Re: [PATCH v18 12/17] fprobe: Add fprobe_header encoding feature

Steven Rostedt
2024-11-01T14:21:18Z

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

> From: Masami Hiramatsu (Google) <mhiramat@kernel.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@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Huacai Chen <chenhuacai@kernel.org>
> Cc: WANG Xuerui <kernel@xen0n.name>
> Cc: Paul Walmsley <paul.walmsley@sifive.com>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Albert Ou <aou@eecs.berkeley.edu>
> Cc: Heiko Carstens <hca@linux.ibm.com>
> Cc: Vasily Gorbik <gor@linux.ibm.com>
> Cc: Alexander Gordeev <agordeev@linux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
> Cc: Sven Schnelle <svens@linux.ibm.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: x86@kernel.org
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.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