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Subject: Re: [PATCH] riscv: Fix 32b kernel caused by 64b kernel mapping moving
 outside linear mapping
To:     Palmer Dabbelt <palmer@dabbelt.com>
Cc:     anup@brainfault.org, 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-5579c61f-d95b-4f9b-9f12-4df6bb24df0c@palmerdabbelt-glaptop>
From:   Alex Ghiti <alex@ghiti.fr>
Message-ID: <97819559-0af0-0422-5b6c-30872f759daa@ghiti.fr>
Date:   Fri, 23 Apr 2021 16:49:10 -0400
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Le 4/23/21 à 12:57 PM, Palmer Dabbelt a écrit :
> On Fri, 23 Apr 2021 01:34:02 PDT (-0700), alex@ghiti.fr wrote:
>> 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.
> 
> Agreed.  I'd recently sent out a patch set that got NACK'd because we're 
> supposed to be relying on the compiler to optimize away references that 
> can be staticly determined to not be exercised, which is probably the 
> way forward to getting rid of a lot of of preprocessor stuff.  That all 
> seems very fragile and is a bigger problem than this, though, so it's 
> probably best to do it as its own thing.
> 
>>> 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.
> 
> Thanks.  I just hadn't gotten to this one yet, but as you pointed out 
> it's probably best to just squash it.  It's in the version on for-next 
> now, it caused few conflicts but I think I got everything sorted out.
> 
> Now that everything is in I'm going to stop rewriting this stuff, as it 
> touches pretty much the whole tree.  I don't have much of a patch back 
> log as of right now, and as the new stuff will be on top of it that will 
> make everyone's lives easier.
> 
>>
>> 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

This one is incorrect as kernel_virt_addr is used also in 32b kernel, 
which causes 32b failure when CONFIG_DEBUG_VIRTUAL is set, the following 
diff fixes it:

diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index e280ba60cb34..6a7761c86ec2 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -106,9 +106,9 @@ extern unsigned long pfn_base;
  #define ARCH_PFN_OFFSET                (PAGE_OFFSET >> PAGE_SHIFT)
  #endif /* CONFIG_MMU */

-#ifdef CONFIG_64BIT
  extern unsigned long kernel_virt_addr;

+#ifdef CONFIG_64BIT
  #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)     ({ 
                  \

>>>>   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
>>>>

I agree with you, too much #ifdef, it is hardly readable: I take a look 
at how I can make it simpler.

Sorry for all those fixes,

Alex

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