Messages in this thread Patch in this message | | | Date | Mon, 10 Sep 2018 17:39:38 +0800 | From | Feng Tang <> | Subject | Re: [PATCH] x86, mm: Reserver some memory for bootmem allocator for NO_BOOTMEM |
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On Fri, Sep 07, 2018 at 12:52:17PM +0200, Thomas Gleixner wrote: > On Fri, 7 Sep 2018, Feng Tang wrote: > > On Fri, Aug 31, 2018 at 09:36:59PM +0800, Feng Tang wrote: > > > Any sugestion? I can only have patch like this: > > > > Could you review this patch, as at this time window there is no usable memory > > block or other memory allocators that I know, so I follow the exisitng static > > fixmap page table code and add one more. > > You really want to add a proper sanity check for this. The static stuff has > to cover the fixmap. Just making it work for this particular case is sloppy > at best as the next larger change of the fixmap will just bring the problem > back. Yes, agree.
Since the issue happens very early before any serial console, I can only think of a build time check.
Thanks, Feng
--- arch/x86/kernel/head_64.S | 6 +++++- arch/x86/mm/pgtable.c | 13 +++++++++++++ 2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 15ebc2fc166e..3a1d33b43c29 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -448,11 +448,15 @@ NEXT_PAGE(level2_fixmap_pgt) .fill 506,8,0 .quad level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */ - .fill 5,8,0 + .quad level1_fixmap_pgt1 - __START_KERNEL_map + _PAGE_TABLE_NOENC + .fill 4,8,0 NEXT_PAGE(level1_fixmap_pgt) .fill 512,8,0 +NEXT_PAGE(level1_fixmap_pgt1) + .fill 512,8,0 + #undef PMDS .data diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index e848a4811785..fc172551048a 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -637,6 +637,19 @@ void __native_set_fixmap(enum fixed_addresses idx, pte_t pte) { unsigned long address = __fix_to_virt(idx); +#ifdef CONFIG_X86_64 + /* + * In arch/x86/kernel/head_64.S, the static page table + * has been setup for 4M space [-12M, -8M] + * 0xFFFFFFFFFF400000 ~ 0xFFFFFFFFFF7FFFFF + * Add a sanity check whether fixed_address crosses + * the boundary. + */ + #define FIXMAP_STATIC_PGTABLE_START 0xFFFFFFFFFF400000 + BUILD_BUG_ON(__fix_to_virt(__end_of_permanent_fixed_addresses) + < FIXMAP_STATIC_PGTABLE_START); +#endif + if (idx >= __end_of_fixed_addresses) { BUG(); return; -- 2.14.1 > > Thanks, > > tglx
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