Re: [patch -v2] flat: fix data sections alignment
From: Johannes Weiner
Date: Thu Mar 05 2009 - 05:55:05 EST
On Wed, Mar 04, 2009 at 04:48:04PM -0500, Mike Frysinger wrote:
> On Wed, Mar 4, 2009 at 08:51, Johannes Weiner wrote:
> > --- a/fs/binfmt_flat.c
> > +++ b/fs/binfmt_flat.c
> > +#ifdef ARCH_SLAB_MINALIGN
> > +#define FLAT_DATA_ALIGN (ARCH_SLAB_MINALIGN)
> > +#else
> > +#define FLAT_DATA_ALIGN (sizeof(void *))
> > +#endif
> > ...
> > + sp = (unsigned long *) ((unsigned long)sp & -FLAT_DATA_ALIGN);
> > ...
> > - datapos = realdatastart + MAX_SHARED_LIBS * sizeof(unsigned long);
> > + datapos = ALIGN(realdatastart + MAX_SHARED_LIBS * sizeof(unsigned long),
> > + FLAT_DATA_ALIGN);
> > ...
> > - datapos = realdatastart + MAX_SHARED_LIBS * sizeof(unsigned long);
> > + datapos = ALIGN(realdatastart + MAX_SHARED_LIBS * sizeof(unsigned long),
> > + FLAT_DATA_ALIGN);
>
> why not make FLAT_DATA_ALIGN into a macro ? then it'd naturally
> follow the existing ALIGN() behavior.
datapos is aligned to the next higher bound while the stack pointer
grows down and is therefor aligned to the next lower bound. A
FLAT_DATA_ALIGN() doesn't make sense.
> > - sp = (unsigned long *) ((-(unsigned long)sizeof(char *))&(unsigned long) p);
> > -
> > - sp -= envc+1;
> > - envp = sp;
> > - sp -= argc+1;
> > - argv = sp;
> > + sp = (unsigned long *)p;
> > + sp -= (envc + argc + 2) + 1 + (flat_argvp_envp_on_stack() ? 2 : 0);
> > + sp = (unsigned long *) ((unsigned long)sp & -FLAT_DATA_ALIGN);
> > + argv = sp + 1 + (flat_argvp_envp_on_stack() ? 2 : 0);
> > + envp = argv + (argc + 1);
Hannes
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