Received-SPF: pass (google.com: domain of linux-kernel+bounces-214068-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Date: Thu, 13 Jun 2024 15:36:15 -0700
From: Nathan Chancellor <nathan@kernel.org>
To: Andy Chiu <andy.chiu@sifive.com>
Cc: 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>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	Puranjay Mohan <puranjay@kernel.org>,
	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>
Subject: Re: [PATCH 3/8] riscv: ftrace: support fastcc in Clang for WITH_ARGS
Message-ID: <20240613223615.GA2739249@thelio-3990X>
References: <20240613-dev-andyc-dyn-ftrace-v4-v1-0-1a538e12c01e@sifive.com>
 <20240613-dev-andyc-dyn-ftrace-v4-v1-3-1a538e12c01e@sifive.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240613-dev-andyc-dyn-ftrace-v4-v1-3-1a538e12c01e@sifive.com>

On Thu, Jun 13, 2024 at 03:11:08PM +0800, Andy Chiu wrote:
> Some caller-saved registers which are not defined as function arguments
> in the ABI can still be passed as arguments when the kernel is compiled
> with Clang. As a result, we must save and restore those registers to
> prevent ftrace from clobbering them.
> 
> - [1]: https://reviews.llvm.org/D68559
> Reported-by: Evgenii Shatokhin <e.shatokhin@yadro.com>
> Closes: https://lore.kernel.org/linux-riscv/7e7c7914-445d-426d-89a0-59a9199c45b1@yadro.com/
> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>

Acked-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  arch/riscv/include/asm/ftrace.h |  7 +++++++
>  arch/riscv/kernel/asm-offsets.c |  7 +++++++
>  arch/riscv/kernel/mcount-dyn.S  | 16 ++++++++++++++--
>  3 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
> index 9eb31a7ea0aa..5f81c53dbfd9 100644
> --- a/arch/riscv/include/asm/ftrace.h
> +++ b/arch/riscv/include/asm/ftrace.h
> @@ -144,6 +144,13 @@ struct ftrace_regs {
>  			unsigned long a5;
>  			unsigned long a6;
>  			unsigned long a7;
> +#ifdef CONFIG_CC_IS_CLANG
> +			unsigned long t2;
> +			unsigned long t3;
> +			unsigned long t4;
> +			unsigned long t5;
> +			unsigned long t6;
> +#endif
>  		};
>  	};
>  };
> diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
> index b09ca5f944f7..db5a26fcc9ae 100644
> --- a/arch/riscv/kernel/asm-offsets.c
> +++ b/arch/riscv/kernel/asm-offsets.c
> @@ -497,6 +497,13 @@ void asm_offsets(void)
>  	DEFINE(FREGS_SP,	    offsetof(struct ftrace_regs, sp));
>  	DEFINE(FREGS_S0,	    offsetof(struct ftrace_regs, s0));
>  	DEFINE(FREGS_T1,	    offsetof(struct ftrace_regs, t1));
> +#ifdef CONFIG_CC_IS_CLANG
> +	DEFINE(FREGS_T2,	    offsetof(struct ftrace_regs, t2));
> +	DEFINE(FREGS_T3,	    offsetof(struct ftrace_regs, t3));
> +	DEFINE(FREGS_T4,	    offsetof(struct ftrace_regs, t4));
> +	DEFINE(FREGS_T5,	    offsetof(struct ftrace_regs, t5));
> +	DEFINE(FREGS_T6,	    offsetof(struct ftrace_regs, t6));
> +#endif
>  	DEFINE(FREGS_A0,	    offsetof(struct ftrace_regs, a0));
>  	DEFINE(FREGS_A1,	    offsetof(struct ftrace_regs, a1));
>  	DEFINE(FREGS_A2,	    offsetof(struct ftrace_regs, a2));
> diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
> index 745dd4c4a69c..e988bd26b28b 100644
> --- a/arch/riscv/kernel/mcount-dyn.S
> +++ b/arch/riscv/kernel/mcount-dyn.S
> @@ -96,7 +96,13 @@
>  	REG_S	x8,  FREGS_S0(sp)
>  #endif
>  	REG_S	x6,  FREGS_T1(sp)
> -
> +#ifdef CONFIG_CC_IS_CLANG
> +	REG_S	x7,  FREGS_T2(sp)
> +	REG_S	x28, FREGS_T3(sp)
> +	REG_S	x29, FREGS_T4(sp)
> +	REG_S	x30, FREGS_T5(sp)
> +	REG_S	x31, FREGS_T6(sp)
> +#endif
>  	// save the arguments
>  	REG_S	x10, FREGS_A0(sp)
>  	REG_S	x11, FREGS_A1(sp)
> @@ -115,7 +121,13 @@
>  	REG_L	x8, FREGS_S0(sp)
>  #endif
>  	REG_L	x6,  FREGS_T1(sp)
> -
> +#ifdef CONFIG_CC_IS_CLANG
> +	REG_L	x7,  FREGS_T2(sp)
> +	REG_L	x28, FREGS_T3(sp)
> +	REG_L	x29, FREGS_T4(sp)
> +	REG_L	x30, FREGS_T5(sp)
> +	REG_L	x31, FREGS_T6(sp)
> +#endif
>  	// restore the arguments
>  	REG_L	x10, FREGS_A0(sp)
>  	REG_L	x11, FREGS_A1(sp)
> 
> -- 
> 2.43.0
>