFSET + PHYS_OFFSET) +#define __va(x) \ + ((void *)((unsigned long) (x) - PHYS_OFFSET + PAGE_OFFSET)) #define pfn_valid(pfn) \ ((pfn) >= ARCH_PFN_OFFSET && ((pfn) - ARCH_PFN_OFFSET) < max_mapnr) diff --git a/arch/xtensa/include/asm/vectors.h b/arch/xtensa/include/asm/vectors.h index 482171051ff0..77d41cc7a688 100644 --- a/arch/xtensa/include/asm/vectors.h +++ b/arch/xtensa/include/asm/vectors.h @@ -48,61 +48,42 @@ static inline unsigned long xtensa_get_kio_paddr(void) #if defined(CONFIG_MMU) -/* Will Become VECBASE */ -#define VIRTUAL_MEMORY_ADDRESS XCHAL_KSEG_CACHED_VADDR - +#if XCHAL_HAVE_PTP_MMU && XCHAL_HAVE_SPANNING_WAY /* Image Virtual Start Address */ -#define KERNELOFFSET (XCHAL_KSEG_CACHED_VADDR + 0x3000) - -#if defined(XCHAL_HAVE_PTP_MMU) && XCHAL_HAVE_PTP_MMU && XCHAL_HAVE_SPANNING_WAY - /* MMU v3 - XCHAL_HAVE_PTP_MMU == 1 */ - #define LOAD_MEMORY_ADDRESS 0x00003000 +#define KERNELOFFSET (XCHAL_KSEG_CACHED_VADDR + \ + CONFIG_KERNEL_LOAD_ADDRESS - \ + XCHAL_KSEG_PADDR) #else - /* MMU V2 - XCHAL_HAVE_PTP_MMU == 0 */ - #define LOAD_MEMORY_ADDRESS 0xD0003000 +#define KERNELOFFSET CONFIG_KERNEL_LOAD_ADDRESS #endif -#define RESET_VECTOR1_VADDR (VIRTUAL_MEMORY_ADDRESS + \ - XCHAL_RESET_VECTOR1_PADDR) - #else /* !defined(CONFIG_MMU) */ /* MMU Not being used - Virtual == Physical */ - /* VECBASE */ - #define VIRTUAL_MEMORY_ADDRESS (PLATFORM_DEFAULT_MEM_START + 0x2000) +/* Location of the start of the kernel text, _start */ +#define KERNELOFFSET CONFIG_KERNEL_LOAD_ADDRESS - /* Location of the start of the kernel text, _start */ - #define KERNELOFFSET (PLATFORM_DEFAULT_MEM_START + 0x3000) - - /* Loaded just above possibly live vectors */ - #define LOAD_MEMORY_ADDRESS (PLATFORM_DEFAULT_MEM_START + 0x3000) - -#define RESET_VECTOR1_VADDR (XCHAL_RESET_VECTOR1_VADDR) #endif /* CONFIG_MMU */ -#define XC_VADDR(offset) (VIRTUAL_MEMORY_ADDRESS + offset) - -/* Used to set VECBASE register */ -#define VECBASE_RESET_VADDR VIRTUAL_MEMORY_ADDRESS +#define RESET_VECTOR1_VADDR (XCHAL_RESET_VECTOR1_VADDR) +#define VECBASE_VADDR (KERNELOFFSET - CONFIG_VECTORS_OFFSET) #if defined(XCHAL_HAVE_VECBASE) && XCHAL_HAVE_VECBASE -#define USER_VECTOR_VADDR XC_VADDR(XCHAL_USER_VECOFS) -#define KERNEL_VECTOR_VADDR XC_VADDR(XCHAL_KERNEL_VECOFS) -#define DOUBLEEXC_VECTOR_VADDR XC_VADDR(XCHAL_DOUBLEEXC_VECOFS) -#define WINDOW_VECTORS_VADDR XC_VADDR(XCHAL_WINDOW_OF4_VECOFS) -#define INTLEVEL2_VECTOR_VADDR XC_VADDR(XCHAL_INTLEVEL2_VECOFS) -#define INTLEVEL3_VECTOR_VADDR XC_VADDR(XCHAL_INTLEVEL3_VECOFS) -#define INTLEVEL4_VECTOR_VADDR XC_VADDR(XCHAL_INTLEVEL4_VECOFS) -#define INTLEVEL5_VECTOR_VADDR XC_VADDR(XCHAL_INTLEVEL5_VECOFS) -#define INTLEVEL6_VECTOR_VADDR XC_VADDR(XCHAL_INTLEVEL6_VECOFS) - -#define DEBUG_VECTOR_VADDR XC_VADDR(XCHAL_DEBUG_VECOFS) +#define VECTOR_VADDR(offset) (VECBASE_VADDR + offset) -#define NMI_VECTOR_VADDR XC_VADDR(XCHAL_NMI_VECOFS) - -#define INTLEVEL7_VECTOR_VADDR XC_VADDR(XCHAL_INTLEVEL7_VECOFS) +#define USER_VECTOR_VADDR VECTOR_VADDR(XCHAL_USER_VECOFS) +#define KERNEL_VECTOR_VADDR VECTOR_VADDR(XCHAL_KERNEL_VECOFS) +#define DOUBLEEXC_VECTOR_VADDR VECTOR_VADDR(XCHAL_DOUBLEEXC_VECOFS) +#define WINDOW_VECTORS_VADDR VECTOR_VADDR(XCHAL_WINDOW_OF4_VECOFS) +#define INTLEVEL2_VECTOR_VADDR VECTOR_VADDR(XCHAL_INTLEVEL2_VECOFS) +#define INTLEVEL3_VECTOR_VADDR VECTOR_VADDR(XCHAL_INTLEVEL3_VECOFS) +#define INTLEVEL4_VECTOR_VADDR VECTOR_VADDR(XCHAL_INTLEVEL4_VECOFS) +#define INTLEVEL5_VECTOR_VADDR VECTOR_VADDR(XCHAL_INTLEVEL5_VECOFS) +#define INTLEVEL6_VECTOR_VADDR VECTOR_VADDR(XCHAL_INTLEVEL6_VECOFS) +#define INTLEVEL7_VECTOR_VADDR VECTOR_VADDR(XCHAL_INTLEVEL7_VECOFS) +#define DEBUG_VECTOR_VADDR VECTOR_VADDR(XCHAL_DEBUG_VECOFS) /* * These XCHAL_* #defines from varian/core.h @@ -110,7 +91,6 @@ static inline unsigned long xtensa_get_kio_paddr(void) * constants are defined above and should be used. */ #undef XCHAL_VECBASE_RESET_VADDR -#undef XCHAL_RESET_VECTOR0_VADDR #undef XCHAL_USER_VECTOR_VADDR #undef XCHAL_KERNEL_VECTOR_VADDR #undef XCHAL_DOUBLEEXC_VECTOR_VADDR @@ -120,9 +100,8 @@ static inline unsigned long xtensa_get_kio_paddr(void) #undef XCHAL_INTLEVEL4_VECTOR_VADDR #undef XCHAL_INTLEVEL5_VECTOR_VADDR #undef XCHAL_INTLEVEL6_VECTOR_VADDR -#undef XCHAL_DEBUG_VECTOR_VADDR -#undef XCHAL_NMI_VECTOR_VADDR #undef XCHAL_INTLEVEL7_VECTOR_VADDR +#undef XCHAL_DEBUG_VECTOR_VADDR #else @@ -135,6 +114,7 @@ static inline unsigned long xtensa_get_kio_paddr(void) #define INTLEVEL4_VECTOR_VADDR XCHAL_INTLEVEL4_VECTOR_VADDR #define INTLEVEL5_VECTOR_VADDR XCHAL_INTLEVEL5_VECTOR_VADDR #define INTLEVEL6_VECTOR_VADDR XCHAL_INTLEVEL6_VECTOR_VADDR +#define INTLEVEL7_VECTOR_VADDR XCHAL_INTLEVEL6_VECTOR_VADDR #define DEBUG_VECTOR_VADDR XCHAL_DEBUG_VECTOR_VADDR #endif diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S index fe8f7e7efb9d..fa04d9d368a7 100644 --- a/arch/xtensa/kernel/entry.S +++ b/arch/xtensa/kernel/entry.S @@ -1632,10 +1632,11 @@ ENTRY(fast_second_level_miss) * The messy computation for 'pteval' above really simplifies * into the following: * - * pteval = ((pmdval - PAGE_OFFSET) & PAGE_MASK) | PAGE_DIRECTORY + * pteval = ((pmdval - PAGE_OFFSET + PHYS_OFFSET) & PAGE_MASK) + * | PAGE_DIRECTORY */ - movi a1, (-PAGE_OFFSET) & 0xffffffff + movi a1, (PHYS_OFFSET - PAGE_OFFSET) & 0xffffffff add a0, a0, a1 # pmdval - PAGE_OFFSET extui a1, a0, 0, PAGE_SHIFT # ... & PAGE_MASK xor a0, a0, a1 diff --git a/arch/xtensa/kernel/head.S b/arch/xtensa/kernel/head.S index bc4f4bf05099..23ce62e60435 100644 --- a/arch/xtensa/kernel/head.S +++ b/arch/xtensa/kernel/head.S @@ -113,7 +113,7 @@ ENTRY(_startup) movi a0, 0 #if XCHAL_HAVE_VECBASE - movi a2, VECBASE_RESET_VADDR + movi a2, VECBASE_VADDR wsr a2, vecbase #endif diff --git a/arch/xtensa/kernel/vmlinux.lds.S b/arch/xtensa/kernel/vmlinux.lds.S index c417cbe4ec87..72cfe3587dd8 100644 --- a/arch/xtensa/kernel/vmlinux.lds.S +++ b/arch/xtensa/kernel/vmlinux.lds.S @@ -30,10 +30,6 @@ jiffies = jiffies_64 + 4; jiffies = jiffies_64; #endif -#ifndef KERNELOFFSET -#define KERNELOFFSET 0xd0003000 -#endif - /* Note: In the following macros, it would be nice to specify only the vector name and section kind and construct "sym" and "section" using CPP concatenation, but that does not work reliably. Concatenating a |