linux-kernel - Re: [PATCH v1 16/22] powerpc/ftrace: Minimise number of #ifdefs

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Message-Id: <1650267933.ewyj9l63lo.naveen@linux.ibm.com>
Date:   Mon, 18 Apr 2022 13:29:06 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Ingo Molnar <mingo@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v1 16/22] powerpc/ftrace: Minimise number of #ifdefs

Christophe Leroy wrote:
> A lot of #ifdefs can be replaced by IS_ENABLED()
> 
> Do so.
> 
> This requires to have kernel_toc_addr() defined at all time
> and PPC_INST_LD_TOC as well.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  arch/powerpc/include/asm/code-patching.h |   2 -
>  arch/powerpc/include/asm/module.h        |   2 -
>  arch/powerpc/include/asm/sections.h      |  24 +--
>  arch/powerpc/kernel/trace/ftrace.c       | 201 ++++++++++++-----------
>  4 files changed, 113 insertions(+), 116 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
> index 4260e89f62b1..071fcbec31c5 100644
> --- a/arch/powerpc/include/asm/code-patching.h
> +++ b/arch/powerpc/include/asm/code-patching.h
> @@ -217,7 +217,6 @@ static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
>  	return addr;
>  }
> 
> -#ifdef CONFIG_PPC64
>  /*
>   * Some instruction encodings commonly used in dynamic ftracing
>   * and function live patching.
> @@ -234,6 +233,5 @@ static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
> 
>  /* usually preceded by a mflr r0 */
>  #define PPC_INST_STD_LR		PPC_RAW_STD(_R0, _R1, PPC_LR_STKOFF)
> -#endif /* CONFIG_PPC64 */
> 
>  #endif /* _ASM_POWERPC_CODE_PATCHING_H */
> diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h
> index e6f5963fd96e..700d7ecd9012 100644
> --- a/arch/powerpc/include/asm/module.h
> +++ b/arch/powerpc/include/asm/module.h
> @@ -41,9 +41,7 @@ struct mod_arch_specific {
> 
>  #ifdef CONFIG_FUNCTION_TRACER
>  	unsigned long tramp;
> -#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
>  	unsigned long tramp_regs;
> -#endif
>  #endif
> 
>  	/* List of BUG addresses, source line numbers and filenames */
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 8be2c491c733..6980eaeb16fe 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -29,18 +29,6 @@ extern char start_virt_trampolines[];
>  extern char end_virt_trampolines[];
>  #endif
> 
> -/*
> - * This assumes the kernel is never compiled -mcmodel=small or
> - * the total .toc is always less than 64k.
> - */
> -static inline unsigned long kernel_toc_addr(void)
> -{
> -	unsigned long toc_ptr;
> -
> -	asm volatile("mr %0, 2" : "=r" (toc_ptr));
> -	return toc_ptr;
> -}
> -
>  static inline int overlaps_interrupt_vector_text(unsigned long start,
>  							unsigned long end)
>  {
> @@ -60,5 +48,17 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
> 
>  #endif
> 
> +/*
> + * This assumes the kernel is never compiled -mcmodel=small or
> + * the total .toc is always less than 64k.
> + */
> +static inline unsigned long kernel_toc_addr(void)
> +{
> +	unsigned long toc_ptr;
> +
> +	asm volatile("mr %0, 2" : "=r" (toc_ptr));
> +	return toc_ptr;
> +}
> +
>  #endif /* __KERNEL__ */
>  #endif	/* _ASM_POWERPC_SECTIONS_H */
> diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
> index ffedf8c82ea8..4dd30e396026 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -150,55 +150,55 @@ __ftrace_make_nop(struct module *mod,
>  		return -EINVAL;
>  	}
> 
> -	/* When using -mkernel_profile or PPC32 there is no load to jump over */
> -	pop = ppc_inst(PPC_RAW_NOP());
> +	if (IS_ENABLED(CONFIG_MPROFILE_KERNEL)) {
> +		/* When using -mkernel_profile or PPC32 there is no load to jump over */
> +		pop = ppc_inst(PPC_RAW_NOP());

Why move this inside the if() statement? You can keep this out and drop 
the else clause.

- Naveen