[Qemu-devel] [PATCH] scripts/dump-guest-memory.py: fix int128_get64 on recent gcc

[Qemu-devel] [PATCH] scripts/dump-guest-memory.py: fix int128_get64 on recent gcc

[Marc-André Lureau]

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 <marcandre.lureau@redhat.com>
---
 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):
-- 
2.12.0.rc2.3.gc93709801

Re: [Qemu-devel] [PATCH] scripts/dump-guest-memory.py: fix int128_get64 on recent gcc

[Paolo Bonzini]

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 <marcandre.lureau@redhat.com>
> ---
>  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.

Paolo

Re: [Qemu-devel] [PATCH] scripts/dump-guest-memory.py: fix int128_get64 on recent gcc

[Marc-André Lureau]

Hi

On Fri, Mar 10, 2017 at 2:00 PM Paolo Bonzini <pbonzini@redhat.com> 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 <marcandre.lureau@redhat.com>
> > ---
> >  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)


> Paolo
>
> --
Marc-André Lureau

Re: [Qemu-devel] [PATCH] scripts/dump-guest-memory.py: fix int128_get64 on recent gcc

[Paolo Bonzini]

On 10/03/2017 11:54, Marc-André Lureau wrote:
> Hi
> 
> On Fri, Mar 10, 2017 at 2:00 PM Paolo Bonzini <pbonzini@redhat.com
> <mailto:pbonzini@redhat.com>> 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 <marcandre.lureau@redhat.com
>     <mailto:marcandre.lureau@redhat.com>>
>     > ---
>     >  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