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

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Message-ID: <CAHVXubiNh5B9COQOMtTr+kWvB=UzeVe7v87djYzVXT_Q+ffXiw@mail.gmail.com>
Date: Mon, 6 Jan 2025 10:57:51 +0100
From: Alexandre Ghiti <alexghiti@...osinc.com>
To: Clément Léger <cleger@...osinc.com>
Cc: 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
Subject: Re: [PATCH] riscv: use local label names instead of global ones in assembly

On Mon, Jan 6, 2025 at 10:36 AM Clément Léger <cleger@...osinc.com> wrote:
>
>
>
> 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.

No need to send a v2, b4 will pick the Fixes tag:

Fixes: 503638e0babf3 ("riscv: Stop emitting preventive sfence.vma for
new vmalloc mappings")

Thanks,

Alex

>
> 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
> >
>