Messages in this thread | | | Date | Wed, 17 Feb 2016 10:29:45 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86/mm: Add x86 valid_phys_addr_range() for /dev/mem |
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* Toshi Kani <toshi.kani@hpe.com> wrote:
> x86 does not define ARCH_HAS_VALID_PHYS_ADDR_RANGE, which > leads /dev/mem to use the default valid_phys_addr_range() > and valid_mmap_phys_addr_range() in drivers/char/mem.c. > > The default valid_phys_addr_range() allows any range lower > than __pa(high_memory), which is the end of system RAM, and > disallows any range higher than it. > > Persistent memory may be located at lower and/or higher > address of __pa(high_memory) depending on their memory slots. > When using crash(8) via /dev/mem for analyzing data in > persistent memory, it can only access to the one lower than > __pa(high_memory). > > Add x86 valid_phys_addr_range() and valid_mmap_phys_addr_range() > to provide better checking: > - Physical address range is valid when it is fully backed by > IORESOURCE_MEM, regardless of __pa(high_memory). > - Other ranges, including holes, are invalid. > > This also allows crash(8) to access persistent memory ranges > via /dev/mem (with a minor change to remove high_memory check > from crash itself). > > Note, /dev/mem makes additional check with devmem_is_allowed() > for read/write when CONFIG_STRICT_DEVMEM is set, and does always > for mmap. CONFIG_IO_STRICT_DEVMEM provides further restriction. > > Signed-off-by: Toshi Kani <toshi.kani@hpe.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: Borislav Petkov <bp@suse.de> > Cc: Dan Williams <dan.j.williams@intel.com> > --- > This patch applies on top of the patch-set below, and is based > on the tip tree. > https://lkml.org/lkml/2016/1/26/886 > --- > arch/x86/include/asm/io.h | 3 +++ > arch/x86/mm/init.c | 24 ++++++++++++++++++++++++ > 2 files changed, 27 insertions(+) > > diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h > index de25aad..189901a 100644 > --- a/arch/x86/include/asm/io.h > +++ b/arch/x86/include/asm/io.h > @@ -36,6 +36,7 @@ > > #define ARCH_HAS_IOREMAP_WC > #define ARCH_HAS_IOREMAP_WT > +#define ARCH_HAS_VALID_PHYS_ADDR_RANGE > > #include <linux/string.h> > #include <linux/compiler.h> > @@ -326,6 +327,8 @@ extern void __iomem *ioremap_wc(resource_size_t offset, unsigned long size); > extern void __iomem *ioremap_wt(resource_size_t offset, unsigned long size); > > extern bool is_early_ioremap_ptep(pte_t *ptep); > +extern int valid_phys_addr_range(phys_addr_t addr, size_t size); > +extern int valid_mmap_phys_addr_range(unsigned long pfn, size_t size); > > #ifdef CONFIG_XEN > #include <xen/xen.h> > diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c > index 493f541..35cf96f 100644 > --- a/arch/x86/mm/init.c > +++ b/arch/x86/mm/init.c > @@ -624,6 +624,30 @@ void __init init_mem_mapping(void) > early_memtest(0, max_pfn_mapped << PAGE_SHIFT); > } > > +/** > + * valid_phys_addr_range - check phys addr for /dev/mem read and write > + * > + * Return true if a target physical address is marked as IORESOURCE_MEM. > + */ > +int valid_phys_addr_range(phys_addr_t addr, size_t size) > +{ > + return (region_intersects(addr, size, IORESOURCE_MEM, > + IORES_DESC_NONE) == REGION_INTERSECTS); > +} > + > +/** > + * valid_mmap_phys_addr_range - check phys addr for /dev/mem mmap > + * > + * Return true if a target physical address is marked as IORESOURCE_MEM. > + */ > +int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) > +{ > + resource_size_t addr = pfn << PAGE_SHIFT; > + > + return (region_intersects(addr, size, IORESOURCE_MEM, > + IORES_DESC_NONE) == REGION_INTERSECTS); > +} > + > /* > * devmem_is_allowed() checks to see if /dev/mem access to a certain address > * is valid. The argument is a physical page number.
So it's hard to judge the quality of these new APIs without seeing their actual usecases. So please Cc: me to whatever work this is used in, and I'll have a look in that context.
Thanks,
Ingo
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