linux-kernel - Re: [PATCH v18 12/17] fprobe: Add fprobe

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Message-ID: <20241101102212.5e9d74d9@gandalf.local.home>
Date: Fri, 1 Nov 2024 10:22:12 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>, Florent Revest
 <revest@...omium.org>, linux-trace-kernel@...r.kernel.org, LKML
 <linux-kernel@...r.kernel.org>, Martin KaFai Lau <martin.lau@...ux.dev>,
 bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, Jiri Olsa
 <jolsa@...nel.org>, Alan Maguire <alan.maguire@...cle.com>, Mark Rutland
 <mark.rutland@....com>, linux-arch@...r.kernel.org, Catalin Marinas
 <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Huacai Chen
 <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>, Paul Walmsley
 <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou
 <aou@...s.berkeley.edu>, Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik
 <gor@...ux.ibm.com>, Alexander Gordeev <agordeev@...ux.ibm.com>, Christian
 Borntraeger <borntraeger@...ux.ibm.com>, Sven Schnelle
 <svens@...ux.ibm.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar
 <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
 <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin"
 <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH v18 12/17] fprobe: Add fprobe_header encoding feature

On Sat, 26 Oct 2024 13:37:59 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Fprobe store its data structure address and size on the fgraph return stack
> by __fprobe_header. But most 64bit architecture can combine those to
> one unsigned long value because 4 MSB in the kernel address are the same.
> With this encoding, fprobe can consume less space on ret_stack.
> 
> This introduces asm/fprobe.h to define arch dependent encode/decode
> macros. Note that since fprobe depends on CONFIG_HAVE_FUNCTION_GRAPH_FREGS,
> currently only arm64, loongarch, riscv, s390 and x86 are supported.
> 
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Huacai Chen <chenhuacai@...nel.org>
> Cc: WANG Xuerui <kernel@...0n.name>
> Cc: Paul Walmsley <paul.walmsley@...ive.com>
> Cc: Palmer Dabbelt <palmer@...belt.com>
> Cc: Albert Ou <aou@...s.berkeley.edu>
> Cc: Heiko Carstens <hca@...ux.ibm.com>
> Cc: Vasily Gorbik <gor@...ux.ibm.com>
> Cc: Alexander Gordeev <agordeev@...ux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@...ux.ibm.com>
> Cc: Sven Schnelle <svens@...ux.ibm.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: x86@...nel.org
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> ---
>  arch/arm64/include/asm/fprobe.h     |    7 +++++++
>  arch/loongarch/include/asm/fprobe.h |    5 +++++
>  arch/riscv/include/asm/fprobe.h     |    9 +++++++++
>  arch/s390/include/asm/fprobe.h      |   10 ++++++++++
>  arch/x86/include/asm/fprobe.h       |    9 +++++++++
>  include/asm-generic/fprobe.h        |   33 +++++++++++++++++++++++++++++++++
>  kernel/trace/fprobe.c               |   29 +++++++++++++++++++++++++++++
>  7 files changed, 102 insertions(+)
>  create mode 100644 arch/arm64/include/asm/fprobe.h
>  create mode 100644 arch/loongarch/include/asm/fprobe.h
>  create mode 100644 arch/riscv/include/asm/fprobe.h
>  create mode 100644 arch/s390/include/asm/fprobe.h
>  create mode 100644 arch/x86/include/asm/fprobe.h
>  create mode 100644 include/asm-generic/fprobe.h
> 
> diff --git a/arch/arm64/include/asm/fprobe.h b/arch/arm64/include/asm/fprobe.h
> new file mode 100644
> index 000000000000..bbf254db878d
> --- /dev/null
> +++ b/arch/arm64/include/asm/fprobe.h
> @@ -0,0 +1,7 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_ARM64_FPROBE_H
> +#define _ASM_ARM64_FPROBE_H
> +
> +#include <asm-generic/fprobe.h>
> +
> +#endif /* _ASM_ARM64_FPROBE_H */
> \ No newline at end of file

This isn't the way to add asm-generic code to architectures. It needs to be
in the Kbuild file. Like this:

diff --git a/arch/arm64/include/asm/Kbuild b/arch/arm64/include/asm/Kbuild
index 4e350df9a02d..0d0a638d41a8 100644
--- a/arch/arm64/include/asm/Kbuild
+++ b/arch/arm64/include/asm/Kbuild
@@ -14,6 +14,7 @@ generic-y += qrwlock.h
 generic-y += qspinlock.h
 generic-y += parport.h
 generic-y += user.h
+generic-y += fprobe.h
 
 generated-y += cpucap-defs.h
 generated-y += sysreg-defs.h


> diff --git a/arch/loongarch/include/asm/fprobe.h b/arch/loongarch/include/asm/fprobe.h
> new file mode 100644
> index 000000000000..68156a66873c
> --- /dev/null
> +++ b/arch/loongarch/include/asm/fprobe.h
> @@ -0,0 +1,5 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_LOONGARCH_FPROBE_H
> +#define _ASM_LOONGARCH_FPROBE_H
> +
> +#endif /* _ASM_LOONGARCH_FPROBE_H */
> \ No newline at end of file
> diff --git a/arch/riscv/include/asm/fprobe.h b/arch/riscv/include/asm/fprobe.h
> new file mode 100644
> index 000000000000..51fc2ef3eda1
> --- /dev/null
> +++ b/arch/riscv/include/asm/fprobe.h
> @@ -0,0 +1,9 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_RISCV_FPROBE_H
> +#define _ASM_RISCV_FPROBE_H
> +
> +#ifdef CONFIG_64BIT
> +#include <asm-generic/fprobe.h>
> +#endif
> +
> +#endif /* _ASM_RISCV_FPROBE_H */
> \ No newline at end of file
> diff --git a/arch/s390/include/asm/fprobe.h b/arch/s390/include/asm/fprobe.h
> new file mode 100644
> index 000000000000..84b94ba6e3a4
> --- /dev/null
> +++ b/arch/s390/include/asm/fprobe.h
> @@ -0,0 +1,10 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_S390_FPROBE_H
> +#define _ASM_S390_FPROBE_H
> +
> +#include <asm-generic/fprobe.h>
> +
> +#undef FPROBE_HEADER_MSB_PATTERN
> +#define FPROBE_HEADER_MSB_PATTERN 0
> +
> +#endif /* _ASM_S390_FPROBE_H */
> \ No newline at end of file
> diff --git a/arch/x86/include/asm/fprobe.h b/arch/x86/include/asm/fprobe.h
> new file mode 100644
> index 000000000000..c863518bef90
> --- /dev/null
> +++ b/arch/x86/include/asm/fprobe.h
> @@ -0,0 +1,9 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_X86_FPROBE_H
> +#define _ASM_X86_FPROBE_H
> +
> +#ifdef CONFIG_64BIT
> +#include <asm-generic/fprobe.h>
> +#endif
> +
> +#endif /* _ASM_X86_FPROBE_H */
> \ No newline at end of file

Same for the above.

-- Steve