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Re: [Qemu-devel] [PATCH] scripts/dump-guest-memory.py: fix int128_get64
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] scripts/dump-guest-memory.py: fix int128_get64 on recent gcc |
Date: |
Fri, 10 Mar 2017 11:58:00 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 |
On 10/03/2017 11:54, Marc-André Lureau wrote:
> Hi
>
> On Fri, Mar 10, 2017 at 2:00 PM Paolo Bonzini <address@hidden
> <mailto:address@hidden>> wrote:
>
>
>
> On 10/03/2017 09:53, Marc-André Lureau wrote:
> > The Int128 is no longer a struct, reaching a python exception:
> > Python Exception <class 'gdb.error'> Attempt to extract a
> component of a value that is not a (null).:
> >
> > Replace struct access with a cast to uint64 instead.
> >
> > Fixes:
> > https://bugzilla.redhat.com/show_bug.cgi?id=1427466
> >
> > Signed-off-by: Marc-André Lureau <address@hidden
> <mailto:address@hidden>>
> > ---
> > scripts/dump-guest-memory.py | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/scripts/dump-guest-memory.py
> b/scripts/dump-guest-memory.py
> > index 9956fc036c..bbe1c14ba2 100644
> > --- a/scripts/dump-guest-memory.py
> > +++ b/scripts/dump-guest-memory.py
> > @@ -314,8 +314,10 @@ def get_arch_phdr(endianness, elfclass):
> > def int128_get64(val):
> > """Returns low 64bit part of Int128 struct."""
> >
> > - assert val["hi"] == 0
> > - return val["lo"]
> > + u64t = gdb.lookup_type('uint64_t').array(2)
> > + u64 = val.cast(u64t)
> > + assert u64[1] == 0
> > + return u64[0]
> >
> >
> > def qlist_foreach(head, field_str):
> >
>
> I'm afraid this is not big-endian-friendly (Python lets you check that
> with "sys.byteorder == 'little'").
>
> Also when building on a 32-bit machine the old code should be used; I
> think you need to use try/except to choose between the two.
>
>
> Do you think that would be enough?
>
> diff --git a/scripts/dump-guest-memory.py b/scripts/dump-guest-memory.py
> index 9956fc036c..f7c6635f15 100644
> --- a/scripts/dump-guest-memory.py
> +++ b/scripts/dump-guest-memory.py
> @@ -314,8 +314,18 @@ def get_arch_phdr(endianness, elfclass):
> def int128_get64(val):
> """Returns low 64bit part of Int128 struct."""
>
> - assert val["hi"] == 0
> - return val["lo"]
> + try:
> + assert val["hi"] == 0
> + return val["lo"]
> + except gdb.error:
> + u64t = gdb.lookup_type('uint64_t').array(2)
> + u64 = val.cast(u64t)
> + if sys.byteorder == 'little':
> + assert u64[1] == 0
> + return u64[0]
> + else:
> + assert u64[0] == 0
> + return u64[1]
>
> (I don't have a 32-bit system handy to check it, and cross-compilation
> with m32 etc is tricky to get right, I am trying though)
Yes, this should work.
Paolo