lkml.org 
[lkml]   [2012]   [Apr]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/6] uprobes: introduce is_swbp_at_addr_fast()
From
Date
On Fri, 2012-04-06 at 00:21 +0200, Oleg Nesterov wrote:
> +int __weak is_swbp_at_addr_fast(unsigned long vaddr)
> +{
> + uprobe_opcode_t opcode;
> + int fault;
> +
> + pagefault_disable();
> + fault = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
> + sizeof(opcode));
> + pagefault_enable();
> +
> + if (unlikely(fault)) {
> + /*
> + * XXX: read_opcode() lacks FOLL_FORCE, it can fail if
> + * we race with another thread which does mprotect(NONE)
> + * after we hit bp.
> + */
> + if (read_opcode(current->mm, vaddr, &opcode))
> + return -EFAULT;
> + }
> +
> + return is_swbp_insn(&opcode);
> +}

Why bother with the pagefault_disable() and unlikely fault case and not
simply do copy_from_user() and have it deal with the fault if its needed
anyway?


\
 
 \ /
  Last update: 2012-04-16 12:11    [from the cache]
©2003-2011 Jasper Spaans