xen: introduce helper functions to do safe read and write accesses (90fff3ea) · Commits · 戴 / test

arch/x86/include/asm/xen/page.h

+15 −1

Original line number	Diff line number	Diff line
		@@ -59,6 +59,20 @@ extern int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
		struct page **pages, unsigned int count);
		extern unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn);

		/*
		* Helper functions to write or read unsigned long values to/from
		* memory, when the access may fault.
		*/
		static inline int xen_safe_write_ulong(unsigned long *addr, unsigned long val)
		{
		return __put_user(val, (unsigned long __user *)addr);
		}

		static inline int xen_safe_read_ulong(unsigned long addr, unsigned long val)
		{
		return __get_user(val, (unsigned long __user )addr);
		}

		/*
		* When to use pfn_to_mfn(), __pfn_to_mfn() or get_phys_to_machine():
		* - pfn_to_mfn() returns either INVALID_P2M_ENTRY or the mfn. No indicator
		@@ -125,7 +139,7 @@ static inline unsigned long mfn_to_pfn_no_overrides(unsigned long mfn)
		* In such cases it doesn't matter what we return (we return garbage),
		* but we must handle the fault without crashing!
		*/
		ret = __get_user(pfn, &machine_to_phys_mapping[mfn]);
		ret = xen_safe_read_ulong(&machine_to_phys_mapping[mfn], &pfn);
		if (ret < 0)
		return ~0;

+1 −1

Original line number	Diff line number	Diff line
		@@ -625,7 +625,7 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
		return true;
		}

		if (likely(!__put_user(mfn, xen_p2m_addr + pfn)))
		if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
		return true;

		ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);