Messages in this thread | | | Date | Thu, 2 Oct 2008 02:06:15 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] ring_buffer: allocate buffer page pointer |
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On Thu, 2 Oct 2008 10:50:30 +0200 Ingo Molnar <mingo@elte.hu> wrote:
> > * Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > The current method of overlaying the page frame as the buffer page pointer > > can be very dangerous and limits our ability to do other things with > > a page from the buffer, like send it off to disk. > > > > This patch allocates the buffer_page instead of overlaying the page's > > page frame. The use of the buffer_page has hardly changed due to this. > > > > Signed-off-by: Steven Rostedt <srostedt@redhat.com> > > --- > > kernel/trace/ring_buffer.c | 54 ++++++++++++++++++++++++++------------------- > > 1 file changed, 32 insertions(+), 22 deletions(-) > > applied to tip/tracing/ftrace, with the extended changlog below - i > think this commit warrants that extra mention. > > Ingo > > ---------------> > >From da78331b4ced2763322d732ac5ba275965853bde Mon Sep 17 00:00:00 2001 > From: Steven Rostedt <rostedt@goodmis.org> > Date: Wed, 1 Oct 2008 10:52:51 -0400 > Subject: [PATCH] ftrace: type cast filter+verifier > > The mmiotrace map had a bug that would typecast the entry from > the trace to the wrong type. That is a known danger of C typecasts, > there's absolutely zero checking done on them. > > Help that problem a bit by using a GCC extension to implement a > type filter that restricts the types that a trace record can be > cast into, and by adding a dynamic check (in debug mode) to verify > the type of the entry. > > This patch adds a macro to assign all entries of ftrace using the type > of the variable and checking the entry id. The typecasts are now done > in the macro for only those types that it knows about, which should > be all the types that are allowed to be read from the tracer. >
I'm somewhat at a loss here because I'm unable to find any version of kernel/trace/trace.c which looks anything like the one which is being patched, but...
> --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -1350,7 +1350,9 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu) > } > switch (entry->type) { > case TRACE_FN: { > - struct ftrace_entry *field = (struct ftrace_entry *)entry;
Why was this code using a cast in the first place? It should be using entry->some_field_i_dont_have_here? That was the whole point in using the anonymous union in struct trace_entry?
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