Re: [PATCH v8] RISC-V: enable XIP

[Alex Ghiti <alex@ghiti.fr>]

Hi Palmer,

Le 4/23/21 à 12:22 AM, Palmer Dabbelt a écrit :
> On Mon, 12 Apr 2021 23:35:14 PDT (-0700), alex@ghiti.fr wrote:
>> From: Vitaly Wool <vitaly.wool@konsulko.com>
>>
>> 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: Alexandre Ghiti <alex@ghiti.fr> [ Rebase on top of "Move
>> kernel mapping outside the linear mapping" ]
>> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
>> ---
>>  arch/riscv/Kconfig                  |  55 +++++++++++-
>>  arch/riscv/Makefile                 |   8 +-
>>  arch/riscv/boot/Makefile            |  13 +++
>>  arch/riscv/include/asm/page.h       |  21 +++++
>>  arch/riscv/include/asm/pgtable.h    |  25 +++++-
>>  arch/riscv/kernel/head.S            |  46 +++++++++-
>>  arch/riscv/kernel/head.h            |   3 +
>>  arch/riscv/kernel/setup.c           |  10 ++-
>>  arch/riscv/kernel/vmlinux-xip.lds.S | 133 ++++++++++++++++++++++++++++
>>  arch/riscv/kernel/vmlinux.lds.S     |   6 ++
>>  arch/riscv/mm/init.c                | 115 ++++++++++++++++++++++--
>>  11 files changed, 418 insertions(+), 17 deletions(-)
>>  create mode 100644 arch/riscv/kernel/vmlinux-xip.lds.S
>>
>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index 8ea60a0a19ae..7c7efdd67a10 100644
>> --- a/arch/riscv/Kconfig
>> +++ b/arch/riscv/Kconfig
>> @@ -28,7 +28,7 @@ config RISCV
>>      select ARCH_HAS_PTE_SPECIAL
>>      select ARCH_HAS_SET_DIRECT_MAP
>>      select ARCH_HAS_SET_MEMORY
>> -    select ARCH_HAS_STRICT_KERNEL_RWX if MMU
>> +    select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
> 
> We now also have STRICT_MODULE_RWX, which causes a merge conflict.  I've 
> added both as !XIP_KERNEL, though TBH I'm not even sure thot modules 
> make any sense with XIP.
> 
>>      select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>>      select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
>>      select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
>> @@ -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 +465,60 @@ 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 && SPARSEMEM
>> +    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.
>> +
>> +      SPARSEMEM is required because the kernel text and rodata that are
>> +      flash resident are not backed by memmap, then any attempt to get
>> +      a struct page on those regions will trigger a fault.
>> +
>> +      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/page.h 
>> b/arch/riscv/include/asm/page.h
>> index 22cfb2be60dc..635c6b486806 100644
>> --- a/arch/riscv/include/asm/page.h
>> +++ b/arch/riscv/include/asm/page.h
>> @@ -91,6 +91,9 @@ typedef struct page *pgtable_t;
>>  #ifdef CONFIG_MMU
>>  extern unsigned long va_pa_offset;
>>  extern unsigned long va_kernel_pa_offset;
>> +#ifdef CONFIG_XIP_KERNEL
>> +extern unsigned long va_kernel_xip_pa_offset;
>> +#endif
>>  extern unsigned long pfn_base;
>>  #define ARCH_PFN_OFFSET        (pfn_base)
>>  #else
>> @@ -102,11 +105,29 @@ extern unsigned long pfn_base;
>>  extern unsigned long kernel_virt_addr;
>>
>>  #define linear_mapping_pa_to_va(x)    ((void *)((unsigned long)(x) + 
>> va_pa_offset))
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define kernel_mapping_pa_to_va(y)    ({                        \
>> +    unsigned long _y = y;                                \
>> +    (_y >= CONFIG_PHYS_RAM_BASE) ?                            \
>> +        (void *)((unsigned long)(_y) + va_kernel_pa_offset + 
>> XIP_OFFSET) :    \
>> +        (void *)((unsigned long)(_y) + 
>> va_kernel_xip_pa_offset);        \
>> +    })
>> +#else
>>  #define kernel_mapping_pa_to_va(x)    ((void *)((unsigned long)(x) + 
>> va_kernel_pa_offset))
>> +#endif
>>  #define __pa_to_va_nodebug(x)        linear_mapping_pa_to_va(x)
>>
>>  #define linear_mapping_va_to_pa(x)    ((unsigned long)(x) - 
>> va_pa_offset)
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define kernel_mapping_va_to_pa(y) ({                        \
>> +    unsigned long _y = y;                            \
>> +    (_y < kernel_virt_addr + XIP_OFFSET) ?                    \
>> +        ((unsigned long)(_y) - va_kernel_xip_pa_offset) :        \
>> +        ((unsigned long)(_y) - va_kernel_pa_offset - XIP_OFFSET);    \
>> +    })
>> +#else
>>  #define kernel_mapping_va_to_pa(x)    ((unsigned long)(x) - 
>> va_kernel_pa_offset)
>> +#endif
>>  #define __va_to_pa_nodebug(x)    ({                        \
>>      unsigned long _x = x;                            \
>>      (_x < kernel_virt_addr) ?                        \
>> diff --git a/arch/riscv/include/asm/pgtable.h 
>> b/arch/riscv/include/asm/pgtable.h
>> index 80e63a93e903..c2dc4f83eed8 100644
>> --- a/arch/riscv/include/asm/pgtable.h
>> +++ b/arch/riscv/include/asm/pgtable.h
>> @@ -64,6 +64,19 @@
>>  #define FIXADDR_SIZE     PGDIR_SIZE
>>  #endif
>>  #define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)
>> +
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define XIP_OFFSET        SZ_8M
>> +#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 */
>> +
>>  #endif
>>
>>  #ifndef __ASSEMBLY__
>> @@ -499,8 +512,16 @@ static inline int ptep_clear_flush_young(struct 
>> vm_area_struct *vma,
>>  #define kern_addr_valid(addr)   (1) /* FIXME */
>>
>>  extern char _start[];
>> -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/head.S b/arch/riscv/kernel/head.S
>> index 6cb05f22e52a..89cc58ab52b4 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)
>>      /*
>> @@ -70,6 +82,7 @@ pe_head_start:
>>  relocate:
>>      /* Relocate return address */
>>      la a1, kernel_virt_addr
>> +    XIP_FIXUP_OFFSET a1
>>      REG_L a1, 0(a1)
>>      la a2, _start
>>      sub a1, a1, a2
>> @@ -92,6 +105,7 @@ 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
>> @@ -145,7 +159,9 @@ 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)
>> @@ -157,6 +173,7 @@ 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
>> @@ -237,12 +254,33 @@ 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
>> @@ -252,15 +290,18 @@ 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
>> @@ -269,6 +310,7 @@ clear_bss_done:
>>      call setup_vm
>>  #ifdef CONFIG_MMU
>>      la a0, early_pg_dir
>> +    XIP_FIXUP_OFFSET a0
>>      call relocate
>>  #endif /* CONFIG_MMU */
>>
>> @@ -293,7 +335,9 @@ 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 30e4af0fd50c..2ddf654c72bb 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");
>> @@ -266,7 +270,7 @@ void __init setup_arch(char **cmdline_p)
>>      if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
>>          protect_kernel_text_data();
>>
>> -#if defined(CONFIG_64BIT) && defined(CONFIG_MMU)
>> +#if defined(CONFIG_64BIT) && defined(CONFIG_MMU) && 
>> !defined(CONFIG_XIP_KERNEL)
>>      protect_kernel_linear_mapping_text_rodata();
>>  #endif
> 
> My tree doesn't look quite like this.

Yes, this is because you have the patch "riscv: Protect kernel linear 
mapping only if CONFIG_STRICT_KERNEL_RWX is set".

> Not sure if I just got the wrong 
> version of something, but I didn't have the CONFIG_MMU check.  It turns 
> out that, as I was merging this in, I saw that failing allnoconfig 
> (which is !MMU).  I went ahead and squashed in
> 
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index ab394d173cd4..3e7930869ee7 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -266,7 +266,7 @@ void __init setup_arch(char **cmdline_p)
> 
>      if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) {
>          protect_kernel_text_data();
> -#ifdef CONFIG_64BIT
> +#if defined(CONFIG_64BIT) && defined(CONFIG_MMU)

You did the right thing here, I thought the MMU check was not necessary 
since STRICT_KERNEL_RWX depends on MMU but the check is done at 
runtime...My bad.

>          protect_kernel_linear_mapping_text_rodata();
> #endif
>      }
> 
> to your memory map rearrangement patch, but I'm a bit worried that I 
> managed to
> miss something in the process.

I gave it a try and it works as expected on for-next.

Thanks,

Alex

> 
>>
>> diff --git a/arch/riscv/kernel/vmlinux-xip.lds.S 
>> b/arch/riscv/kernel/vmlinux-xip.lds.S
>> new file mode 100644
>> index 000000000000..4b29b9917f99
>> --- /dev/null
>> +++ b/arch/riscv/kernel/vmlinux-xip.lds.S
>> @@ -0,0 +1,133 @@
>> +/* 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
>> + */
>> +
>> +#include <asm/pgtable.h>
>> +#define LOAD_OFFSET KERNEL_LINK_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 */
>> +    . = LOAD_OFFSET;
>> +    _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 */
>> +    . = LOAD_OFFSET + XIP_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 0726c05e0336..0a59b65cf789 100644
>> --- a/arch/riscv/kernel/vmlinux.lds.S
>> +++ b/arch/riscv/kernel/vmlinux.lds.S
>> @@ -4,8 +4,13 @@
>>   * Copyright (C) 2017 SiFive
>>   */
>>
>> +#ifdef CONFIG_XIP_KERNEL
>> +#include "vmlinux-xip.lds.S"
>> +#else
>> +
>>  #include <asm/pgtable.h>
>>  #define LOAD_OFFSET KERNEL_LINK_ADDR
>> +
>>  #include <asm/vmlinux.lds.h>
>>  #include <asm/page.h>
>>  #include <asm/cache.h>
>> @@ -133,3 +138,4 @@ SECTIONS
>>
>>      DISCARDS
>>  }
>> +#endif /* CONFIG_XIP_KERNEL */
>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>> index 093f3a96ecfc..d03e5e43d2d0 100644
>> --- a/arch/riscv/mm/init.c
>> +++ b/arch/riscv/mm/init.c
>> @@ -27,6 +27,9 @@
>>
>>  unsigned long kernel_virt_addr = KERNEL_LINK_ADDR;
>>  EXPORT_SYMBOL(kernel_virt_addr);
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define kernel_virt_addr       (*((unsigned long 
>> *)XIP_FIXUP(&kernel_virt_addr)))
>> +#endif
>>
>>  unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
>>                              __page_aligned_bss;
>> @@ -34,8 +37,8 @@ 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);
>> @@ -118,6 +121,10 @@ 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);
>>
>> @@ -159,15 +166,39 @@ 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
>>
>>  /* Offset between linear mapping virtual address and kernel load 
>> address */
>>  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
>>  /* Offset between kernel mapping virtual address and kernel load 
>> address */
>>  unsigned long va_kernel_pa_offset;
>>  EXPORT_SYMBOL(va_kernel_pa_offset);
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define va_kernel_pa_offset    (*((unsigned long 
>> *)XIP_FIXUP(&va_kernel_pa_offset)))
>> +#endif
>> +unsigned long va_kernel_xip_pa_offset;
>> +EXPORT_SYMBOL(va_kernel_xip_pa_offset);
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define va_kernel_xip_pa_offset        (*((unsigned long 
>> *)XIP_FIXUP(&va_kernel_xip_pa_offset)))
>> +#endif
>>  unsigned long pfn_base;
>>  EXPORT_SYMBOL(pfn_base);
>>
>> @@ -177,6 +208,12 @@ 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);
>> @@ -252,6 +289,12 @@ 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
>> +#define trampoline_pmd ((pmd_t *)XIP_FIXUP(trampoline_pmd))
>> +#define fixmap_pmd     ((pmd_t *)XIP_FIXUP(fixmap_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 */
>> @@ -368,6 +411,19 @@ 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 + 1);
>> +
>> +    memcpy(to, from, sz);
>> +}
>> +#endif
>> +
>>  /*
>>   * setup_vm() is called from head.S with MMU-off.
>>   *
>> @@ -387,7 +443,35 @@ static uintptr_t __init best_map_size(phys_addr_t 
>> base, phys_addr_t size)
>>  #endif
>>
>>  uintptr_t load_pa, load_sz;
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define load_pa        (*((uintptr_t *)XIP_FIXUP(&load_pa)))
>> +#define load_sz        (*((uintptr_t *)XIP_FIXUP(&load_sz)))
>> +#endif
>> +
>> +#ifdef CONFIG_XIP_KERNEL
>> +uintptr_t xiprom, xiprom_sz;
>> +#define xiprom_sz      (*((uintptr_t *)XIP_FIXUP(&xiprom_sz)))
>> +#define xiprom         (*((uintptr_t *)XIP_FIXUP(&xiprom)))
>>
>> +static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t 
>> map_size)
>> +{
>> +    uintptr_t va, end_va;
>> +
>> +    /* Map the flash resident part */
>> +    end_va = kernel_virt_addr + xiprom_sz;
>> +    for (va = kernel_virt_addr; va < end_va; va += map_size)
>> +        create_pgd_mapping(pgdir, va,
>> +                   xiprom + (va - kernel_virt_addr),
>> +                   map_size, PAGE_KERNEL_EXEC);
>> +
>> +    /* Map the data in RAM */
>> +    end_va = kernel_virt_addr + XIP_OFFSET + load_sz;
>> +    for (va = kernel_virt_addr + XIP_OFFSET; va < end_va; va += 
>> map_size)
>> +        create_pgd_mapping(pgdir, va,
>> +                   load_pa + (va - (kernel_virt_addr + XIP_OFFSET)),
>> +                   map_size, PAGE_KERNEL);
>> +}
>> +#else
>>  static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t 
>> map_size)
>>  {
>>      uintptr_t va, end_va;
>> @@ -398,16 +482,28 @@ static void __init 
>> create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
>>                     load_pa + (va - kernel_virt_addr),
>>                     map_size, PAGE_KERNEL_EXEC);
>>  }
>> +#endif
>>
>>  asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>  {
>> -    uintptr_t pa;
>> +    uintptr_t __maybe_unused pa;
>>      uintptr_t map_size;
>>  #ifndef __PAGETABLE_PMD_FOLDED
>>      pmd_t fix_bmap_spmd, fix_bmap_epmd;
>>  #endif
>> +
>> +#ifdef CONFIG_XIP_KERNEL
>> +    xiprom = (uintptr_t)CONFIG_XIP_PHYS_ADDR;
>> +    xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
>> +
>> +    load_pa = (uintptr_t)CONFIG_PHYS_RAM_BASE;
>> +    load_sz = (uintptr_t)(&_end) - (uintptr_t)(&_sdata);
>> +
>> +    va_kernel_xip_pa_offset = kernel_virt_addr - xiprom;
>> +#else
>>      load_pa = (uintptr_t)(&_start);
>>      load_sz = (uintptr_t)(&_end) - load_pa;
>> +#endif
>>
>>      va_pa_offset = PAGE_OFFSET - load_pa;
>>      va_kernel_pa_offset = kernel_virt_addr - load_pa;
>> @@ -441,8 +537,13 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>      /* Setup trampoline PGD and PMD */
>>      create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>>                 (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
>> +#ifdef CONFIG_XIP_KERNEL
>> +    create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>> +               xiprom, PMD_SIZE, PAGE_KERNEL_EXEC);
>> +#else
>>      create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>>                 load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
>> +#endif
>>  #else
>>      /* Setup trampoline PGD */
>>      create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>> @@ -474,7 +575,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>       * whereas dtb_early_va will be used before setup_vm_final installs
>>       * the linear mapping.
>>       */
>> -    dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
>> +    dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
>>  #endif /* CONFIG_BUILTIN_DTB */
>>  #else
>>  #ifndef CONFIG_BUILTIN_DTB
>> @@ -486,7 +587,7 @@ 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 = kernel_mapping_pa_to_va(dtb_pa);
>> +    dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
>>  #endif /* CONFIG_BUILTIN_DTB */
>>  #endif
>>      dtb_early_pa = dtb_pa;
>> @@ -522,7 +623,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>  #endif
>>  }
>>
>> -#ifdef CONFIG_64BIT
>> +#if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
>>  void protect_kernel_linear_mapping_text_rodata(void)
>>  {
>>      unsigned long text_start = (unsigned long)lm_alias(_start);
> 
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