[PATCH] TraceWriterQEMU.cc: Change strncpy to memcpy

[Joel Sherrill]

On Wed, Sep 1, 2021 at 3:26 PM Ryan Long <ryan.long at oarcorp.com> wrote:
>
>
>
> -----Original Message-----
> From: Gedare Bloom <gedare at rtems.org>
> Sent: Wednesday, September 1, 2021 3:21 PM
> To: Ryan Long <ryan.long at oarcorp.com>
> Cc: devel at rtems.org
> Subject: Re: [PATCH] TraceWriterQEMU.cc: Change strncpy to memcpy
>
> On Thu, Aug 19, 2021 at 7:42 AM Ryan Long <ryan.long at oarcorp.com> wrote:
> >
> > CID 1506207: Buffer not null terminated
> >
> > Closes #4491
> > ---
> >  tester/covoar/TraceWriterQEMU.cc | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/tester/covoar/TraceWriterQEMU.cc
> > b/tester/covoar/TraceWriterQEMU.cc
> > index c417745..be9b6e1 100644
> > --- a/tester/covoar/TraceWriterQEMU.cc
> > +++ b/tester/covoar/TraceWriterQEMU.cc
> > @@ -106,7 +106,10 @@ namespace Trace {
> >      //
> >      //  Write the Header to the file
> >      //
> > -    strncpy( header.magic, QEMU_TRACE_MAGIC, sizeof(header.magic) );
> > +    // The header.magic field is actually 12 bytes, but QEMU_TRACE_MAGIC is
> > +    // 13 bytes including the NULL.
> > +    const char qemu_trace_magic[13] = QEMU_TRACE_MAGIC;
> > +    memcpy( header.magic, qemu_trace_magic, sizeof(header.magic) );
>
> Just to clarify, the header.magic should not be NULL terminated?
> [Ryan Long] Correct. When I tried to increase the size of header.magic, it wouldn't run correctly.
>
> If so, then this is fine, but I don't think the temporary local variable is needed though.
> memcpy( header.magic, QEMU_TRACE_MAGIC, sizeof(header.magic) ); should work fine.

The qemu trace format for couverture has that format without the NUL
termination.
I'm not sure in their rationale for doing it that way but it is 12 magic bytes.

>
> >      header.version = QEMU_TRACE_VERSION;
> >      header.kind    = QEMU_TRACE_KIND_RAW;  // XXX ??
> >      header.sizeof_target_pc = 32;
> > --
> > 1.8.3.1
> >
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