From: "Björn Töpel" <bjorn@kernel.org>
To: Andy Chiu <andy.chiu@sifive.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alexghiti@rivosinc.com>,
Zong Li <zong.li@sifive.com>,
Steven Rostedt <rostedt@goodmis.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Bill Wendling <morbo@google.com>,
Justin Stitt <justinstitt@google.com>,
Puranjay Mohan <puranjay@kernel.org>
Cc: Palmer Dabbelt <palmer@rivosinc.com>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-trace-kernel@vger.kernel.org, llvm@lists.linux.dev,
Evgenii Shatokhin <e.shatokhin@yadro.com>,
Andy Chiu <andy.chiu@sifive.com>
Subject: Re: [PATCH v2 2/6] riscv: ftrace: align patchable functions to 4 Byte boundary
Date: Tue, 13 Aug 2024 13:11:16 +0200 [thread overview]
Message-ID: <8734n8ad9n.fsf@all.your.base.are.belong.to.us> (raw)
In-Reply-To: <20240628-dev-andyc-dyn-ftrace-v4-v2-2-1e5f4cb1f049@sifive.com>
Andy Chiu <andy.chiu@sifive.com> writes:
> We are changing ftrace code patching in order to remove dependency from
> stop_machine() and enable kernel preemption. This requires us to align
> functions entry at a 4-B align address.
>
> However, -falign-functions on older versions of GCC alone was not strong
> enoungh to align all functions. In fact, cold functions are not aligned
> after turning on optimizations. We consider this is a bug in GCC and
> turn off guess-branch-probility as a workaround to align all functions.
>
> GCC bug id: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88345
>
> The option -fmin-function-alignment is able to align all functions
> properly on newer versions of gcc. So, we add a cc-option to test if
> the toolchain supports it.
>
> Suggested-by: Evgenii Shatokhin <e.shatokhin@yadro.com>
> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
next prev parent reply other threads:[~2024-08-13 11:11 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-28 11:47 [PATCH v2 0/6] riscv: ftrace: atmoic patching and preempt improvements Andy Chiu
2024-06-28 11:47 ` [PATCH v2 1/6] riscv: ftrace: support fastcc in Clang for WITH_ARGS Andy Chiu
2024-08-13 11:09 ` Björn Töpel
2024-08-22 8:39 ` Andy Chiu
2024-06-28 11:47 ` [PATCH v2 2/6] riscv: ftrace: align patchable functions to 4 Byte boundary Andy Chiu
2024-08-13 11:11 ` Björn Töpel [this message]
2024-06-28 11:47 ` [PATCH v2 3/6] riscv: ftrace: prepare ftrace for atomic code patching Andy Chiu
2024-08-13 12:59 ` Björn Töpel
2024-08-14 12:57 ` Björn Töpel
2024-09-11 10:57 ` Andy Chiu
2024-09-11 14:37 ` Björn Töpel
2024-09-11 15:03 ` Tao Chiu
2024-09-11 17:16 ` Björn Töpel
2024-06-28 11:47 ` [PATCH v2 4/6] riscv: ftrace: do not use stop_machine to update code Andy Chiu
2024-06-28 11:47 ` [PATCH v2 5/6] riscv: vector: Support calling schedule() for preemptible Vector Andy Chiu
2024-06-28 11:47 ` [PATCH v2 6/6] riscv: ftrace: support PREEMPT Andy Chiu
2024-08-13 11:00 ` [PATCH v2 0/6] riscv: ftrace: atmoic patching and preempt improvements Björn Töpel
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