linux-kernel - Re: [PATCH 3/4] sparc: fix accurate exception reporting in copy_{from_to}

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Message-ID: <90082c61c8bee761b1a57070e2755bbc8a812cd9.camel@physik.fu-berlin.de>
Date: Fri, 29 Aug 2025 23:44:15 +0200
From: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To: Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>, 
	linux-kernel@...r.kernel.org
Cc: sparclinux@...r.kernel.org, Andreas Larsson <andreas@...sler.com>, 
 Anthony Yznaga <anthony.yznaga@...cle.com>
Subject: Re: [PATCH 3/4] sparc: fix accurate exception reporting in
 copy_{from_to}_user for Niagara

Hello,

On Tue, 2025-08-26 at 18:03 +0200, Michael Karcher wrote:
> Fixes: 7ae3aaf53f16 ("sparc64: Convert NGcopy_{from,to}_user to accurate exception reporting.")
> Signed-off-by: Michael Karcher <kernel@...rcher.dialup.fu-berlin.de>
> ---
>  arch/sparc/lib/NGmemcpy.S | 29 ++++++++++++++++++-----------
>  1 file changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/sparc/lib/NGmemcpy.S b/arch/sparc/lib/NGmemcpy.S
> index ee51c1230689..bbd3ea0a6482 100644
> --- a/arch/sparc/lib/NGmemcpy.S
> +++ b/arch/sparc/lib/NGmemcpy.S
> @@ -79,8 +79,8 @@
>  #ifndef EX_RETVAL
>  #define EX_RETVAL(x)	x
>  __restore_asi:
> -	ret
>  	wr	%g0, ASI_AIUS, %asi
> +	ret
>  	 restore
>  ENTRY(NG_ret_i2_plus_i4_plus_1)
>  	ba,pt	%xcc, __restore_asi
> @@ -125,15 +125,16 @@ ENTRY(NG_ret_i2_plus_g1_minus_56)
>  	ba,pt	%xcc, __restore_asi
>  	 add	%i2, %g1, %i0
>  ENDPROC(NG_ret_i2_plus_g1_minus_56)
> -ENTRY(NG_ret_i2_plus_i4)
> +ENTRY(NG_ret_i2_plus_i4_plus_16)
> +        add     %i4, 16, %i4
>  	ba,pt	%xcc, __restore_asi
>  	 add	%i2, %i4, %i0
> -ENDPROC(NG_ret_i2_plus_i4)
> -ENTRY(NG_ret_i2_plus_i4_minus_8)
> -	sub	%i4, 8, %i4
> +ENDPROC(NG_ret_i2_plus_i4_plus_16)
> +ENTRY(NG_ret_i2_plus_i4_plus_8)
> +	add	%i4, 8, %i4
>  	ba,pt	%xcc, __restore_asi
>  	 add	%i2, %i4, %i0
> -ENDPROC(NG_ret_i2_plus_i4_minus_8)
> +ENDPROC(NG_ret_i2_plus_i4_plus_8)
>  ENTRY(NG_ret_i2_plus_8)
>  	ba,pt	%xcc, __restore_asi
>  	 add	%i2, 8, %i0
> @@ -160,6 +161,12 @@ ENTRY(NG_ret_i2_and_7_plus_i4)
>  	ba,pt	%xcc, __restore_asi
>  	 add	%i2, %i4, %i0
>  ENDPROC(NG_ret_i2_and_7_plus_i4)
> +ENTRY(NG_ret_i2_and_7_plus_i4_plus_8)
> +	and	%i2, 7, %i2
> +	add	%i4, 8, %i4
> +	ba,pt	%xcc, __restore_asi
> +	 add	%i2, %i4, %i0
> +ENDPROC(NG_ret_i2_and_7_plus_i4)
>  #endif
>  
>  	.align		64
> @@ -405,13 +412,13 @@ FUNC_NAME:	/* %i0=dst, %i1=src, %i2=len */
>  	andn		%i2, 0xf, %i4
>  	and		%i2, 0xf, %i2
>  1:	subcc		%i4, 0x10, %i4
> -	EX_LD(LOAD(ldx, %i1, %o4), NG_ret_i2_plus_i4)
> +	EX_LD(LOAD(ldx, %i1, %o4), NG_ret_i2_plus_i4_plus_16)
>  	add		%i1, 0x08, %i1
> -	EX_LD(LOAD(ldx, %i1, %g1), NG_ret_i2_plus_i4)
> +	EX_LD(LOAD(ldx, %i1, %g1), NG_ret_i2_plus_i4_plus_16)
>  	sub		%i1, 0x08, %i1
> -	EX_ST(STORE(stx, %o4, %i1 + %i3), NG_ret_i2_plus_i4)
> +	EX_ST(STORE(stx, %o4, %i1 + %i3), NG_ret_i2_plus_i4_plus_16)
>  	add		%i1, 0x8, %i1
> -	EX_ST(STORE(stx, %g1, %i1 + %i3), NG_ret_i2_plus_i4_minus_8)
> +	EX_ST(STORE(stx, %g1, %i1 + %i3), NG_ret_i2_plus_i4_plus_8)
>  	bgu,pt		%XCC, 1b
>  	 add		%i1, 0x8, %i1
>  73:	andcc		%i2, 0x8, %g0
> @@ -468,7 +475,7 @@ FUNC_NAME:	/* %i0=dst, %i1=src, %i2=len */
>  	subcc		%i4, 0x8, %i4
>  	srlx		%g3, %i3, %i5
>  	or		%i5, %g2, %i5
> -	EX_ST(STORE(stx, %i5, %o0), NG_ret_i2_and_7_plus_i4)
> +	EX_ST(STORE(stx, %i5, %o0), NG_ret_i2_and_7_plus_i4_plus_8)
>  	add		%o0, 0x8, %o0
>  	bgu,pt		%icc, 1b
>  	 sllx		%g3, %g1, %g2

Verified on a SPARC T4 with the following hack applied:

diff --git a/arch/sparc/kernel/head_64.S b/arch/sparc/kernel/head_64.S
index cf0549134234..886cb8932a0b 100644
--- a/arch/sparc/kernel/head_64.S
+++ b/arch/sparc/kernel/head_64.S
@@ -635,7 +635,7 @@ sparc_m7_patch:
         nop
 
 niagara4_patch:
-       call    niagara4_patch_copyops
+       call    niagara_patch_copyops
         nop
        call    niagara4_patch_bzero
         nop

Kernel is stable and does not produce any backtraces. Should still be
tested on a real SPARC T1 if possible though.

Tested-by: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
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