linux-kernel - Re: [PATCH v10 20/22] x86: mm: Convert dump_pagetables to use walk_page

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Date:   Tue, 6 Aug 2019 16:58:23 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Steven Price <steven.price@....com>
Cc:     linux-mm@...ck.org, Andy Lutomirski <luto@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        James Morse <james.morse@....com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Rutland <Mark.Rutland@....com>,
        "Liang, Kan" <kan.liang@...ux.intel.com>
Subject: Re: [PATCH v10 20/22] x86: mm: Convert dump_pagetables to use
 walk_page_range

On Wed, 31 Jul 2019 16:46:01 +0100 Steven Price <steven.price@....com> wrote:

> Make use of the new functionality in walk_page_range to remove the
> arch page walking code and use the generic code to walk the page tables.
> 
> The effective permissions are passed down the chain using new fields
> in struct pg_state.
> 
> The KASAN optimisation is implemented by including test_p?d callbacks
> which can decide to skip an entire tree of entries
> 
> ...
>
> +static const struct ptdump_range ptdump_ranges[] = {
> +#ifdef CONFIG_X86_64
>  
> -#define pgd_large(a) (pgtable_l5_enabled() ? pgd_large(a) : p4d_large(__p4d(pgd_val(a))))
> -#define pgd_none(a)  (pgtable_l5_enabled() ? pgd_none(a) : p4d_none(__p4d(pgd_val(a))))
> +#define normalize_addr_shift (64 - (__VIRTUAL_MASK_SHIFT + 1))
> +#define normalize_addr(u) ((signed long)(u << normalize_addr_shift) \
> +				>> normalize_addr_shift)
>  
> -static inline bool is_hypervisor_range(int idx)
> -{
> -#ifdef CONFIG_X86_64
> -	/*
> -	 * A hole in the beginning of kernel address space reserved
> -	 * for a hypervisor.
> -	 */
> -	return	(idx >= pgd_index(GUARD_HOLE_BASE_ADDR)) &&
> -		(idx <  pgd_index(GUARD_HOLE_END_ADDR));
> +	{0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
> +	{normalize_addr(PTRS_PER_PGD * PGD_LEVEL_MULT / 2), ~0UL},

This blows up because PGD_LEVEL_MULT is sometimes not a constant.

x86_64 allmodconfig:

In file included from ./arch/x86/include/asm/pgtable_types.h:249:0,
                 from ./arch/x86/include/asm/paravirt_types.h:45,
                 from ./arch/x86/include/asm/ptrace.h:94,
                 from ./arch/x86/include/asm/math_emu.h:5,
                 from ./arch/x86/include/asm/processor.h:12,
                 from ./arch/x86/include/asm/cpufeature.h:5,
                 from ./arch/x86/include/asm/thread_info.h:53,
                 from ./include/linux/thread_info.h:38,
                 from ./arch/x86/include/asm/preempt.h:7,
                 from ./include/linux/preempt.h:78,
                 from ./include/linux/spinlock.h:51,
                 from ./include/linux/wait.h:9,
                 from ./include/linux/wait_bit.h:8,
                 from ./include/linux/fs.h:6,
                 from ./include/linux/debugfs.h:15,
                 from arch/x86/mm/dump_pagetables.c:11:
./arch/x86/include/asm/pgtable_64_types.h:56:22: error: initializer element is not constant
 #define PTRS_PER_PGD 512
                      ^
arch/x86/mm/dump_pagetables.c:363:6: note: in expansion of macro ‘PTRS_PER_PGD’
  {0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
      ^~~~~~~~~~~~
./arch/x86/include/asm/pgtable_64_types.h:56:22: note: (near initialization for ‘ptdump_ranges[0].end’)
 #define PTRS_PER_PGD 512
                      ^
arch/x86/mm/dump_pagetables.c:363:6: note: in expansion of macro ‘PTRS_PER_PGD’
  {0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
      ^~~~~~~~~~~~
arch/x86/mm/dump_pagetables.c:360:27: error: initializer element is not constant
 #define normalize_addr(u) ((signed long)(u << normalize_addr_shift) \
                           ^
arch/x86/mm/dump_pagetables.c:364:3: note: in expansion of macro ‘normalize_addr’
  {normalize_addr(PTRS_PER_PGD * PGD_LEVEL_MULT / 2), ~0UL},
   ^~~~~~~~~~~~~~
arch/x86/mm/dump_pagetables.c:360:27: note: (near initialization for ‘ptdump_ranges[1].start’)
 #define normalize_addr(u) ((signed long)(u << normalize_addr_shift) \
                           ^
arch/x86/mm/dump_pagetables.c:364:3: note: in expansion of macro ‘normalize_addr’
  {normalize_addr(PTRS_PER_PGD * PGD_LEVEL_MULT / 2), ~0UL},

I don't know what to do about this so I'll drop the series.