Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 29 Mar 2021 23:23:04 -0700 (PDT)
Subject:     Re: [PATCH v6] RISC-V: enable XIP
In-Reply-To: <20210322001214.29985-1-vitaly.wool@konsulko.com>
CC:     linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        bin.meng@windriver.com, anup@brainfault.org,
        Alistair Francis <Alistair.Francis@wdc.com>, nico@fluxnic.net,
        alex@ghiti.fr, vitaly.wool@konsulko.com
From:   Palmer Dabbelt <palmerdabbelt@google.com>
To:     vitaly.wool@konsulko.com
Message-ID: <mhng-5c1edc6a-c0fc-4556-9aef-b2b330856f99@palmerdabbelt-glaptop>
Mime-Version: 1.0 (MHng)
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

On Sun, 21 Mar 2021 17:12:15 PDT (-0700), vitaly.wool@konsulko.com wrote:
> Introduce XIP (eXecute In Place) support for RISC-V platforms.
> It allows code to be executed directly from non-volatile storage
> directly addressable by the CPU, such as QSPI NOR flash which can
> be found on many RISC-V platforms. This makes way for significant
> optimization of RAM footprint. The XIP kernel is not compressed
> since it has to run directly from flash, so it will occupy more
> space on the non-volatile storage. The physical flash address used
> to link the kernel object files and for storing it has to be known
> at compile time and is represented by a Kconfig option.
>
> XIP on RISC-V will for the time being only work on MMU-enabled
> kernels.
>
> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
>
> ---
>
> Changes in v2:
> - dedicated macro for XIP address fixup when MMU is not enabled yet
>   o both for 32-bit and 64-bit RISC-V
> - SP is explicitly set to a safe place in RAM before __copy_data call
> - removed redundant alignment requirements in vmlinux-xip.lds.S
> - changed long -> uintptr_t typecast in __XIP_FIXUP macro.
> Changes in v3:
> - rebased against latest for-next
> - XIP address fixup macro now takes an argument
> - SMP related fixes
> Changes in v4:
> - rebased against the current for-next
> - less #ifdef's in C/ASM code
> - dedicated XIP_FIXUP_OFFSET assembler macro in head.S
> - C-specific definitions moved into #ifndef __ASSEMBLY__
> - Fixed multi-core boot
> Changes in v5:
> - fixed build error for non-XIP kernels
> Changes in v6:
> - XIP_PHYS_RAM_BASE config option renamed to PHYS_RAM_BASE
> - added PHYS_RAM_BASE_FIXED config flag to allow usage of
>   PHYS_RAM_BASE in non-XIP configurations if needed
> - XIP_FIXUP macro rewritten with a tempoarary variable to avoid side
>   effects
> - fixed crash for non-XIP kernels that don't use built-in DTB

So v5 landed on for-next, which generally means it's best to avoid 
re-spinning the patch and instead send along fixups.  That said, the v5 
is causing some testing failures for me.

I'm going to drop the v5 for now as I don't have time to test this 
tonight.  I'll try and take a look soon, as it will conflict with Alex's 
patches.

>  arch/riscv/Kconfig                  |  49 ++++++++++-
>  arch/riscv/Makefile                 |   8 +-
>  arch/riscv/boot/Makefile            |  13 +++
>  arch/riscv/include/asm/pgtable.h    |  65 ++++++++++++--
>  arch/riscv/kernel/cpu_ops_sbi.c     |  11 ++-
>  arch/riscv/kernel/head.S            |  49 ++++++++++-
>  arch/riscv/kernel/head.h            |   3 +
>  arch/riscv/kernel/setup.c           |   8 +-
>  arch/riscv/kernel/vmlinux-xip.lds.S | 132 ++++++++++++++++++++++++++++
>  arch/riscv/kernel/vmlinux.lds.S     |   6 ++
>  arch/riscv/mm/init.c                | 100 +++++++++++++++++++--
>  11 files changed, 426 insertions(+), 18 deletions(-)
>  create mode 100644 arch/riscv/kernel/vmlinux-xip.lds.S
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 8ea60a0a19ae..bd6f82240c34 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -441,7 +441,7 @@ config EFI_STUB
>
>  config EFI
>  	bool "UEFI runtime support"
> -	depends on OF
> +	depends on OF && !XIP_KERNEL
>  	select LIBFDT
>  	select UCS2_STRING
>  	select EFI_PARAMS_FROM_FDT
> @@ -465,11 +465,56 @@ config STACKPROTECTOR_PER_TASK
>  	def_bool y
>  	depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_TLS
>
> +config PHYS_RAM_BASE_FIXED
> +	bool "Explicitly specified physical RAM address"
> +	default n
> +
> +config PHYS_RAM_BASE
> +	hex "Platform Physical RAM address"
> +	depends on PHYS_RAM_BASE_FIXED
> +	default "0x80000000"
> +	help
> +	  This is the physical address of RAM in the system. It has to be
> +	  explicitly specified to run early relocations of read-write data
> +	  from flash to RAM.
> +
> +config XIP_KERNEL
> +	bool "Kernel Execute-In-Place from ROM"
> +	depends on MMU
> +	select PHYS_RAM_BASE_FIXED
> +	help
> +	  Execute-In-Place allows the kernel to run from non-volatile storage
> +	  directly addressable by the CPU, such as NOR flash. This saves RAM
> +	  space since the text section of the kernel is not loaded from flash
> +	  to RAM.  Read-write sections, such as the data section and stack,
> +	  are still copied to RAM.  The XIP kernel is not compressed since
> +	  it has to run directly from flash, so it will take more space to
> +	  store it.  The flash address used to link the kernel object files,
> +	  and for storing it, is configuration dependent. Therefore, if you
> +	  say Y here, you must know the proper physical address where to
> +	  store the kernel image depending on your own flash memory usage.
> +
> +	  Also note that the make target becomes "make xipImage" rather than
> +	  "make zImage" or "make Image".  The final kernel binary to put in
> +	  ROM memory will be arch/riscv/boot/xipImage.
> +
> +	  If unsure, say N.
> +
> +config XIP_PHYS_ADDR
> +	hex "XIP Kernel Physical Location"
> +	depends on XIP_KERNEL
> +	default "0x21000000"
> +	help
> +	  This is the physical address in your flash memory the kernel will
> +	  be linked for and stored to.  This address is dependent on your
> +	  own flash usage.
> +
>  endmenu
>
>  config BUILTIN_DTB
> -	def_bool n
> +	bool
>  	depends on OF
> +	default y if XIP_KERNEL
>
>  menu "Power management options"
>
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index 1368d943f1f3..8fcbec03974d 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -82,7 +82,11 @@ CHECKFLAGS += -D__riscv -D__riscv_xlen=$(BITS)
>
>  # Default target when executing plain make
>  boot		:= arch/riscv/boot
> +ifeq ($(CONFIG_XIP_KERNEL),y)
> +KBUILD_IMAGE := $(boot)/xipImage
> +else
>  KBUILD_IMAGE	:= $(boot)/Image.gz
> +endif
>
>  head-y := arch/riscv/kernel/head.o
>
> @@ -95,12 +99,14 @@ PHONY += vdso_install
>  vdso_install:
>  	$(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
>
> +ifneq ($(CONFIG_XIP_KERNEL),y)
>  ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN),yy)
>  KBUILD_IMAGE := $(boot)/loader.bin
>  else
>  KBUILD_IMAGE := $(boot)/Image.gz
>  endif
> -BOOT_TARGETS := Image Image.gz loader loader.bin
> +endif
> +BOOT_TARGETS := Image Image.gz loader loader.bin xipImage
>
>  all:	$(notdir $(KBUILD_IMAGE))
>
> diff --git a/arch/riscv/boot/Makefile b/arch/riscv/boot/Makefile
> index 03404c84f971..6bf299f70c27 100644
> --- a/arch/riscv/boot/Makefile
> +++ b/arch/riscv/boot/Makefile
> @@ -17,8 +17,21 @@
>  KCOV_INSTRUMENT := n
>
>  OBJCOPYFLAGS_Image :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
> +OBJCOPYFLAGS_xipImage :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
>
>  targets := Image Image.* loader loader.o loader.lds loader.bin
> +targets := Image Image.* loader loader.o loader.lds loader.bin xipImage
> +
> +ifeq ($(CONFIG_XIP_KERNEL),y)
> +
> +quiet_cmd_mkxip = $(quiet_cmd_objcopy)
> +cmd_mkxip = $(cmd_objcopy)
> +
> +$(obj)/xipImage: vmlinux FORCE
> +	$(call if_changed,mkxip)
> +	@$(kecho) '  Physical Address of xipImage: $(CONFIG_XIP_PHYS_ADDR)'
> +
> +endif
>
>  $(obj)/Image: vmlinux FORCE
>  	$(call if_changed,objcopy)
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index ebf817c1bdf4..21a9b2f8d1c7 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -11,6 +11,33 @@
>
>  #include <asm/pgtable-bits.h>
>
> +#ifdef CONFIG_MMU
> +
> +#define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
> +
> +#ifdef CONFIG_XIP_KERNEL
> +#define VMALLOC_SIZE     ((KERN_VIRT_SIZE >> 1) - SZ_16M)
> +#define VMALLOC_END      (PAGE_OFFSET - SZ_16M - 1)
> +
> +#define XIP_OFFSET		SZ_8M
> +#define XIP_MASK		(SZ_8M - 1)
> +#define XIP_VIRT_ADDR(physaddr)	\
> +	(PAGE_OFFSET - XIP_OFFSET + ((physaddr) & XIP_MASK))
> +
> +#else
> +
> +#define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
> +#define VMALLOC_END      (PAGE_OFFSET - 1)
> +
> +#endif /* CONFIG_XIP_KERNEL */
> +
> +#else
> +
> +#ifdef CONFIG_XIP_KERNEL
> +#define XIP_VIRT_ADDR(physaddr) (physaddr)
> +#endif /* CONFIG_XIP_KERNEL */
> +#endif /* CONFIG_MMU */
> +
>  #ifndef __ASSEMBLY__
>
>  /* Page Upper Directory not used in RISC-V */
> @@ -21,9 +48,25 @@
>
>  #ifdef CONFIG_MMU
>
> -#define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
> -#define VMALLOC_END      (PAGE_OFFSET - 1)
> -#define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
> +#ifdef CONFIG_XIP_KERNEL
> +/*
> + * Since we use sections to map it, this macro replaces the physical address
> + * with its virtual address while keeping offset from the base section.
> + */
> +#define XIP_PHYS_ADDR(va)	 \
> +	((uintptr_t)(va) - PAGE_OFFSET + XIP_OFFSET + CONFIG_XIP_PHYS_ADDR)
> +
> +#define XIP_VIRT_ADDR_START	XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
> +
> +#define XIP_FIXUP(addr)		({ \
> +	uintptr_t __a = (uintptr_t)(addr); \
> +	(__a >= CONFIG_XIP_PHYS_ADDR && \
> +	 __a < CONFIG_XIP_PHYS_ADDR + SZ_16M) ? \
> +	__a - CONFIG_XIP_PHYS_ADDR + CONFIG_PHYS_RAM_BASE - XIP_OFFSET : __a; \
> +})
> +#else
> +#define XIP_FIXUP(addr)		(addr)
> +#endif /* CONFIG_XIP_KERNEL */
>
>  #define BPF_JIT_REGION_SIZE	(SZ_128M)
>  #define BPF_JIT_REGION_START	(PAGE_OFFSET - BPF_JIT_REGION_SIZE)
> @@ -484,8 +527,20 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
>
>  #define kern_addr_valid(addr)   (1) /* FIXME */
>
> -extern void *dtb_early_va;
> -extern uintptr_t dtb_early_pa;
> +extern void *_dtb_early_va;
> +extern uintptr_t _dtb_early_pa;
> +#if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_MMU)
> +
> +#define dtb_early_va	(*(void **)XIP_FIXUP(&_dtb_early_va))
> +#define dtb_early_pa	(*(uintptr_t *)XIP_FIXUP(&_dtb_early_pa))
> +
> +#else
> +
> +#define dtb_early_va	_dtb_early_va
> +#define dtb_early_pa	_dtb_early_pa
> +
> +#endif /* CONFIG_XIP_KERNEL */
> +
>  void setup_bootmem(void);
>  void paging_init(void);
>  void misc_mem_init(void);
> diff --git a/arch/riscv/kernel/cpu_ops_sbi.c b/arch/riscv/kernel/cpu_ops_sbi.c
> index 685fae72b7f5..2413c2997350 100644
> --- a/arch/riscv/kernel/cpu_ops_sbi.c
> +++ b/arch/riscv/kernel/cpu_ops_sbi.c
> @@ -53,10 +53,19 @@ static int sbi_hsm_hart_get_status(unsigned long hartid)
>  }
>  #endif
>
> +static inline unsigned long get_secondary_start_phys(void)
> +{
> +#ifdef CONFIG_XIP_KERNEL
> +	return XIP_PHYS_ADDR(secondary_start_sbi);
> +#else
> +	return __pa_symbol(secondary_start_sbi);
> +#endif
> +}
> +
>  static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle)
>  {
>  	int rc;
> -	unsigned long boot_addr = __pa_symbol(secondary_start_sbi);
> +	unsigned long boot_addr = get_secondary_start_phys();
>  	int hartid = cpuid_to_hartid_map(cpuid);
>
>  	cpu_update_secondary_bootdata(cpuid, tidle);
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index f5a9bad86e58..bbe74e37914f 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -9,11 +9,23 @@
>  #include <linux/linkage.h>
>  #include <asm/thread_info.h>
>  #include <asm/page.h>
> +#include <asm/pgtable.h>
>  #include <asm/csr.h>
>  #include <asm/hwcap.h>
>  #include <asm/image.h>
>  #include "efi-header.S"
>
> +#ifdef CONFIG_XIP_KERNEL
> +.macro XIP_FIXUP_OFFSET reg
> +	REG_L t0, _xip_fixup
> +	add \reg, \reg, t0
> +.endm
> +_xip_fixup: .dword CONFIG_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR - XIP_OFFSET
> +#else
> +.macro XIP_FIXUP_OFFSET reg
> +.endm
> +#endif /* CONFIG_XIP_KERNEL */
> +
>  __HEAD
>  ENTRY(_start)
>  	/*
> @@ -69,7 +81,11 @@ pe_head_start:
>  #ifdef CONFIG_MMU
>  relocate:
>  	/* Relocate return address */
> +#ifdef CONFIG_XIP_KERNEL
> +	li a1, XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
> +#else
>  	li a1, PAGE_OFFSET
> +#endif
>  	la a2, _start
>  	sub a1, a1, a2
>  	add ra, ra, a1
> @@ -91,6 +107,7 @@ relocate:
>  	 * to ensure the new translations are in use.
>  	 */
>  	la a0, trampoline_pg_dir
> +	XIP_FIXUP_OFFSET a0
>  	srl a0, a0, PAGE_SHIFT
>  	or a0, a0, a1
>  	sfence.vma
> @@ -144,7 +161,9 @@ secondary_start_sbi:
>
>  	slli a3, a0, LGREG
>  	la a4, __cpu_up_stack_pointer
> +	XIP_FIXUP_OFFSET a4
>  	la a5, __cpu_up_task_pointer
> +	XIP_FIXUP_OFFSET a5
>  	add a4, a3, a4
>  	add a5, a3, a5
>  	REG_L sp, (a4)
> @@ -156,6 +175,7 @@ secondary_start_common:
>  #ifdef CONFIG_MMU
>  	/* Enable virtual memory and relocate to virtual address */
>  	la a0, swapper_pg_dir
> +	XIP_FIXUP_OFFSET a0
>  	call relocate
>  #endif
>  	call setup_trap_vector
> @@ -236,12 +256,33 @@ pmp_done:
>  .Lgood_cores:
>  #endif
>
> +#ifndef CONFIG_XIP_KERNEL
>  	/* Pick one hart to run the main boot sequence */
>  	la a3, hart_lottery
>  	li a2, 1
>  	amoadd.w a3, a2, (a3)
>  	bnez a3, .Lsecondary_start
>
> +#else
> +	/* hart_lottery in flash contains a magic number */
> +	la a3, hart_lottery
> +	mv a2, a3
> +	XIP_FIXUP_OFFSET a2
> +	lw t1, (a3)
> +	amoswap.w t0, t1, (a2)
> +	/* first time here if hart_lottery in RAM is not set */
> +	beq t0, t1, .Lsecondary_start
> +
> +	la sp, _end + THREAD_SIZE
> +	XIP_FIXUP_OFFSET sp
> +	mv s0, a0
> +	call __copy_data
> +
> +	/* Restore a0 copy */
> +	mv a0, s0
> +#endif
> +
> +#ifndef CONFIG_XIP_KERNEL
>  	/* Clear BSS for flat non-ELF images */
>  	la a3, __bss_start
>  	la a4, __bss_stop
> @@ -251,15 +292,18 @@ clear_bss:
>  	add a3, a3, RISCV_SZPTR
>  	blt a3, a4, clear_bss
>  clear_bss_done:
> -
> +#endif
>  	/* Save hart ID and DTB physical address */
>  	mv s0, a0
>  	mv s1, a1
> +
>  	la a2, boot_cpu_hartid
> +	XIP_FIXUP_OFFSET a2
>  	REG_S a0, (a2)
>
>  	/* Initialize page tables and relocate to virtual addresses */
>  	la sp, init_thread_union + THREAD_SIZE
> +	XIP_FIXUP_OFFSET sp
>  #ifdef CONFIG_BUILTIN_DTB
>  	la a0, __dtb_start
>  #else
> @@ -268,6 +312,7 @@ clear_bss_done:
>  	call setup_vm
>  #ifdef CONFIG_MMU
>  	la a0, early_pg_dir
> +	XIP_FIXUP_OFFSET a0
>  	call relocate
>  #endif /* CONFIG_MMU */
>
> @@ -292,7 +337,9 @@ clear_bss_done:
>
>  	slli a3, a0, LGREG
>  	la a1, __cpu_up_stack_pointer
> +	XIP_FIXUP_OFFSET a1
>  	la a2, __cpu_up_task_pointer
> +	XIP_FIXUP_OFFSET a2
>  	add a1, a3, a1
>  	add a2, a3, a2
>
> diff --git a/arch/riscv/kernel/head.h b/arch/riscv/kernel/head.h
> index b48dda3d04f6..aabbc3ac3e48 100644
> --- a/arch/riscv/kernel/head.h
> +++ b/arch/riscv/kernel/head.h
> @@ -12,6 +12,9 @@ extern atomic_t hart_lottery;
>
>  asmlinkage void do_page_fault(struct pt_regs *regs);
>  asmlinkage void __init setup_vm(uintptr_t dtb_pa);
> +#ifdef CONFIG_XIP_KERNEL
> +asmlinkage void __init __copy_data(void);
> +#endif
>
>  extern void *__cpu_up_stack_pointer[];
>  extern void *__cpu_up_task_pointer[];
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index e85bacff1b50..a0384c72c272 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -50,7 +50,11 @@ struct screen_info screen_info __section(".data") = {
>   * This is used before the kernel initializes the BSS so it can't be in the
>   * BSS.
>   */
> -atomic_t hart_lottery __section(".sdata");
> +atomic_t hart_lottery __section(".sdata")
> +#ifdef CONFIG_XIP_KERNEL
> += ATOMIC_INIT(0xC001BEEF)
> +#endif
> +;
>  unsigned long boot_cpu_hartid;
>  static DEFINE_PER_CPU(struct cpu, cpu_devices);
>
> @@ -254,7 +258,7 @@ void __init setup_arch(char **cmdline_p)
>  #if IS_ENABLED(CONFIG_BUILTIN_DTB)
>  	unflatten_and_copy_device_tree();
>  #else
> -	if (early_init_dt_verify(__va(dtb_early_pa)))
> +	if (early_init_dt_verify(__va(XIP_FIXUP(dtb_early_pa))))
>  		unflatten_device_tree();
>  	else
>  		pr_err("No DTB found in kernel mappings\n");
> diff --git a/arch/riscv/kernel/vmlinux-xip.lds.S b/arch/riscv/kernel/vmlinux-xip.lds.S
> new file mode 100644
> index 000000000000..9f0f08c34cd3
> --- /dev/null
> +++ b/arch/riscv/kernel/vmlinux-xip.lds.S
> @@ -0,0 +1,132 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2012 Regents of the University of California
> + * Copyright (C) 2017 SiFive
> + * Copyright (C) 2020 Vitaly Wool, Konsulko AB
> + */
> +
> +#define LOAD_OFFSET XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
> +/* No __ro_after_init data in the .rodata section - which will always be ro */
> +#define RO_AFTER_INIT_DATA
> +
> +#include <asm/vmlinux.lds.h>
> +#include <asm/page.h>
> +#include <asm/pgtable.h>
> +#include <asm/cache.h>
> +#include <asm/thread_info.h>
> +
> +OUTPUT_ARCH(riscv)
> +ENTRY(_start)
> +
> +jiffies = jiffies_64;
> +
> +SECTIONS
> +{
> +	/* Beginning of code and text segment */
> +	. = XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR);
> +	_xiprom = .;
> +	_start = .;
> +	HEAD_TEXT_SECTION
> +	INIT_TEXT_SECTION(PAGE_SIZE)
> +	/* we have to discard exit text and such at runtime, not link time */
> +	.exit.text :
> +	{
> +		EXIT_TEXT
> +	}
> +
> +	.text : {
> +		_text = .;
> +		_stext = .;
> +		TEXT_TEXT
> +		SCHED_TEXT
> +		CPUIDLE_TEXT
> +		LOCK_TEXT
> +		KPROBES_TEXT
> +		ENTRY_TEXT
> +		IRQENTRY_TEXT
> +		SOFTIRQENTRY_TEXT
> +		*(.fixup)
> +		_etext = .;
> +	}
> +	RO_DATA(L1_CACHE_BYTES)
> +	.srodata : {
> +		*(.srodata*)
> +	}
> +	.init.rodata : {
> +		INIT_SETUP(16)
> +		INIT_CALLS
> +		CON_INITCALL
> +		INIT_RAM_FS
> +	}
> +	_exiprom = .;			/* End of XIP ROM area */
> +
> +
> +/*
> + * From this point, stuff is considered writable and will be copied to RAM
> + */
> +	__data_loc = ALIGN(16);		/* location in file */
> +	. = PAGE_OFFSET;		/* location in memory */
> +
> +	_sdata = .;			/* Start of data section */
> +	_data = .;
> +	RW_DATA(L1_CACHE_BYTES, PAGE_SIZE, THREAD_SIZE)
> +	_edata = .;
> +	__start_ro_after_init = .;
> +	.data.ro_after_init : AT(ADDR(.data.ro_after_init) - LOAD_OFFSET) {
> +		*(.data..ro_after_init)
> +	}
> +	__end_ro_after_init = .;
> +
> +	. = ALIGN(PAGE_SIZE);
> +	__init_begin = .;
> +	.init.data : {
> +		INIT_DATA
> +	}
> +	.exit.data : {
> +		EXIT_DATA
> +	}
> +	. = ALIGN(8);
> +	__soc_early_init_table : {
> +		__soc_early_init_table_start = .;
> +		KEEP(*(__soc_early_init_table))
> +		__soc_early_init_table_end = .;
> +	}
> +	__soc_builtin_dtb_table : {
> +		__soc_builtin_dtb_table_start = .;
> +		KEEP(*(__soc_builtin_dtb_table))
> +		__soc_builtin_dtb_table_end = .;
> +	}
> +	PERCPU_SECTION(L1_CACHE_BYTES)
> +
> +	. = ALIGN(PAGE_SIZE);
> +	__init_end = .;
> +
> +	.sdata : {
> +		__global_pointer$ = . + 0x800;
> +		*(.sdata*)
> +		*(.sbss*)
> +	}
> +
> +	BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
> +	EXCEPTION_TABLE(0x10)
> +
> +	.rel.dyn : AT(ADDR(.rel.dyn) - LOAD_OFFSET) {
> +		*(.rel.dyn*)
> +	}
> +
> +	/*
> +	 * End of copied data. We need a dummy section to get its LMA.
> +	 * Also located before final ALIGN() as trailing padding is not stored
> +	 * in the resulting binary file and useless to copy.
> +	 */
> +	.data.endmark : AT(ADDR(.data.endmark) - LOAD_OFFSET) { }
> +	_edata_loc = LOADADDR(.data.endmark);
> +
> +	. = ALIGN(PAGE_SIZE);
> +	_end = .;
> +
> +	STABS_DEBUG
> +	DWARF_DEBUG
> +
> +	DISCARDS
> +}
> diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
> index de03cb22d0e9..6745ec325930 100644
> --- a/arch/riscv/kernel/vmlinux.lds.S
> +++ b/arch/riscv/kernel/vmlinux.lds.S
> @@ -4,7 +4,12 @@
>   * Copyright (C) 2017 SiFive
>   */
>
> +#ifdef CONFIG_XIP_KERNEL
> +#include "vmlinux-xip.lds.S"
> +#else
> +
>  #define LOAD_OFFSET PAGE_OFFSET
> +
>  #include <asm/vmlinux.lds.h>
>  #include <asm/page.h>
>  #include <asm/cache.h>
> @@ -132,3 +137,4 @@ SECTIONS
>
>  	DISCARDS
>  }
> +#endif /* CONFIG_XIP_KERNEL */
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 7f5036fbee8c..efe649d41f95 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -31,8 +31,8 @@ EXPORT_SYMBOL(empty_zero_page);
>
>  extern char _start[];
>  #define DTB_EARLY_BASE_VA      PGDIR_SIZE
> -void *dtb_early_va __initdata;
> -uintptr_t dtb_early_pa __initdata;
> +void *_dtb_early_va __initdata;
> +uintptr_t _dtb_early_pa __initdata;
>
>  struct pt_alloc_ops {
>  	pte_t *(*get_pte_virt)(phys_addr_t pa);
> @@ -88,6 +88,10 @@ static void print_vm_layout(void)
>  		  (unsigned long)VMALLOC_END);
>  	print_mlm("lowmem", (unsigned long)PAGE_OFFSET,
>  		  (unsigned long)high_memory);
> +#ifdef CONFIG_XIP_KERNEL
> +	print_mlm("xip", (unsigned long)XIP_VIRT_ADDR_START,
> +		  (unsigned long)XIP_VIRT_ADDR_START + SZ_16M);
> +#endif /* CONFIG_XIP_KERNEL */
>  }
>  #else
>  static void print_vm_layout(void) { }
> @@ -113,6 +117,10 @@ void __init setup_bootmem(void)
>  	phys_addr_t dram_end = memblock_end_of_DRAM();
>  	phys_addr_t max_mapped_addr = __pa(~(ulong)0);
>
> +#ifdef CONFIG_XIP_KERNEL
> +	vmlinux_start = __pa_symbol(&_sdata);
> +#endif
> +
>  	/* The maximal physical memory size is -PAGE_OFFSET. */
>  	memblock_enforce_memory_limit(-PAGE_OFFSET);
>
> @@ -149,11 +157,27 @@ void __init setup_bootmem(void)
>  	memblock_allow_resize();
>  }
>
> +#ifdef CONFIG_XIP_KERNEL
> +
> +extern char _xiprom[], _exiprom[];
> +extern char _sdata[], _edata[];
> +
> +#endif /* CONFIG_XIP_KERNEL */
> +
>  #ifdef CONFIG_MMU
> -static struct pt_alloc_ops pt_ops;
> +static struct pt_alloc_ops _pt_ops;
> +
> +#ifdef CONFIG_XIP_KERNEL
> +#define pt_ops (*(struct pt_alloc_ops *)XIP_FIXUP(&_pt_ops))
> +#else
> +#define pt_ops	_pt_ops
> +#endif
>
>  unsigned long va_pa_offset;
>  EXPORT_SYMBOL(va_pa_offset);
> +#ifdef CONFIG_XIP_KERNEL
> +#define va_pa_offset	(*((unsigned long *)XIP_FIXUP(&va_pa_offset)))
> +#endif
>  unsigned long pfn_base;
>  EXPORT_SYMBOL(pfn_base);
>
> @@ -163,6 +187,12 @@ pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
>
>  pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
>
> +#ifdef CONFIG_XIP_KERNEL
> +#define trampoline_pg_dir	((pgd_t *)XIP_FIXUP(trampoline_pg_dir))
> +#define fixmap_pte		((pte_t *)XIP_FIXUP(fixmap_pte))
> +#define early_pg_dir		((pgd_t *)XIP_FIXUP(early_pg_dir))
> +#endif /* CONFIG_XIP_KERNEL */
> +
>  void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
>  {
>  	unsigned long addr = __fix_to_virt(idx);
> @@ -238,6 +268,15 @@ pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
>  pmd_t early_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>  pmd_t early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>
> +#ifdef CONFIG_XIP_KERNEL
> +pmd_t xip_pmd[PTRS_PER_PMD] __page_aligned_bss;
> +
> +#define trampoline_pmd	((pmd_t *)XIP_FIXUP(trampoline_pmd))
> +#define fixmap_pmd	((pmd_t *)XIP_FIXUP(fixmap_pmd))
> +#define xip_pmd		((pmd_t *)XIP_FIXUP(xip_pmd))
> +#define early_pmd	((pmd_t *)XIP_FIXUP(early_pmd))
> +#endif /* CONFIG_XIP_KERNEL */
> +
>  static pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
>  {
>  	/* Before MMU is enabled */
> @@ -354,6 +393,19 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
>  	return PMD_SIZE;
>  }
>
> +#ifdef CONFIG_XIP_KERNEL
> +/* called from head.S with MMU off */
> +asmlinkage void __init __copy_data(void)
> +{
> +	void *from = (void *)(&_sdata);
> +	void *end = (void *)(&_end);
> +	void *to = (void *)CONFIG_PHYS_RAM_BASE;
> +	size_t sz = (size_t)(end - from);
> +
> +	memcpy(to, from, sz);
> +}
> +#endif
> +
>  /*
>   * setup_vm() is called from head.S with MMU-off.
>   *
> @@ -374,7 +426,8 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
>
>  asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>  {
> -	uintptr_t va, pa, end_va;
> +	uintptr_t va, end_va;
> +	uintptr_t __maybe_unused pa;
>  	uintptr_t load_pa = (uintptr_t)(&_start);
>  	uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
>  	uintptr_t map_size;
> @@ -382,6 +435,13 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>  	pmd_t fix_bmap_spmd, fix_bmap_epmd;
>  #endif
>
> +#ifdef CONFIG_XIP_KERNEL
> +	uintptr_t xiprom = (uintptr_t)CONFIG_XIP_PHYS_ADDR;
> +	uintptr_t xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
> +
> +	load_pa = (uintptr_t)CONFIG_PHYS_RAM_BASE;
> +	load_sz = (uintptr_t)(&_end) - (uintptr_t)(&_sdata);
> +#endif
>  	va_pa_offset = PAGE_OFFSET - load_pa;
>  	pfn_base = PFN_DOWN(load_pa);
>
> @@ -420,6 +480,21 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>  			   load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC);
>  #endif
>
> +#ifdef CONFIG_XIP_KERNEL
> +	create_pgd_mapping(trampoline_pg_dir, XIP_VIRT_ADDR_START,
> +			   (uintptr_t)xip_pmd, PGDIR_SIZE, PAGE_TABLE);
> +	for (va = XIP_VIRT_ADDR_START;
> +	     va < XIP_VIRT_ADDR_START + xiprom_sz;
> +	     va += PMD_SIZE) {
> +		create_pmd_mapping(xip_pmd, va,
> +				   xiprom + (va - XIP_VIRT_ADDR_START),
> +				   PMD_SIZE, PAGE_KERNEL_EXEC);
> +	}
> +
> +	create_pgd_mapping(early_pg_dir, XIP_VIRT_ADDR_START,
> +			   (uintptr_t)xip_pmd, PGDIR_SIZE, PAGE_TABLE);
> +#endif
> +
>  	/*
>  	 * Setup early PGD covering entire kernel which will allows
>  	 * us to reach paging_init(). We map all memory banks later
> @@ -444,7 +519,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>  			   pa + PMD_SIZE, PMD_SIZE, PAGE_KERNEL);
>  	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PMD_SIZE - 1));
>  #else /* CONFIG_BUILTIN_DTB */
> -	dtb_early_va = __va(dtb_pa);
> +	dtb_early_va = __va(XIP_FIXUP(dtb_pa));
>  #endif /* CONFIG_BUILTIN_DTB */
>  #else
>  #ifndef CONFIG_BUILTIN_DTB
> @@ -456,7 +531,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>  			   pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
>  	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PGDIR_SIZE - 1));
>  #else /* CONFIG_BUILTIN_DTB */
> -	dtb_early_va = __va(dtb_pa);
> +	dtb_early_va = __va(XIP_FIXUP(dtb_pa));
>  #endif /* CONFIG_BUILTIN_DTB */
>  #endif
>  	dtb_early_pa = dtb_pa;
> @@ -497,6 +572,9 @@ static void __init setup_vm_final(void)
>  	uintptr_t va, map_size;
>  	phys_addr_t pa, start, end;
>  	u64 i;
> +#ifdef CONFIG_XIP_KERNEL
> +	uintptr_t xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
> +#endif
>
>  	/**
>  	 * MMU is enabled at this point. But page table setup is not complete yet.
> @@ -528,6 +606,16 @@ static void __init setup_vm_final(void)
>  					   map_size, PAGE_KERNEL_EXEC);
>  		}
>  	}
> +#ifdef CONFIG_XIP_KERNEL
> +	map_size = best_map_size(CONFIG_XIP_PHYS_ADDR, xiprom_sz);
> +	for (va = XIP_VIRT_ADDR_START;
> +	     va < XIP_VIRT_ADDR_START + xiprom_sz;
> +	     va += map_size)
> +		create_pgd_mapping(swapper_pg_dir, va,
> +				   CONFIG_XIP_PHYS_ADDR + (va - XIP_VIRT_ADDR_START),
> +				   map_size, PAGE_KERNEL_EXEC);
> +
> +#endif
>
>  	/* Clear fixmap PTE and PMD mappings */
>  	clear_fixmap(FIX_PTE);