linux-kernel - Re: [PATCH v1 2/4] powerpc/ftrace: Refactor ftrace_{regs

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Message-Id: <1646326634.jzerx009p9.naveen@linux.ibm.com>
Date:   Thu, 03 Mar 2022 22:29:50 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v1 2/4] powerpc/ftrace: Refactor ftrace_{regs_}caller

Christophe Leroy wrote:
> ftrace_caller() and frace_regs_caller() have now a lot in common.
> 
> Refactor them using GAS macros.

Thanks for doing this - this looks much better.

> 
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  arch/powerpc/kernel/trace/ftrace_mprofile.S | 147 ++++++--------------
>  1 file changed, 45 insertions(+), 102 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/trace/ftrace_mprofile.S b/arch/powerpc/kernel/trace/ftrace_mprofile.S
> index 76dab07fd8fd..630b2de9957b 100644
> --- a/arch/powerpc/kernel/trace/ftrace_mprofile.S
> +++ b/arch/powerpc/kernel/trace/ftrace_mprofile.S
> @@ -32,7 +32,7 @@
>   * Our job is to save the register state into a struct pt_regs (on the stack)
>   * and then arrange for the ftrace function to be called.
>   */
> -_GLOBAL(ftrace_regs_caller)
> +.macro	ftrace_regs_entry allregs
>  	/* Save the original return address in A's stack frame */
>  #ifdef CONFIG_MPROFILE_KERNEL
>  	PPC_STL	r0,LRSAVE(r1)
> @@ -43,7 +43,7 @@ _GLOBAL(ftrace_regs_caller)
> 
>  	/* Save all gprs to pt_regs */
>  	SAVE_GPR(0, r1)
> -	SAVE_GPRS(2, 11, r1)
> +	SAVE_GPRS(3, 10, r1)
> 
>  #ifdef CONFIG_PPC64
>  	/* Ok to continue? */
> @@ -52,17 +52,29 @@ _GLOBAL(ftrace_regs_caller)
>  	beq	ftrace_no_trace
>  #endif

The ability to disable ftrace in certain code paths through 
paca_struct->ftrace_enabled will also be relevant on ppc32 - it will be 
nice if it can be introduced there.

For this series though:
Reviewed-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>


- Naveen