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Subject: Re: [PATCH v5 1/3] riscv: Move kernel mapping outside of linear
 mapping
From:   Alex Ghiti <alex@ghiti.fr>
To:     Palmer Dabbelt <palmer@dabbelt.com>
Cc:     corbet@lwn.net, Paul Walmsley <paul.walmsley@sifive.com>,
        aou@eecs.berkeley.edu, Arnd Bergmann <arnd@arndb.de>,
        aryabinin@virtuozzo.com, glider@google.com, dvyukov@google.com,
        linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org,
        linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
        linux-arch@vger.kernel.org, linux-mm@kvack.org
References: <mhng-90fff6bd-5a70-4927-98c1-a515a7448e71@palmerdabbelt-glaptop>
 <76353fc0-f734-db47-0d0c-f0f379763aa0@ghiti.fr>
Message-ID: <a58c4616-572f-4a0b-2ce9-fd00735843be@ghiti.fr>
Date:   Thu, 15 Apr 2021 14:00:21 -0400
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Le 4/15/21 à 12:54 AM, Alex Ghiti a écrit :
> Le 4/15/21 à 12:20 AM, Palmer Dabbelt a écrit :
>> On Sun, 11 Apr 2021 09:41:44 PDT (-0700), alex@ghiti.fr wrote:
>>> This is a preparatory patch for relocatable kernel and sv48 support.
>>>
>>> The kernel used to be linked at PAGE_OFFSET address therefore we 
>>> could use
>>> the linear mapping for the kernel mapping. But the relocated kernel base
>>> address will be different from PAGE_OFFSET and since in the linear 
>>> mapping,
>>> two different virtual addresses cannot point to the same physical 
>>> address,
>>> the kernel mapping needs to lie outside the linear mapping so that we 
>>> don't
>>> have to copy it at the same physical offset.
>>>
>>> The kernel mapping is moved to the last 2GB of the address space, BPF
>>> is now always after the kernel and modules use the 2GB memory range 
>>> right
>>> before the kernel, so BPF and modules regions do not overlap. KASLR
>>> implementation will simply have to move the kernel in the last 2GB range
>>> and just take care of leaving enough space for BPF.
>>>
>>> In addition, by moving the kernel to the end of the address space, both
>>> sv39 and sv48 kernels will be exactly the same without needing to be
>>> relocated at runtime.
>>>
>>> Suggested-by: Arnd Bergmann <arnd@arndb.de>
>>> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
>>> ---
>>>  arch/riscv/boot/loader.lds.S        |  3 +-
>>>  arch/riscv/include/asm/page.h       | 17 +++++-
>>>  arch/riscv/include/asm/pgtable.h    | 37 ++++++++----
>>>  arch/riscv/include/asm/set_memory.h |  1 +
>>>  arch/riscv/kernel/head.S            |  3 +-
>>>  arch/riscv/kernel/module.c          |  6 +-
>>>  arch/riscv/kernel/setup.c           |  5 ++
>>>  arch/riscv/kernel/vmlinux.lds.S     |  3 +-
>>>  arch/riscv/mm/fault.c               | 13 +++++
>>>  arch/riscv/mm/init.c                | 87 ++++++++++++++++++++++-------
>>>  arch/riscv/mm/kasan_init.c          |  9 +++
>>>  arch/riscv/mm/physaddr.c            |  2 +-
>>>  12 files changed, 146 insertions(+), 40 deletions(-)
>>>
>>> diff --git a/arch/riscv/boot/loader.lds.S b/arch/riscv/boot/loader.lds.S
>>> index 47a5003c2e28..62d94696a19c 100644
>>> --- a/arch/riscv/boot/loader.lds.S
>>> +++ b/arch/riscv/boot/loader.lds.S
>>> @@ -1,13 +1,14 @@
>>>  /* SPDX-License-Identifier: GPL-2.0 */
>>>
>>>  #include <asm/page.h>
>>> +#include <asm/pgtable.h>
>>>
>>>  OUTPUT_ARCH(riscv)
>>>  ENTRY(_start)
>>>
>>>  SECTIONS
>>>  {
>>> -    . = PAGE_OFFSET;
>>> +    . = KERNEL_LINK_ADDR;
>>>
>>>      .payload : {
>>>          *(.payload)
>>> diff --git a/arch/riscv/include/asm/page.h 
>>> b/arch/riscv/include/asm/page.h
>>> index adc9d26f3d75..22cfb2be60dc 100644
>>> --- a/arch/riscv/include/asm/page.h
>>> +++ b/arch/riscv/include/asm/page.h
>>> @@ -90,15 +90,28 @@ typedef struct page *pgtable_t;
>>>
>>>  #ifdef CONFIG_MMU
>>>  extern unsigned long va_pa_offset;
>>> +extern unsigned long va_kernel_pa_offset;
>>>  extern unsigned long pfn_base;
>>>  #define ARCH_PFN_OFFSET        (pfn_base)
>>>  #else
>>>  #define va_pa_offset        0
>>> +#define va_kernel_pa_offset    0
>>>  #define ARCH_PFN_OFFSET        (PAGE_OFFSET >> PAGE_SHIFT)
>>>  #endif /* CONFIG_MMU */
>>>
>>> -#define __pa_to_va_nodebug(x)    ((void *)((unsigned long) (x) + 
>>> va_pa_offset))
>>> -#define __va_to_pa_nodebug(x)    ((unsigned long)(x) - va_pa_offset)
>>> +extern unsigned long kernel_virt_addr;
>>> +
>>> +#define linear_mapping_pa_to_va(x)    ((void *)((unsigned long)(x) + 
>>> va_pa_offset))
>>> +#define kernel_mapping_pa_to_va(x)    ((void *)((unsigned long)(x) + 
>>> va_kernel_pa_offset))
>>> +#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)
>>> +#define kernel_mapping_va_to_pa(x)    ((unsigned long)(x) - 
>>> va_kernel_pa_offset)
>>> +#define __va_to_pa_nodebug(x)    ({                        \
>>> +    unsigned long _x = x;                            \
>>> +    (_x < kernel_virt_addr) ?                        \
>>> +        linear_mapping_va_to_pa(_x) : kernel_mapping_va_to_pa(_x);    \
>>> +    })
>>>
>>>  #ifdef CONFIG_DEBUG_VIRTUAL
>>>  extern phys_addr_t __virt_to_phys(unsigned long x);
>>> diff --git a/arch/riscv/include/asm/pgtable.h 
>>> b/arch/riscv/include/asm/pgtable.h
>>> index ebf817c1bdf4..80e63a93e903 100644
>>> --- a/arch/riscv/include/asm/pgtable.h
>>> +++ b/arch/riscv/include/asm/pgtable.h
>>> @@ -11,23 +11,30 @@
>>>
>>>  #include <asm/pgtable-bits.h>
>>>
>>> -#ifndef __ASSEMBLY__
>>> -
>>> -/* Page Upper Directory not used in RISC-V */
>>> -#include <asm-generic/pgtable-nopud.h>
>>> -#include <asm/page.h>
>>> -#include <asm/tlbflush.h>
>>> -#include <linux/mm_types.h>
>>> +#ifndef CONFIG_MMU
>>> +#define KERNEL_LINK_ADDR    PAGE_OFFSET
>>> +#else
>>>
>>> -#ifdef CONFIG_MMU
>>> +#define ADDRESS_SPACE_END    (UL(-1))
>>> +/*
>>> + * Leave 2GB for kernel and BPF at the end of the address space
>>> + */
>>> +#define KERNEL_LINK_ADDR    (ADDRESS_SPACE_END - SZ_2G + 1)
>>>
>>>  #define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
>>>  #define VMALLOC_END      (PAGE_OFFSET - 1)
>>>  #define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
>>>
>>> +/* KASLR should leave at least 128MB for BPF after the kernel */
>>>  #define BPF_JIT_REGION_SIZE    (SZ_128M)
>>> -#define BPF_JIT_REGION_START    (PAGE_OFFSET - BPF_JIT_REGION_SIZE)
>>> -#define BPF_JIT_REGION_END    (VMALLOC_END)
>>> +#define BPF_JIT_REGION_START    PFN_ALIGN((unsigned long)&_end)
>>> +#define BPF_JIT_REGION_END    (BPF_JIT_REGION_START + 
>>> BPF_JIT_REGION_SIZE)
>>> +
>>> +/* Modules always live before the kernel */
>>> +#ifdef CONFIG_64BIT
>>> +#define MODULES_VADDR    (PFN_ALIGN((unsigned long)&_end) - SZ_2G)
>>> +#define MODULES_END    (PFN_ALIGN((unsigned long)&_start))
>>> +#endif
>>>
>>>  /*
>>>   * Roughly size the vmemmap space to be large enough to fit enough
>>> @@ -57,9 +64,16 @@
>>>  #define FIXADDR_SIZE     PGDIR_SIZE
>>>  #endif
>>>  #define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)
>>> -
>>>  #endif
>>>
>>> +#ifndef __ASSEMBLY__
>>> +
>>> +/* Page Upper Directory not used in RISC-V */
>>> +#include <asm-generic/pgtable-nopud.h>
>>> +#include <asm/page.h>
>>> +#include <asm/tlbflush.h>
>>> +#include <linux/mm_types.h>
>>> +
>>>  #ifdef CONFIG_64BIT
>>>  #include <asm/pgtable-64.h>
>>>  #else
>>> @@ -484,6 +498,7 @@ 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;
>>>  void setup_bootmem(void);
>>> diff --git a/arch/riscv/include/asm/set_memory.h 
>>> b/arch/riscv/include/asm/set_memory.h
>>> index 6887b3d9f371..a9c56776fa0e 100644
>>> --- a/arch/riscv/include/asm/set_memory.h
>>> +++ b/arch/riscv/include/asm/set_memory.h
>>> @@ -17,6 +17,7 @@ int set_memory_x(unsigned long addr, int numpages);
>>>  int set_memory_nx(unsigned long addr, int numpages);
>>>  int set_memory_rw_nx(unsigned long addr, int numpages);
>>>  void protect_kernel_text_data(void);
>>> +void protect_kernel_linear_mapping_text_rodata(void);
>>>  #else
>>>  static inline int set_memory_ro(unsigned long addr, int numpages) { 
>>> return 0; }
>>>  static inline int set_memory_rw(unsigned long addr, int numpages) { 
>>> return 0; }
>>> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
>>> index f5a9bad86e58..6cb05f22e52a 100644
>>> --- a/arch/riscv/kernel/head.S
>>> +++ b/arch/riscv/kernel/head.S
>>> @@ -69,7 +69,8 @@ pe_head_start:
>>>  #ifdef CONFIG_MMU
>>>  relocate:
>>>      /* Relocate return address */
>>> -    li a1, PAGE_OFFSET
>>> +    la a1, kernel_virt_addr
>>> +    REG_L a1, 0(a1)
>>>      la a2, _start
>>>      sub a1, a1, a2
>>>      add ra, ra, a1
>>> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
>>> index 104fba889cf7..ce153771e5e9 100644
>>> --- a/arch/riscv/kernel/module.c
>>> +++ b/arch/riscv/kernel/module.c
>>> @@ -408,12 +408,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const 
>>> char *strtab,
>>>  }
>>>
>>>  #if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
>>> -#define VMALLOC_MODULE_START \
>>> -     max(PFN_ALIGN((unsigned long)&_end - SZ_2G), VMALLOC_START)
>>>  void *module_alloc(unsigned long size)
>>>  {
>>> -    return __vmalloc_node_range(size, 1, VMALLOC_MODULE_START,
>>> -                    VMALLOC_END, GFP_KERNEL,
>>> +    return __vmalloc_node_range(size, 1, MODULES_VADDR,
>>> +                    MODULES_END, GFP_KERNEL,
>>>                      PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
>>>                      __builtin_return_address(0));
>>>  }
>>> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
>>> index e85bacff1b50..30e4af0fd50c 100644
>>> --- a/arch/riscv/kernel/setup.c
>>> +++ b/arch/riscv/kernel/setup.c
>>> @@ -265,6 +265,11 @@ 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)
>>> +    protect_kernel_linear_mapping_text_rodata();
>>> +#endif
>>> +
>>>  #ifdef CONFIG_SWIOTLB
>>>      swiotlb_init(1);
>>>  #endif
>>> diff --git a/arch/riscv/kernel/vmlinux.lds.S 
>>> b/arch/riscv/kernel/vmlinux.lds.S
>>> index de03cb22d0e9..0726c05e0336 100644
>>> --- a/arch/riscv/kernel/vmlinux.lds.S
>>> +++ b/arch/riscv/kernel/vmlinux.lds.S
>>> @@ -4,7 +4,8 @@
>>>   * Copyright (C) 2017 SiFive
>>>   */
>>>
>>> -#define LOAD_OFFSET PAGE_OFFSET
>>> +#include <asm/pgtable.h>
>>> +#define LOAD_OFFSET KERNEL_LINK_ADDR
>>>  #include <asm/vmlinux.lds.h>
>>>  #include <asm/page.h>
>>>  #include <asm/cache.h>
>>> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
>>> index 8f17519208c7..1b14d523a95c 100644
>>> --- a/arch/riscv/mm/fault.c
>>> +++ b/arch/riscv/mm/fault.c
>>> @@ -231,6 +231,19 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>>>          return;
>>>      }
>>>
>>> +#ifdef CONFIG_64BIT
>>> +    /*
>>> +     * Modules in 64bit kernels lie in their own virtual region 
>>> which is not
>>> +     * in the vmalloc region, but dealing with page faults in this 
>>> region
>>> +     * or the vmalloc region amounts to doing the same thing: 
>>> checking that
>>> +     * the mapping exists in init_mm.pgd and updating user page 
>>> table, so
>>> +     * just use vmalloc_fault.
>>> +     */
>>> +    if (unlikely(addr >= MODULES_VADDR && addr < MODULES_END)) {
>>> +        vmalloc_fault(regs, code, addr);
>>> +        return;
>>> +    }
>>> +#endif
>>>      /* Enable interrupts if they were enabled in the parent context. */
>>>      if (likely(regs->status & SR_PIE))
>>>          local_irq_enable();
>>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>>> index 7f5036fbee8c..093f3a96ecfc 100644
>>> --- a/arch/riscv/mm/init.c
>>> +++ b/arch/riscv/mm/init.c
>>> @@ -25,6 +25,9 @@
>>>
>>>  #include "../kernel/head.h"
>>>
>>> +unsigned long kernel_virt_addr = KERNEL_LINK_ADDR;
>>> +EXPORT_SYMBOL(kernel_virt_addr);
>>> +
>>>  unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
>>>                              __page_aligned_bss;
>>>  EXPORT_SYMBOL(empty_zero_page);
>>> @@ -88,6 +91,8 @@ static void print_vm_layout(void)
>>>            (unsigned long)VMALLOC_END);
>>>      print_mlm("lowmem", (unsigned long)PAGE_OFFSET,
>>>            (unsigned long)high_memory);
>>> +    print_mlm("kernel", (unsigned long)KERNEL_LINK_ADDR,
>>> +          (unsigned long)ADDRESS_SPACE_END);
>>>  }
>>>  #else
>>>  static void print_vm_layout(void) { }
>>> @@ -116,8 +121,13 @@ void __init setup_bootmem(void)
>>>      /* The maximal physical memory size is -PAGE_OFFSET. */
>>>      memblock_enforce_memory_limit(-PAGE_OFFSET);
>>>
>>> -    /* Reserve from the start of the kernel to the end of the kernel */
>>> -    memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
>>> +    /*
>>> +     * Reserve from the start of the kernel to the end of the kernel
>>> +     * and make sure we align the reservation on PMD_SIZE since we will
>>> +     * map the kernel in the linear mapping as read-only: we do not 
>>> want
>>> +     * any allocation to happen between _end and the next pmd 
>>> aligned page.
>>> +     */
>>> +    memblock_reserve(vmlinux_start, (vmlinux_end - vmlinux_start + 
>>> PMD_SIZE - 1) & PMD_MASK);
>>>
>>>      /*
>>>       * memblock allocator is not aware of the fact that last 4K 
>>> bytes of
>>> @@ -152,8 +162,12 @@ void __init setup_bootmem(void)
>>>  #ifdef CONFIG_MMU
>>>  static struct pt_alloc_ops pt_ops;
>>>
>>> +/* Offset between linear mapping virtual address and kernel load 
>>> address */
>>>  unsigned long va_pa_offset;
>>>  EXPORT_SYMBOL(va_pa_offset);
>>> +/* Offset between kernel mapping virtual address and kernel load 
>>> address */
>>> +unsigned long va_kernel_pa_offset;
>>> +EXPORT_SYMBOL(va_kernel_pa_offset);
>>>  unsigned long pfn_base;
>>>  EXPORT_SYMBOL(pfn_base);
>>>
>>> @@ -257,7 +271,7 @@ static pmd_t *get_pmd_virt_late(phys_addr_t pa)
>>>
>>>  static phys_addr_t __init alloc_pmd_early(uintptr_t va)
>>>  {
>>> -    BUG_ON((va - PAGE_OFFSET) >> PGDIR_SHIFT);
>>> +    BUG_ON((va - kernel_virt_addr) >> PGDIR_SHIFT);
>>>
>>>      return (uintptr_t)early_pmd;
>>>  }
>>> @@ -372,17 +386,32 @@ static uintptr_t __init 
>>> best_map_size(phys_addr_t base, phys_addr_t size)
>>>  #error "setup_vm() is called from head.S before relocate so it 
>>> should not use absolute addressing."
>>>  #endif
>>>
>>> +uintptr_t load_pa, load_sz;
>>> +
>>> +static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t 
>>> map_size)
>>> +{
>>> +    uintptr_t va, end_va;
>>> +
>>> +    end_va = kernel_virt_addr + load_sz;
>>> +    for (va = kernel_virt_addr; va < end_va; va += map_size)
>>> +        create_pgd_mapping(pgdir, va,
>>> +                   load_pa + (va - kernel_virt_addr),
>>> +                   map_size, PAGE_KERNEL_EXEC);
>>> +}
>>> +
>>>  asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>>  {
>>> -    uintptr_t va, pa, end_va;
>>> -    uintptr_t load_pa = (uintptr_t)(&_start);
>>> -    uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
>>> +    uintptr_t pa;
>>>      uintptr_t map_size;
>>>  #ifndef __PAGETABLE_PMD_FOLDED
>>>      pmd_t fix_bmap_spmd, fix_bmap_epmd;
>>>  #endif
>>> +    load_pa = (uintptr_t)(&_start);
>>> +    load_sz = (uintptr_t)(&_end) - load_pa;
>>>
>>>      va_pa_offset = PAGE_OFFSET - load_pa;
>>> +    va_kernel_pa_offset = kernel_virt_addr - load_pa;
>>> +
>>>      pfn_base = PFN_DOWN(load_pa);
>>>
>>>      /*
>>> @@ -410,26 +439,22 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>>      create_pmd_mapping(fixmap_pmd, FIXADDR_START,
>>>                 (uintptr_t)fixmap_pte, PMD_SIZE, PAGE_TABLE);
>>>      /* Setup trampoline PGD and PMD */
>>> -    create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
>>> +    create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>>>                 (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
>>> -    create_pmd_mapping(trampoline_pmd, PAGE_OFFSET,
>>> +    create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>>>                 load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
>>>  #else
>>>      /* Setup trampoline PGD */
>>> -    create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
>>> +    create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>>>                 load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC);
>>>  #endif
>>>
>>>      /*
>>> -     * Setup early PGD covering entire kernel which will allows
>>> +     * Setup early PGD covering entire kernel which will allow
>>>       * us to reach paging_init(). We map all memory banks later
>>>       * in setup_vm_final() below.
>>>       */
>>> -    end_va = PAGE_OFFSET + load_sz;
>>> -    for (va = PAGE_OFFSET; va < end_va; va += map_size)
>>> -        create_pgd_mapping(early_pg_dir, va,
>>> -                   load_pa + (va - PAGE_OFFSET),
>>> -                   map_size, PAGE_KERNEL_EXEC);
>>> +    create_kernel_page_table(early_pg_dir, map_size);
>>>
>>>  #ifndef __PAGETABLE_PMD_FOLDED
>>>      /* Setup early PMD for DTB */
>>> @@ -444,7 +469,12 @@ 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);
>>> +    /*
>>> +     * __va can't be used since it would return a linear mapping 
>>> address
>>> +     * 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);
>>>  #endif /* CONFIG_BUILTIN_DTB */
>>>  #else
>>>  #ifndef CONFIG_BUILTIN_DTB
>>> @@ -456,7 +486,7 @@ 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 = kernel_mapping_pa_to_va(dtb_pa);
>>>  #endif /* CONFIG_BUILTIN_DTB */
>>>  #endif
>>>      dtb_early_pa = dtb_pa;
>>> @@ -492,6 +522,22 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>>  #endif
>>>  }
>>>
>>> +#ifdef CONFIG_64BIT
>>> +void protect_kernel_linear_mapping_text_rodata(void)
>>> +{
>>> +    unsigned long text_start = (unsigned long)lm_alias(_start);
>>> +    unsigned long init_text_start = (unsigned 
>>> long)lm_alias(__init_text_begin);
>>> +    unsigned long rodata_start = (unsigned 
>>> long)lm_alias(__start_rodata);
>>> +    unsigned long data_start = (unsigned long)lm_alias(_data);
>>> +
>>> +    set_memory_ro(text_start, (init_text_start - text_start) >> 
>>> PAGE_SHIFT);
>>> +    set_memory_nx(text_start, (init_text_start - text_start) >> 
>>> PAGE_SHIFT);
>>> +
>>> +    set_memory_ro(rodata_start, (data_start - rodata_start) >> 
>>> PAGE_SHIFT);
>>> +    set_memory_nx(rodata_start, (data_start - rodata_start) >> 
>>> PAGE_SHIFT);
>>> +}
>>> +#endif
>>> +
>>>  static void __init setup_vm_final(void)
>>>  {
>>>      uintptr_t va, map_size;
>>> @@ -513,7 +559,7 @@ static void __init setup_vm_final(void)
>>>                 __pa_symbol(fixmap_pgd_next),
>>>                 PGDIR_SIZE, PAGE_TABLE);
>>>
>>> -    /* Map all memory banks */
>>> +    /* Map all memory banks in the linear mapping */
>>>      for_each_mem_range(i, &start, &end) {
>>>          if (start >= end)
>>>              break;
>>> @@ -525,10 +571,13 @@ static void __init setup_vm_final(void)
>>>          for (pa = start; pa < end; pa += map_size) {
>>>              va = (uintptr_t)__va(pa);
>>>              create_pgd_mapping(swapper_pg_dir, va, pa,
>>> -                       map_size, PAGE_KERNEL_EXEC);
>>> +                       map_size, PAGE_KERNEL);
>>>          }
>>>      }
>>>
>>> +    /* Map the kernel */
>>> +    create_kernel_page_table(swapper_pg_dir, PMD_SIZE);
>>> +
>>>      /* Clear fixmap PTE and PMD mappings */
>>>      clear_fixmap(FIX_PTE);
>>>      clear_fixmap(FIX_PMD);
>>> diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
>>> index 2c39f0386673..28f4d52cf17e 100644
>>> --- a/arch/riscv/mm/kasan_init.c
>>> +++ b/arch/riscv/mm/kasan_init.c
>>> @@ -171,6 +171,10 @@ void __init kasan_init(void)
>>>      phys_addr_t _start, _end;
>>>      u64 i;
>>>
>>> +    /*
>>> +     * Populate all kernel virtual address space with 
>>> kasan_early_shadow_page
>>> +     * except for the linear mapping and the modules/kernel/BPF 
>>> mapping.
>>> +     */
>>>      kasan_populate_early_shadow((void *)KASAN_SHADOW_START,
>>>                      (void *)kasan_mem_to_shadow((void *)
>>>                                  VMEMMAP_END));
>>> @@ -183,6 +187,7 @@ void __init kasan_init(void)
>>>              (void *)kasan_mem_to_shadow((void *)VMALLOC_START),
>>>              (void *)kasan_mem_to_shadow((void *)VMALLOC_END));
>>>
>>> +    /* Populate the linear mapping */
>>>      for_each_mem_range(i, &_start, &_end) {
>>>          void *start = (void *)__va(_start);
>>>          void *end = (void *)__va(_end);
>>> @@ -193,6 +198,10 @@ void __init kasan_init(void)
>>>          kasan_populate(kasan_mem_to_shadow(start), 
>>> kasan_mem_to_shadow(end));
>>>      };
>>>
>>> +    /* Populate kernel, BPF, modules mapping */
>>> +    kasan_populate(kasan_mem_to_shadow((const void *)MODULES_VADDR),
>>> +               kasan_mem_to_shadow((const void *)BPF_JIT_REGION_END));
>>> +
>>>      for (i = 0; i < PTRS_PER_PTE; i++)
>>>          set_pte(&kasan_early_shadow_pte[i],
>>>              mk_pte(virt_to_page(kasan_early_shadow_page),
>>> diff --git a/arch/riscv/mm/physaddr.c b/arch/riscv/mm/physaddr.c
>>> index e8e4dcd39fed..35703d5ef5fd 100644
>>> --- a/arch/riscv/mm/physaddr.c
>>> +++ b/arch/riscv/mm/physaddr.c
>>> @@ -23,7 +23,7 @@ EXPORT_SYMBOL(__virt_to_phys);
>>>
>>>  phys_addr_t __phys_addr_symbol(unsigned long x)
>>>  {
>>> -    unsigned long kernel_start = (unsigned long)PAGE_OFFSET;
>>> +    unsigned long kernel_start = (unsigned long)kernel_virt_addr;
>>>      unsigned long kernel_end = (unsigned long)_end;
>>>
>>>      /*
>>
>> This is breaking boot for me with CONFIG_STRICT_KERNEL_RWX=n.  I'm not 
>> even really convinced that's a useful config to support, but it's 
>> currently optional and I'd prefer to avoid breaking it if possible.
>>
>> I can't quite figure out what's going on here and I'm pretty much 
>> tired out for tonight.  LMK if you don't have time to look at it and 
>> I'll try to give it another shot.
> 
> I'm taking a look at that.

Just to make sure you don't miss it, I fixed this issue in 
https://patchwork.kernel.org/project/linux-riscv/patch/20210415110426.2238-1-alex@ghiti.fr/

Thanks,

Alex

> 
> Thanks,
> 
> Alex
> 
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