linux-kernel - Re: [PATCH v2 2/5] riscv: Use SYM_*() assembly macros instead of deprecated ones

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Message-ID: <20231025-d21b7077ff99828bef7cfaa8@orel>
Date:   Wed, 25 Oct 2023 08:50:33 +0200
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Clément Léger <cleger@...osinc.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 2/5] riscv: Use SYM_*() assembly macros instead of
 deprecated ones

On Tue, Oct 24, 2023 at 08:03:52PM +0200, Clément Léger wrote:
> 
> 
> On 24/10/2023 17:23, Andrew Jones wrote:
> > On Tue, Oct 24, 2023 at 03:26:52PM +0200, Clément Léger wrote:
> > ...
> >> diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
> >> index 09b47ebacf2e..3ab438f30d13 100644
> >> --- a/arch/riscv/lib/uaccess.S
> >> +++ b/arch/riscv/lib/uaccess.S
> >> @@ -10,8 +10,7 @@
> >>  	_asm_extable	100b, \lbl
> >>  	.endm
> >>  
> >> -ENTRY(__asm_copy_to_user)
> >> -ENTRY(__asm_copy_from_user)
> >> +SYM_FUNC_START(__asm_copy_to_user)
> >>  
> >>  	/* Enable access to user memory */
> >>  	li t6, SR_SUM
> >> @@ -181,13 +180,13 @@ ENTRY(__asm_copy_from_user)
> >>  	csrc CSR_STATUS, t6
> >>  	sub a0, t5, a0
> >>  	ret
> >> -ENDPROC(__asm_copy_to_user)
> >> -ENDPROC(__asm_copy_from_user)
> >> +SYM_FUNC_END(__asm_copy_to_user)
> >>  EXPORT_SYMBOL(__asm_copy_to_user)
> >> +SYM_FUNC_ALIAS(__asm_copy_from_user, __asm_copy_to_user)
> >>  EXPORT_SYMBOL(__asm_copy_from_user)
> > 
> > I didn't see any comment about the sharing of debug info among both the
> > from and to functions. Assuming it isn't confusing in some way, then
> 
> Hi Andrew,
> 
> I did some testing with gdb and it seems to correctly assume that
> __asm_copy_to_user maps to __asm_copy_from_user for debugging. The basic
> tests that I did (breakpoints, disasm, etc) seems to show no sign of
> problems for debugging. Were you thinking about other things specifically ?

Mostly just backtrace symbols, but I suppose we can live with it, since
it wouldn't be the only weird thing in a backtrace.

Thanks,
drew