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

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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
.




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