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From: Bagas Sanjaya <bagasdotme@gmail.com>
To: "Björn Töpel" <bjorn@kernel.org>,
	"Andy Chiu" <andybnac@gmail.com>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Masami Hiramatsu" <mhiramat@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	"Robbin Ehn" <rehn@rivosinc.com>
Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org, bjorn@rivosinc.com,
	puranjay12@gmail.com, alexghiti@rivosinc.com,
	yongxuan.wang@sifive.com, greentime.hu@sifive.com,
	nick.hu@sifive.com, nylon.chen@sifive.com, tommy.wu@sifive.com,
	eric.lin@sifive.com, viccent.chen@sifive.com, zong.li@sifive.com,
	samuel.holland@sifive.com
Subject: Re: [PATCH v3 3/7] riscv: ftrace: prepare ftrace for atomic code patching
Date: Sat, 7 Dec 2024 06:35:27 +0700	[thread overview]
Message-ID: <Z1OKPxHBJ0kV5TbA@archie.me> (raw)
In-Reply-To: <87v7vxf7t6.fsf@all.your.base.are.belong.to.us>


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On Fri, Dec 06, 2024 at 11:02:29AM +0100, Björn Töpel wrote:
> Adding Robbin for input, who's doing much more crazy text patching in
> JVM, than what we do in the kernel. ;-)
> 
> Let's say we're tracing "f". Previously w/ stop_machine() it was
> something like:
> 
> f:
> 1: nop
>    nop
>    ...
>    ...
> 
> ftrace_caller:
>    ...
>    auipc	a2, function_trace_op
>    ld		a2, function_trace_op(a2)
>    ...
> 2: auipc    ra, ftrace_stub
>    jalr     ftrace_stub(ra)
> 
> The text was patched by ftrace in 1 and 2.
> 
> ...and now:
> f:
>    auipc    t0, ftrace_caller
> A: nop
>    ...
>    ...
> 
> ftrace_caller:
>    ...
>    auipc    a2, function_trace_op
>    ld       a2, function_trace_op(a2)
>    ...
>    auipc    ra, ftrace_call_dest
>    ld       ra, ftrace_call_dest(ra)
>    jalr     ra 
> 
> The text is only patched in A, and the tracer func is loaded via
> ftrace_call_dest.

Previously the operation was no-op, right?

Confused...

-- 
An old man doll... just what I always wanted! - Clara

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WARNING: multiple messages have this Message-ID (diff)
From: Bagas Sanjaya <bagasdotme@gmail.com>
To: "Björn Töpel" <bjorn@kernel.org>,
	"Andy Chiu" <andybnac@gmail.com>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Masami Hiramatsu" <mhiramat@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	"Robbin Ehn" <rehn@rivosinc.com>
Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org, bjorn@rivosinc.com,
	puranjay12@gmail.com, alexghiti@rivosinc.com,
	yongxuan.wang@sifive.com, greentime.hu@sifive.com,
	nick.hu@sifive.com, nylon.chen@sifive.com, tommy.wu@sifive.com,
	eric.lin@sifive.com, viccent.chen@sifive.com, zong.li@sifive.com,
	samuel.holland@sifive.com
Subject: Re: [PATCH v3 3/7] riscv: ftrace: prepare ftrace for atomic code patching
Date: Sat, 7 Dec 2024 06:35:27 +0700	[thread overview]
Message-ID: <Z1OKPxHBJ0kV5TbA@archie.me> (raw)
In-Reply-To: <87v7vxf7t6.fsf@all.your.base.are.belong.to.us>

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On Fri, Dec 06, 2024 at 11:02:29AM +0100, Björn Töpel wrote:
> Adding Robbin for input, who's doing much more crazy text patching in
> JVM, than what we do in the kernel. ;-)
> 
> Let's say we're tracing "f". Previously w/ stop_machine() it was
> something like:
> 
> f:
> 1: nop
>    nop
>    ...
>    ...
> 
> ftrace_caller:
>    ...
>    auipc	a2, function_trace_op
>    ld		a2, function_trace_op(a2)
>    ...
> 2: auipc    ra, ftrace_stub
>    jalr     ftrace_stub(ra)
> 
> The text was patched by ftrace in 1 and 2.
> 
> ...and now:
> f:
>    auipc    t0, ftrace_caller
> A: nop
>    ...
>    ...
> 
> ftrace_caller:
>    ...
>    auipc    a2, function_trace_op
>    ld       a2, function_trace_op(a2)
>    ...
>    auipc    ra, ftrace_call_dest
>    ld       ra, ftrace_call_dest(ra)
>    jalr     ra 
> 
> The text is only patched in A, and the tracer func is loaded via
> ftrace_call_dest.

Previously the operation was no-op, right?

Confused...

-- 
An old man doll... just what I always wanted! - Clara

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  reply	other threads:[~2024-12-06 23:35 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-11-27 17:29 [PATCH v3 0/7] riscv: ftrace: atmoic patching and preempt improvements Andy Chiu
2024-11-27 17:29 ` Andy Chiu
2024-11-27 17:29 ` [PATCH v3 1/7] riscv: ftrace: support fastcc in Clang for WITH_ARGS Andy Chiu
2024-11-27 17:29   ` Andy Chiu
2024-12-03 12:05   ` Björn Töpel
2024-12-03 12:05     ` Björn Töpel
2024-12-03 14:44     ` Evgenii Shatokhin
2024-12-03 14:44       ` Evgenii Shatokhin
2024-11-27 17:29 ` [PATCH v3 2/7] riscv: ftrace: align patchable functions to 4 Byte boundary Andy Chiu
2024-11-27 17:29   ` Andy Chiu
2024-11-27 17:29 ` [PATCH v3 3/7] riscv: ftrace: prepare ftrace for atomic code patching Andy Chiu
2024-11-27 17:29   ` Andy Chiu
2024-12-01 15:31   ` Evgenii Shatokhin
2024-12-01 15:31     ` Evgenii Shatokhin
2024-12-02  7:29     ` Evgenii Shatokhin
2024-12-02  7:29       ` Evgenii Shatokhin
2024-12-06 10:02   ` Björn Töpel
2024-12-06 10:02     ` Björn Töpel
2024-12-06 23:35     ` Bagas Sanjaya [this message]
2024-12-06 23:35       ` Bagas Sanjaya
2024-12-09 14:57     ` Robbin Ehn
2024-12-09 14:57       ` Robbin Ehn
2024-11-27 17:29 ` [PATCH v3 4/7] riscv: ftrace: do not use stop_machine to update code Andy Chiu
2024-11-27 17:29   ` Andy Chiu
2024-11-27 17:29 ` [PATCH v3 5/7] riscv: vector: Support calling schedule() for preemptible Vector Andy Chiu
2024-11-27 17:29   ` Andy Chiu
2024-11-27 17:29 ` [PATCH v3 6/7] riscv: add a data fence for CMODX in the kernel mode Andy Chiu
2024-11-27 17:29   ` Andy Chiu
2025-03-10 19:08   ` Björn Töpel
2025-03-10 19:08     ` Björn Töpel
2025-03-11 12:44     ` Andrea Parri
2025-03-11 12:44       ` Andrea Parri
2025-03-11 14:53       ` Björn Töpel
2025-03-11 14:53         ` Björn Töpel
2025-03-11 18:11         ` Andrea Parri
2025-03-11 18:11           ` Andrea Parri
2025-03-13 18:12           ` Andy Chiu
2025-03-13 18:12             ` Andy Chiu
2025-03-14 15:23             ` Andrea Parri
2025-03-14 15:23               ` Andrea Parri
2024-11-27 17:29 ` [PATCH v3 7/7] riscv: ftrace: support PREEMPT Andy Chiu
2024-11-27 17:29   ` Andy Chiu
2025-03-10 19:09   ` Björn Töpel
2025-03-10 19:09     ` Björn Töpel
2024-11-27 21:25 ` [PATCH v3 0/7] riscv: ftrace: atmoic patching and preempt improvements Björn Töpel
2024-11-27 21:25   ` Björn Töpel
2024-12-24  3:15   ` Steven Rostedt
2024-12-24  3:15     ` Steven Rostedt
2024-12-29 19:08     ` Andy Chiu
2024-12-29 19:08       ` Andy Chiu
2025-01-06 15:22       ` Andy Chiu
2025-01-06 15:22         ` Andy Chiu
2024-12-02  7:58 ` Evgenii Shatokhin
2024-12-02  7:58   ` Evgenii Shatokhin
2024-12-11 15:38   ` Andy Chiu
2024-12-11 15:38     ` Andy Chiu
2024-12-03 12:18 ` Björn Töpel
2024-12-03 12:18   ` Björn Töpel
2024-12-03 15:09   ` Evgenii Shatokhin
2024-12-03 15:09     ` Evgenii Shatokhin
2024-12-06  8:39     ` Björn Töpel
2024-12-06  8:39       ` Björn Töpel
2024-12-11 15:48   ` Andy Chiu
2024-12-11 15:48     ` Andy Chiu

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