linux-kernel - Re: [PATCH v2 2/2] powerpc/fprobe: fix updated fprobe for function-graph tracer

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Message-ID: <12112eb1-3ece-4968-a277-4c035c7d0010@linux.ibm.com>
Date: Sat, 26 Jul 2025 19:45:43 +0530
From: Hari Bathini <hbathini@...ux.ibm.com>
To: Aditya Bodkhe <adityab1@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        maddy@...ux.ibm.com, mpe@...erman.id.au, npiggin@...il.com,
        christophe.leroy@...roup.eu, rostedt@...dmis.org, mhiramat@...nel.org,
        mark.rutland@....com, venkat88@...ux.ibm.com
Subject: Re: [PATCH v2 2/2] powerpc/fprobe: fix updated fprobe for
 function-graph tracer



On 22/07/25 2:26 pm, Aditya Bodkhe wrote:
> From: Hari Bathini <hbathini@...ux.ibm.com>
> 
> Since commit 4346ba160409 ("fprobe: Rewrite fprobe on function-graph
> tracer"), FPROBE depends on HAVE_FUNCTION_GRAPH_FREGS. With previous
> patch adding HAVE_FUNCTION_GRAPH_FREGS for powerpc, FPROBE can be
> enabled on powerpc. But with the commit b5fa903b7f7c ("fprobe: Add
> fprobe_header encoding feature"), asm/fprobe.h header is needed to
> define arch dependent encode/decode macros. The fprobe header MSB
> pattern on powerpc is not 0xf. So, define FPROBE_HEADER_MSB_PATTERN
> expected on powerpc.
> 
> Also, commit 762abbc0d09f ("fprobe: Use ftrace_regs in fprobe exit
> handler") introduced HAVE_FTRACE_REGS_HAVING_PT_REGS for archs that
> have pt_regs in ftrace_regs. Advertise that on powerpc to reuse
> common definitions like ftrace_partial_regs().
> 

Aditya, I assume there is no change on this patch from v1. I see
you missed the Acked-by tag from Masami while sending v2 though:

https://lore.kernel.org/all/20250609164700.d8afe4ac1b4dea195bb7e379@kernel.org/ 


> Signed-off-by: Hari Bathini <hbathini@...ux.ibm.com>
> Signed-off-by: Aditya Bodkhe <adityab1@...ux.ibm.com>
> ---
>   arch/powerpc/Kconfig              |  1 +
>   arch/powerpc/include/asm/fprobe.h | 12 ++++++++++++
>   2 files changed, 13 insertions(+)
>   create mode 100644 arch/powerpc/include/asm/fprobe.h
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 9163521bc4b9..2203e4fb64c1 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -246,6 +246,7 @@ config PPC
>   	select HAVE_EFFICIENT_UNALIGNED_ACCESS
>   	select HAVE_GUP_FAST
>   	select HAVE_FTRACE_GRAPH_FUNC
> +	select HAVE_FTRACE_REGS_HAVING_PT_REGS
>   	select HAVE_FTRACE_MCOUNT_RECORD
>   	select HAVE_FUNCTION_ARG_ACCESS_API
>   	select HAVE_FUNCTION_DESCRIPTORS	if PPC64_ELF_ABI_V1
> diff --git a/arch/powerpc/include/asm/fprobe.h b/arch/powerpc/include/asm/fprobe.h
> new file mode 100644
> index 000000000000..d64bc28fb3d3
> --- /dev/null
> +++ b/arch/powerpc/include/asm/fprobe.h
> @@ -0,0 +1,12 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_PPC_FPROBE_H
> +#define _ASM_PPC_FPROBE_H
> +
> +#include <asm-generic/fprobe.h>
> +
> +#ifdef CONFIG_64BIT
> +#undef FPROBE_HEADER_MSB_PATTERN
> +#define FPROBE_HEADER_MSB_PATTERN	(PAGE_OFFSET & ~FPROBE_HEADER_MSB_MASK)
> +#endif
> +
> +#endif /* _ASM_PPC_FPROBE_H */