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Subject: Re: [PATCH] riscv: Fix 32b kernel caused by 64b kernel mapping moving
 outside linear mapping
To:     Anup Patel <anup@brainfault.org>
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Arnd Bergmann <arnd@arndb.de>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>, linux-doc@vger.kernel.org,
        linux-riscv <linux-riscv@lists.infradead.org>,
        "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>,
        kasan-dev@googlegroups.com,
        linux-arch <linux-arch@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>
References: <20210417172159.32085-1-alex@ghiti.fr>
 <CAAhSdy23jRTp3VoBpnH8B79eSSmuw8qMEYrXyh-02ccWT3O5QQ@mail.gmail.com>
From:   Alex Ghiti <alex@ghiti.fr>
Message-ID: <66e9a8e0-5764-2eea-4070-bad3fb7ee48e@ghiti.fr>
Date:   Fri, 23 Apr 2021 04:34:02 -0400
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Le 4/20/21 à 12:18 AM, Anup Patel a écrit :
> On Sat, Apr 17, 2021 at 10:52 PM Alexandre Ghiti <alex@ghiti.fr> wrote:
>>
>> Fix multiple leftovers when moving the kernel mapping outside the linear
>> mapping for 64b kernel that left the 32b kernel unusable.
>>
>> Fixes: 4b67f48da707 ("riscv: Move kernel mapping outside of linear mapping")
>> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
> 
> Quite a few #ifdef but I don't see any better way at the moment. Maybe we can
> clean this later. Otherwise looks good to me.
> 
> Reviewed-by: Anup Patel <anup@brainfault.org>

Thanks Anup!

@Palmer: This is not on for-next yet and then rv32 is broken. This does 
not apply immediately on top of for-next though, so if you need a new 
version, I can do that. But this squashes nicely with the patch it fixes 
if you prefer.

Let me know, I can do that very quickly.

Alex

> 
> Regards,
> Anup
> 
>> ---
>>   arch/riscv/include/asm/page.h    |  9 +++++++++
>>   arch/riscv/include/asm/pgtable.h | 16 ++++++++++++----
>>   arch/riscv/mm/init.c             | 25 ++++++++++++++++++++++++-
>>   3 files changed, 45 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
>> index 22cfb2be60dc..f64b61296c0c 100644
>> --- a/arch/riscv/include/asm/page.h
>> +++ b/arch/riscv/include/asm/page.h
>> @@ -90,15 +90,20 @@ typedef struct page *pgtable_t;
>>
>>   #ifdef CONFIG_MMU
>>   extern unsigned long va_pa_offset;
>> +#ifdef CONFIG_64BIT
>>   extern unsigned long va_kernel_pa_offset;
>> +#endif
>>   extern unsigned long pfn_base;
>>   #define ARCH_PFN_OFFSET                (pfn_base)
>>   #else
>>   #define va_pa_offset           0
>> +#ifdef CONFIG_64BIT
>>   #define va_kernel_pa_offset    0
>> +#endif
>>   #define ARCH_PFN_OFFSET                (PAGE_OFFSET >> PAGE_SHIFT)
>>   #endif /* CONFIG_MMU */
>>
>> +#ifdef CONFIG_64BIT
>>   extern unsigned long kernel_virt_addr;
>>
>>   #define linear_mapping_pa_to_va(x)     ((void *)((unsigned long)(x) + va_pa_offset))
>> @@ -112,6 +117,10 @@ extern unsigned long kernel_virt_addr;
>>          (_x < kernel_virt_addr) ?                                               \
>>                  linear_mapping_va_to_pa(_x) : kernel_mapping_va_to_pa(_x);      \
>>          })
>> +#else
>> +#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)
>> +#endif
>>
>>   #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 80e63a93e903..5afda75cc2c3 100644
>> --- a/arch/riscv/include/asm/pgtable.h
>> +++ b/arch/riscv/include/asm/pgtable.h
>> @@ -16,19 +16,27 @@
>>   #else
>>
>>   #define ADDRESS_SPACE_END      (UL(-1))
>> -/*
>> - * Leave 2GB for kernel and BPF at the end of the address space
>> - */
>> +
>> +#ifdef CONFIG_64BIT
>> +/* Leave 2GB for kernel and BPF at the end of the address space */
>>   #define KERNEL_LINK_ADDR       (ADDRESS_SPACE_END - SZ_2G + 1)
>> +#else
>> +#define KERNEL_LINK_ADDR       PAGE_OFFSET
>> +#endif
>>
>>   #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)
>> +#ifdef CONFIG_64BIT
>> +/* KASLR should leave at least 128MB for BPF after the kernel */
>>   #define BPF_JIT_REGION_START   PFN_ALIGN((unsigned long)&_end)
>>   #define BPF_JIT_REGION_END     (BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE)
>> +#else
>> +#define BPF_JIT_REGION_START   (PAGE_OFFSET - BPF_JIT_REGION_SIZE)
>> +#define BPF_JIT_REGION_END     (VMALLOC_END)
>> +#endif
>>
>>   /* Modules always live before the kernel */
>>   #ifdef CONFIG_64BIT
>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>> index 093f3a96ecfc..dc9b988e0778 100644
>> --- a/arch/riscv/mm/init.c
>> +++ b/arch/riscv/mm/init.c
>> @@ -91,8 +91,10 @@ static void print_vm_layout(void)
>>                    (unsigned long)VMALLOC_END);
>>          print_mlm("lowmem", (unsigned long)PAGE_OFFSET,
>>                    (unsigned long)high_memory);
>> +#ifdef CONFIG_64BIT
>>          print_mlm("kernel", (unsigned long)KERNEL_LINK_ADDR,
>>                    (unsigned long)ADDRESS_SPACE_END);
>> +#endif
>>   }
>>   #else
>>   static void print_vm_layout(void) { }
>> @@ -165,9 +167,11 @@ 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);
>> +#ifdef CONFIG_64BIT
>>   /* Offset between kernel mapping virtual address and kernel load address */
>>   unsigned long va_kernel_pa_offset;
>>   EXPORT_SYMBOL(va_kernel_pa_offset);
>> +#endif
>>   unsigned long pfn_base;
>>   EXPORT_SYMBOL(pfn_base);
>>
>> @@ -410,7 +414,9 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>          load_sz = (uintptr_t)(&_end) - load_pa;
>>
>>          va_pa_offset = PAGE_OFFSET - load_pa;
>> +#ifdef CONFIG_64BIT
>>          va_kernel_pa_offset = kernel_virt_addr - load_pa;
>> +#endif
>>
>>          pfn_base = PFN_DOWN(load_pa);
>>
>> @@ -469,12 +475,16 @@ 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 */
>> +#ifdef CONFIG_64BIT
>>          /*
>>           * __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);
>> +#else
>> +       dtb_early_va = __va(dtb_pa);
>> +#endif /* CONFIG_64BIT */
>>   #endif /* CONFIG_BUILTIN_DTB */
>>   #else
>>   #ifndef CONFIG_BUILTIN_DTB
>> @@ -486,7 +496,11 @@ 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 */
>> +#ifdef CONFIG_64BIT
>>          dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
>> +#else
>> +       dtb_early_va = __va(dtb_pa);
>> +#endif /* CONFIG_64BIT */
>>   #endif /* CONFIG_BUILTIN_DTB */
>>   #endif
>>          dtb_early_pa = dtb_pa;
>> @@ -571,12 +585,21 @@ 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);
>> +                                          map_size,
>> +#ifdef CONFIG_64BIT
>> +                                          PAGE_KERNEL
>> +#else
>> +                                          PAGE_KERNEL_EXEC
>> +#endif
>> +                                       );
>> +
>>                  }
>>          }
>>
>> +#ifdef CONFIG_64BIT
>>          /* Map the kernel */
>>          create_kernel_page_table(swapper_pg_dir, PMD_SIZE);
>> +#endif
>>
>>          /* Clear fixmap PTE and PMD mappings */
>>          clear_fixmap(FIX_PTE);
>> --
>> 2.20.1
>>