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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next prev parent reply other threads:[~2024-12-06 23:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20241127172908.17149-1-andybnac@gmail.com>
2024-11-27 17:29 ` [PATCH v3 1/7] riscv: ftrace: support fastcc in Clang for WITH_ARGS Andy Chiu
2024-12-03 12:05 ` Björn Töpel
2024-12-03 14:44 ` Evgenii Shatokhin
2024-11-27 17:29 ` [PATCH v3 3/7] riscv: ftrace: prepare ftrace for atomic code patching Andy Chiu
2024-12-01 15:31 ` Evgenii Shatokhin
2024-12-02 7:29 ` Evgenii Shatokhin
2024-12-06 10:02 ` Björn Töpel
2024-12-06 23:35 ` Bagas Sanjaya [this message]
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
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