diff options
Diffstat (limited to 'arch/x86/include/asm/uaccess.h')
| -rw-r--r-- | arch/x86/include/asm/uaccess.h | 39 |
1 files changed, 35 insertions, 4 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 457e814712af..123135d60f72 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -75,6 +75,34 @@ static inline unsigned long __untagged_addr_remote(struct mm_struct *mm, #define untagged_addr(addr) (addr) #endif +#ifdef CONFIG_X86_64 +/* + * On x86-64, we may have tag bits in the user pointer. Rather than + * mask them off, just change the rules for __access_ok(). + * + * Make the rule be that 'ptr+size' must not overflow, and must not + * have the high bit set. Compilers generally understand about + * unsigned overflow and the CF bit and generate reasonable code for + * this. Although it looks like the combination confuses at least + * clang (and instead of just doing an "add" followed by a test of + * SF and CF, you'll see that unnecessary comparison). + * + * For the common case of small sizes that can be checked at compile + * time, don't even bother with the addition, and just check that the + * base pointer is ok. + */ +static inline bool __access_ok(const void __user *ptr, unsigned long size) +{ + if (__builtin_constant_p(size <= PAGE_SIZE) && size <= PAGE_SIZE) { + return (long)ptr >= 0; + } else { + unsigned long sum = size + (unsigned long)ptr; + return (long) sum >= 0 && sum >= (unsigned long)ptr; + } +} +#define __access_ok __access_ok +#endif + /** * access_ok - Checks if a user space pointer is valid * @addr: User space pointer to start of block to check @@ -91,11 +119,14 @@ static inline unsigned long __untagged_addr_remote(struct mm_struct *mm, * * Return: true (nonzero) if the memory block may be valid, false (zero) * if it is definitely invalid. + * + * This should not be x86-specific. The only odd things out here is + * the WARN_ON_IN_IRQ(), which doesn't exist in the generic version. */ -#define access_ok(addr, size) \ -({ \ - WARN_ON_IN_IRQ(); \ - likely(__access_ok(untagged_addr(addr), size)); \ +#define access_ok(addr, size) \ +({ \ + WARN_ON_IN_IRQ(); \ + likely(__access_ok(addr, size)); \ }) #include <asm-generic/access_ok.h> |