Messages in this thread | | | Date | Thu, 26 Feb 2009 07:46:55 -0500 (EST) | From | Steven Rostedt <> | Subject | Re: [PATCH v2 0/5] [RFC] copy_strtok_from_user |
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On Thu, 26 Feb 2009, Ingo Molnar wrote:
> * Ingo Molnar <mingo@elte.hu> wrote: > > > > > * Peter Zijlstra <peterz@infradead.org> wrote: > > > > > On Thu, 2009-02-26 at 00:32 -0500, Steven Rostedt wrote: > > > > This is the second series of the uaccess code. > > > > > > > > Changes in v2: > > > > > > > > - moved probe_kernel_* functions to lib/uaccess.c > > > > > > > > - renamed copy_word_from_user to copy_strtok_from_user. > > > > > > > > - changed copy_strtok_from_user to pass in a delimiter string. > > > > ftrace defines SPACE to be ' \t\r\n'. > > > > > > > > Ingo, > > > > I added your copy right to lib/uaccess.c since git blame shows you > > > > as the author of the probe_kernel_* code. Also, is it OK that I > > > > added the "GPL v2" line in that file as well? > > > > > > > > Andrew, > > > > Since you are, in essence, the memory maintainer, could you give > > > > your Acked-by: to the copy_strtok_from_user code. > > > > > > > > The probe_kernel code is still EXPORT_SYMBOL_GPL, and I added > > > > that too to copy_strtok_from_user. Are there any objections to that? > > > > > > I have to ask,.. > > > > > > cant this be done with a regular copy_from_user() followed > > > by a regular strtok()? Do we really have to combine all > > > that? > > > > yes. Note that strsep() is the preferred API. (in fact it's > > the only such string API that is in the kernel) > > btw., for larger strings we cannot really copy into the kernel i > suspect. We'd have to kmalloc() and that adds overhead, etc. > > Nevertheless, copy_strsep_from_user() would be the symmetric API > here.
not really. strsep stops at the first delimiter. strtok skips multiple delimiters. I could implement the copy_strtok_from_user with a copy_from_user (all of read), and then use strtok_r (reentrant version) to find the next token. This would require implementing strtok_r for the kernel.
Having the copy_strtok_from_user will handle the copying and the caller would not need to worry about having a big enough buffer to hold delimiters and tokens. The copy_strtok_from_user would copy first to an internal buffer, then scan for tokens to copy into the callers buffer. Then repeat until read or copy limits have been hit.
-- Steve
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