Messages in this thread Patch in this message | | | Date | Tue, 11 Jul 2006 16:42:08 -0700 | From | Andrew Morton <> | Subject | Re: [patch] i386: handle_BUG(): don't print garbage if debug info unavailable |
| |
Linus Torvalds <torvalds@osdl.org> wrote: > > That said, I think it's wrong to use "__get_user()", which can hang on the > MM semaphore if something is bogus. We should probably mark us as being > "in_atomic()" to make sure that the page fault handler, if it is entered, > will not try to get the semaphore or page anything in.
This?
--- a/include/linux/uaccess.h~add-probe_kernel_address +++ a/include/linux/uaccess.h @@ -19,4 +19,26 @@ static inline unsigned long __copy_from_ #endif /* ARCH_HAS_NOCACHE_UACCESS */ +/** + * probe_kernel_address(): safely attempt to read from a location + * @addr: address to read from - its type is type typeof(retval)* + * @retval: read into this variable + * + * Safely read from address @addr into variable @revtal. If a kernel fault + * happens, handle that and return -EFAULT. + * We ensure that the __get_user() is executed in atomic context so that + * do_page_fault() doesn't attempt to take mmap_sem. This makes + * probe_kernel_address() suitable for use within regions where the caller + * already holds mmap_sem, or other locks which nest inside mmap_sem. + */ +#define probe_kernel_address(addr, retval) \ + ({ \ + long ret; \ + \ + inc_preempt_count(); \ + ret = __get_user(retval, addr); \ + dec_preempt_count(); \ + ret; \ + }) + #endif /* __LINUX_UACCESS_H__ */ _ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |