Re: [PATCH] riscv: Fix 32b kernel caused by 64b kernel mapping moving outside linear mapping

[Palmer Dabbelt <palmer@dabbelt.com>]

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
>>>   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
>>>

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