Re: [PATCH v2 00/15] init_mm: cleanup ARCH's text/data/brk setup code

[Kefeng Wang]

On 2021/6/7 13:48, Christophe Leroy wrote:
> Hi Kefeng,
>
> Le 07/06/2021 à 02:55, Kefeng Wang a écrit :
> > On 2021/6/7 5:29, Mike Rapoport wrote:
> > > Hello Kefeng,
> > >
> > > On Fri, Jun 04, 2021 at 03:06:18PM +0800, Kefeng Wang wrote:
> > > > Add setup_initial_init_mm() helper, then use it
> > > > to cleanup the text, data and brk setup code.
> > > >
> > > > v2:
> > > > - change argument from "char *" to "void *" setup_initial_init_mm()
> > > >    suggested by Geert Uytterhoeven
> > > > - use NULL instead of (void *)0 on h8300 and m68k
> > > > - collect ACKs
> > > >
> > > > Cc: linux-snps-arc@xxxxxxxxxxxxxxxxxxx
> > > > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > > > Cc: linux-csky@xxxxxxxxxxxxxxx
> > > > Cc: uclinux-h8-devel@xxxxxxxxxxxxxxxxxxxx
> > > > Cc: linux-m68k@xxxxxxxxxxxxxxxxxxxx
> > > > Cc: openrisc@xxxxxxxxxxxxxxxxxxxx
> > > > Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> > > > Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx
> > > > Cc: linux-sh@xxxxxxxxxxxxxxx
> > > > Cc: linux-s390@xxxxxxxxxxxxxxx
> > > > Kefeng Wang (15):
> > > >    mm: add setup_initial_init_mm() helper
> > > >    arc: convert to setup_initial_init_mm()
> > > >    arm: convert to setup_initial_init_mm()
> > > >    arm64: convert to setup_initial_init_mm()
> > > >    csky: convert to setup_initial_init_mm()
> > > >    h8300: convert to setup_initial_init_mm()
> > > >    m68k: convert to setup_initial_init_mm()
> > > >    nds32: convert to setup_initial_init_mm()
> > > >    nios2: convert to setup_initial_init_mm()
> > > >    openrisc: convert to setup_initial_init_mm()
> > > >    powerpc: convert to setup_initial_init_mm()
> > > >    riscv: convert to setup_initial_init_mm()
> > > >    s390: convert to setup_initial_init_mm()
> > > >    sh: convert to setup_initial_init_mm()
> > > >    x86: convert to setup_initial_init_mm()
> > > I might be missing something, but AFAIU the init_mm.start_code and 
> > > other
> > > fields are not used really early so the new setup_initial_init_mm()
> > > function can be called in the generic code outside setup_arch(), e.g in
> > > mm_init().
> >
> > Hi Mike， each architecture has their own value, not the same, eg m68K 
> > and
> >
> > h8300, also the name of the text/code/brk is different in some arch, 
> > so I keep
> >
> > unchanged.
>
> What you could do is to define a __weak function that architectures 
> can override and call that function from mm_init() as suggested by Mike,
>
> Something like:
>
> void __weak setup_initial_init_mm(void)
> {
>     init_mm.start_code = (unsigned long)_stext;
>     init_mm.end_code = (unsigned long)_etext;
>     init_mm.end_data = (unsigned long)_edata;
>     init_mm.brk = (unsigned long)_end;
> }
>
> Then only the few architecture that are different would override it.
>
> I see a few archictectures are usigne PAGE_OFFSET to set .start_code, 
> but it is likely that this is equivalent to _stext.


Yes,  the __weak function is option, but the change is only covered 14 
archs, there are 7 other archs（alpha  hexagon  ia64

microblaze  mips sparc  um xtensa）without related setup code. Also like 
x86, it has own brk , maybe there are some

other different in some arch, so I think let's keep unchanged for now,  
thanks.

> Christophe
> .