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

Masami Hiramatsu
2024-11-09T15:11:03Z

On Fri, 1 Nov 2024 10:22:12 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> 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

OK.

>
>
> > 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.

OK, but x86 and riscv, we need this default template on 64bit only.
So those may keep it, right?

Thank you,

>
> -- Steve

--
Masami Hiramatsu (Google) <mhiramat@kernel.org>