linux-kernel - Re: [PATCH v2] csky: fix csky_cmpxchg

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Message-ID: <CA+N+=zsB=wd2G-nsYT9xxvsgBMtnOMUJb8ru8XHaqusX2nzzEg@mail.gmail.com>
Date: Fri, 18 Oct 2024 16:46:42 +0800
From: yang li <yang.li85200@...il.com>
To: Guo Ren <guoren@...nel.org>
Cc: linux-csky@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] csky: fix csky_cmpxchg_fixup not working

Hi Guo Ren:
I used the readelf tool to view the address of csky_cmpxchg_ldw,
and used printk("0x%x\n",csky_cmpxchg_ldw) and
printk("0x%x\n",&csky_cmpxchg_ldw) to print it out in the code.
 The result is that printk("0x%x\n",&csky_cmpxchg_ldw) prints the
correct result.

include/linux/linkage.h
#define GLOBAL(name)  \
        .globl name ASM_NL \
        name:
#endif

arch/csky/kernel/atomic.S:
GLOBAL(csky_cmpxchg_ldw)
so
.globl  csky_cmpxchg_ldw   --->globl symbol
csky_cmpxchg_ldw:             --->label symbol


yang li <yang.li85200@...il.com> 于2024年10月18日周五 16:33写道：
>
> Hi Guo Ren:
> I used the readelf tool to view the address of csky_cmpxchg_ldw,
> and used printk("0x%x\n",csky_cmpxchg_ldw) and
> printk("0x%x\n",&csky_cmpxchg_ldw) to print it out in the code.
>  The result is that printk("0x%x\n",&csky_cmpxchg_ldw) prints the
> correct result.
>
> include/linux/linkage.h
> #define GLOBAL(name)  \
>         .globl name ASM_NL \
>         name:
> #endif
>
> arch/csky/kernel/atomic.S:
> GLOBAL(csky_cmpxchg_ldw)
> so
> .globl  csky_cmpxchg_ldw   --->globl symbol
> csky_cmpxchg_ldw:             --->label symbol
>
>
>
>
> Guo Ren <guoren@...nel.org> 于2024年10月17日周四 14:05写道：
>>
>> On Wed, Oct 16, 2024 at 5:56 PM Yang Li <yang.li85200@...il.com> wrote:
>> >
>> > In the csky_cmpxchg_fixup function, it is incorrect to use the global
>> >  variable csky_cmpxchg_stw to determine the address where the exception
>> >  occurred.The global variable csky_cmpxchg_stw stores the opcode at the
>> >  time of the exception, while &csky_cmpxchg_stw shows the address where
>> >  the exception occurred.
>> >
>> > Signed-off-by: Yang Li <yang.li85200@...il.com>
>> > ---
>> > V1 -> V2:Eliminate compilation warnings
>> >
>> >  arch/csky/mm/fault.c | 4 ++--
>> >  1 file changed, 2 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/arch/csky/mm/fault.c b/arch/csky/mm/fault.c
>> > index a885518ce1dd..5226bc08c336 100644
>> > --- a/arch/csky/mm/fault.c
>> > +++ b/arch/csky/mm/fault.c
>> > @@ -45,8 +45,8 @@ static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
>> >         if (trap_no(regs) != VEC_TLBMODIFIED)
>> >                 return;
>> >
>> > -       if (instruction_pointer(regs) == csky_cmpxchg_stw)
>> > -               instruction_pointer_set(regs, csky_cmpxchg_ldw);
>> > +       if (instruction_pointer(regs) == (unsigned long)&csky_cmpxchg_stw)
>> > +               instruction_pointer_set(regs, (unsigned long)&csky_cmpxchg_ldw);
>> csky_cmpxchg_ldw(stw) is a label symbol, not a variable.
>>
>> arch/csky/kernel/atomic.S:
>> GLOBAL(csky_cmpxchg_ldw)
>> GLOBAL(csky_cmpxchg_stw)
>>
>> Your modification does not affect the ASM output.
>>
>> (gdb) p main
>> $1 = {void (void)} 0x5fa <main>
>> (gdb) p &main
>> $2 = (void (*)(void)) 0x5fa <main>
>>
>> >         return;
>> >  }
>> >  #endif
>> > --
>> > 2.34.1
>> >
>>
>>
>> --
>> Best Regards
>>  Guo Ren