RE: [PATCH] sysinfo: include availram field in sysinfo struct

David Laight
2022-01-07T22:18:38Z

> > These are the header changes for quick look:
> > {{{
> > diff --git a/include/uapi/linux/sysinfo.h b/include/uapi/linux/sysinfo.h
> > index 6e77e90..fe84c6a 100644
> > --- a/include/uapi/linux/sysinfo.h
> > +++ b/include/uapi/linux/sysinfo.h
> > @@ -12,7 +12,6 @@ struct sysinfo {
> > __kernel_ulong_t freeram; /* Available memory size */
> > __kernel_ulong_t sharedram; /* Amount of shared memory */
> > __kernel_ulong_t bufferram; /* Memory used by buffers */
> > - __kernel_ulong_t availram; /* Memory available for allocation */
> > __kernel_ulong_t totalswap; /* Total swap space size */
> > __kernel_ulong_t freeswap; /* swap space still available */
> > __u16 procs; /* Number of current processes */
> > @@ -20,7 +19,8 @@ struct sysinfo {
> > __kernel_ulong_t totalhigh; /* Total high memory size */
> > __kernel_ulong_t freehigh; /* Available high memory size */
> > __u32 mem_unit; /* Memory unit size in bytes */
> > - char _f[20-2*sizeof(__kernel_ulong_t)-sizeof(__u32)]; /*
> > Padding: libc5 uses this.. */
> > + __kernel_ulong_t availram; /* Memory available for allocation */
> > + char _f[20-3*sizeof(__kernel_ulong_t)-sizeof(__u32)]; /*
> > Padding: libc5 uses this.. */
> > };
> > }}}
> >
> > If this is fine, I will push the new patch set.
>
> Please CC linux-api@vger.kernel.org on the new posting.

That is probably still broken.
If __kernel_ulong_t is 64bit there is architecture
dependant padding after mem_unit.

In particular a 32bit x86 app running on a 64bit kernel
will probably see the wrong layout.

You definitely need a compile-time assert on the total structure size.

David

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