On Mon, 2009-09-14 at 10:09 -0700, Christopher Li wrote:
> On Mon, Sep 14, 2009 at 8:16 AM, Steven Rostedt <srostedt@xxxxxxxxxx> wrote:
> > static void func(int size_me) {
> > char array[size_me];
> >
> > memcpy(array, "hello", size);
> > };
> >
> > and sparse failed on it as well. Note, you need to have something call
> > func, or sparse will ignore it.
>
> Gcc allows variable size. Sparse expects the size of an array is constant.
> For the kernel using variable array size is consider bad. Because the kernel
> has very limited stack size. (8K if I remember correctly). Using dynamic array
> is very easy to overflow the stack without realizing it.
>
> It deserves a warning. I agree the warning message can use a better description
> though.
Good point!
I've added Frederic to the Cc list, since he wrote the code.
Frederic, how big can one of those events get. The ring buffer (and
TRACE_EVENT) allow up to almost a page size, which is very hefty for the
stack. This code needs to either be rewritten or we need to set a limit
to the size of a profile entry.
We could add:
if (__entry_size > 256)
return;
Thoughts?
-- Steve
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