linux-kernel - Re: [PATCH] riscv: use local label names instead of global ones in assembly

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Message-ID: <4f78a39a-0788-49a4-9d63-777bb9d15b30@rivosinc.com>
Date: Mon, 6 Jan 2025 10:35:56 +0100
From: Clément Léger <cleger@...osinc.com>
To: Alexandre Ghiti <alex@...ti.fr>, Paul Walmsley
 <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: Alexandre Ghiti <alexghiti@...osinc.com>
Subject: Re: [PATCH] riscv: use local label names instead of global ones in
 assembly



On 06/01/2025 09:52, Alexandre Ghiti wrote:
> Hi Clément,
> 
> On 03/01/2025 15:17, Clément Léger wrote:
>> Local labels should be prefix by '.L' or they'll be exported in the
>> symbol table. Additionally, this messes up the backtrace by displaying
>> an incorrect symbol:
>>
>>    ...
>>    [   12.751810] [<ffffffff80441628>] _copy_from_user+0x28/0xc2
>>    [   12.752035] [<ffffffff800152ca>] handle_misaligned_load+0x1ca/0x2fc
>>    [   12.752310] [<ffffffff80a033e8>] do_trap_load_misaligned+0x24/0xee
>>    [   12.752596] [<ffffffff80a0dcae>]
>> _new_vmalloc_restore_context_a0+0xc2/0xce
> 
> 
> Yes, I noticed this last week, thanks for looking into it. I would add a
> Fixes tag and merge that in the next -rc if possible as the above
> backtrace is "disturbing".

Hi Alex,

Yeah, I thought the Fixes tag, but since it wasn't really "breaking"
anything, I left it out. I'll add it and sent a V2.

Thanks

Clément

> 
> 
>>
>> After:
>>    ...
>>    [   10.243916] [<ffffffff804415e4>] _copy_from_user+0x28/0xc2
>>    [   10.244026] [<ffffffff800152ca>] handle_misaligned_load+0x1ca/0x2fc
>>    [   10.244150] [<ffffffff80a033a0>] do_trap_load_misaligned+0x24/0xee
>>    [   10.244268] [<ffffffff80a0dc66>] handle_exception+0x146/0x152
>>
>> Signed-off-by: Clément Léger <cleger@...osinc.com>
>>
>> ---
>>   arch/riscv/kernel/entry.S | 20 ++++++++++----------
>>   1 file changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
>> index c200d329d4bd..216581835eb0 100644
>> --- a/arch/riscv/kernel/entry.S
>> +++ b/arch/riscv/kernel/entry.S
>> @@ -23,21 +23,21 @@
>>       REG_S     a0, TASK_TI_A0(tp)
>>       csrr     a0, CSR_CAUSE
>>       /* Exclude IRQs */
>> -    blt      a0, zero, _new_vmalloc_restore_context_a0
>> +    blt      a0, zero, .Lnew_vmalloc_restore_context_a0
>>         REG_S     a1, TASK_TI_A1(tp)
>>       /* Only check new_vmalloc if we are in page/protection fault */
>>       li       a1, EXC_LOAD_PAGE_FAULT
>> -    beq      a0, a1, _new_vmalloc_kernel_address
>> +    beq      a0, a1, .Lnew_vmalloc_kernel_address
>>       li       a1, EXC_STORE_PAGE_FAULT
>> -    beq      a0, a1, _new_vmalloc_kernel_address
>> +    beq      a0, a1, .Lnew_vmalloc_kernel_address
>>       li       a1, EXC_INST_PAGE_FAULT
>> -    bne      a0, a1, _new_vmalloc_restore_context_a1
>> +    bne      a0, a1, .Lnew_vmalloc_restore_context_a1
>>   -_new_vmalloc_kernel_address:
>> +.Lnew_vmalloc_kernel_address:
>>       /* Is it a kernel address? */
>>       csrr     a0, CSR_TVAL
>> -    bge     a0, zero, _new_vmalloc_restore_context_a1
>> +    bge     a0, zero, .Lnew_vmalloc_restore_context_a1
>>         /* Check if a new vmalloc mapping appeared that could explain
>> the trap */
>>       REG_S    a2, TASK_TI_A2(tp)
>> @@ -69,7 +69,7 @@ _new_vmalloc_kernel_address:
>>       /* Check the value of new_vmalloc for this cpu */
>>       REG_L    a2, 0(a0)
>>       and    a2, a2, a1
>> -    beq    a2, zero, _new_vmalloc_restore_context
>> +    beq    a2, zero, .Lnew_vmalloc_restore_context
>>         /* Atomically reset the current cpu bit in new_vmalloc */
>>       amoxor.d    a0, a1, (a0)
>> @@ -83,11 +83,11 @@ _new_vmalloc_kernel_address:
>>       csrw    CSR_SCRATCH, x0
>>       sret
>>   -_new_vmalloc_restore_context:
>> +.Lnew_vmalloc_restore_context:
>>       REG_L     a2, TASK_TI_A2(tp)
>> -_new_vmalloc_restore_context_a1:
>> +.Lnew_vmalloc_restore_context_a1:
>>       REG_L     a1, TASK_TI_A1(tp)
>> -_new_vmalloc_restore_context_a0:
>> +.Lnew_vmalloc_restore_context_a0:
>>       REG_L    a0, TASK_TI_A0(tp)
>>   .endm
>>   
> 
> 
> You can add:
> 
> Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>
> 
> Thanks,
> 
> Alex
>