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From: Guo Ren <guoren@kernel.org>
Date: Sat, 23 Dec 2023 11:07:29 +0800
Message-ID: <CAJF2gTR7VvHhm4QUpEkk8P=b__HqbXZ7ggW9DvkD1fUpoKPTew@mail.gmail.com>
Subject: Re: [PATCH V3 1/4] riscv: mm: Fixup compat mode boot failure
To: Leonardo Bras <leobras@redhat.com>, charlie@rivosinc.com
Cc: linux-kernel@vger.kernel.org, paul.walmsley@sifive.com, palmer@dabbelt.com, 
	alexghiti@rivosinc.com, xiao.w.wang@intel.com, david@redhat.com, 
	panqinglin2020@iscas.ac.cn, rick.p.edgecombe@intel.com, willy@infradead.org, 
	bjorn@rivosinc.com, conor.dooley@microchip.com, cleger@rivosinc.com, 
	linux-riscv@lists.infradead.org, Guo Ren <guoren@linux.alibaba.com>, 
	stable@vger.kernel.org
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On Sat, Dec 23, 2023 at 10:58=E2=80=AFAM Leonardo Bras <leobras@redhat.com>=
 wrote:
>
> On Fri, Dec 22, 2023 at 06:57:00AM -0500, guoren@kernel.org wrote:
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > In COMPAT mode, the STACK_TOP is DEFAULT_MAP_WINDOW (0x80000000), but
> > the TASK_SIZE is 0x7fff000. When the user stack is upon 0x7fff000, it
> > will cause a user segment fault. Sometimes, it would cause boot
> > failure when the whole rootfs is rv32.
> >
> > Freeing unused kernel image (initmem) memory: 2236K
> > Run /sbin/init as init process
> > Starting init: /sbin/init exists but couldn't execute it (error -14)
> > Run /etc/init as init process
> > ...
> >
> > Increase the TASK_SIZE to cover STACK_TOP.
> >
> > Cc: stable@vger.kernel.org
> > Fixes: add2cc6b6515 ("RISC-V: mm: Restrict address space for sv39,sv48,=
sv57")
> > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > Signed-off-by: Guo Ren <guoren@kernel.org>
> > ---
> >  arch/riscv/include/asm/pgtable.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/=
pgtable.h
> > index ab00235b018f..74ffb2178f54 100644
> > --- a/arch/riscv/include/asm/pgtable.h
> > +++ b/arch/riscv/include/asm/pgtable.h
> > @@ -881,7 +881,7 @@ static inline pte_t pte_swp_clear_exclusive(pte_t p=
te)
> >  #define TASK_SIZE_MIN        (PGDIR_SIZE_L3 * PTRS_PER_PGD / 2)
> >
> >  #ifdef CONFIG_COMPAT
> > -#define TASK_SIZE_32 (_AC(0x80000000, UL) - PAGE_SIZE)
> > +#define TASK_SIZE_32 (_AC(0x80000000, UL))
> >  #define TASK_SIZE    (test_thread_flag(TIF_32BIT) ? \
> >                        TASK_SIZE_32 : TASK_SIZE_64)
> >  #else
> > --
> > 2.40.1
> >
>
> I am not really involved in the issue this is solving, so I have no
> technical opinion on the solution.
>
> IIUC there should always be (TASK_SIZE >=3D STACK_TOP), so by itself this
> is fixing an issue.
>
> I have reviewed the code and it does exactly as stated into the commit
> message, so FWIW:
> Reviewed-by: Leonardo Bras <leobras@redhat.com>
Thx,

I found this problem because it can't boot my rv32 buildroot-rootfs in
v6.6. But it's okay in v6.5. So I used git bisect and found commit:
add2cc6b6515 ("RISC-V: mm: Restrict address space for
sv39,sv48,sv57"), which caused that.

Ping Charlie, I hope it can be fixed in the v6.6 long-term version.

>


--
Best Regards
 Guo Ren