netdev - Re: [PATCH v2 11/12] x86/ftrace: enable dynamic ftrace without CONFIG

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Date: Fri, 16 Jun 2023 13:18:48 -0700
From: Song Liu <song@...nel.org>
To: Mike Rapoport <rppt@...nel.org>
Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, 
	Catalin Marinas <catalin.marinas@....com>, Christophe Leroy <christophe.leroy@...roup.eu>, 
	"David S. Miller" <davem@...emloft.net>, Dinh Nguyen <dinguyen@...nel.org>, 
	Heiko Carstens <hca@...ux.ibm.com>, Helge Deller <deller@....de>, Huacai Chen <chenhuacai@...nel.org>, 
	Kent Overstreet <kent.overstreet@...ux.dev>, Luis Chamberlain <mcgrof@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Michael Ellerman <mpe@...erman.id.au>, 
	Nadav Amit <nadav.amit@...il.com>, "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Puranjay Mohan <puranjay12@...il.com>, 
	Rick Edgecombe <rick.p.edgecombe@...el.com>, Russell King <linux@...linux.org.uk>, 
	Steven Rostedt <rostedt@...dmis.org>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
	Thomas Gleixner <tglx@...utronix.de>, Will Deacon <will@...nel.org>, bpf@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org, 
	linux-mm@...ck.org, linux-modules@...r.kernel.org, 
	linux-parisc@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	linux-s390@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, loongarch@...ts.linux.dev, 
	netdev@...r.kernel.org, sparclinux@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v2 11/12] x86/ftrace: enable dynamic ftrace without CONFIG_MODULES

On Fri, Jun 16, 2023 at 1:52 AM Mike Rapoport <rppt@...nel.org> wrote:
>
> From: "Mike Rapoport (IBM)" <rppt@...nel.org>
>
> Dynamic ftrace must allocate memory for code and this was impossible
> without CONFIG_MODULES.
>
> With execmem separated from the modules code, execmem_text_alloc() is
> available regardless of CONFIG_MODULES.
>
> Remove dependency of dynamic ftrace on CONFIG_MODULES and make
> CONFIG_DYNAMIC_FTRACE select CONFIG_EXECMEM in Kconfig.
>
> Signed-off-by: Mike Rapoport (IBM) <rppt@...nel.org>

Acked-by: Song Liu <song@...nel.org>

> ---
>  arch/x86/Kconfig         |  1 +
>  arch/x86/kernel/ftrace.c | 10 ----------
>  2 files changed, 1 insertion(+), 10 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 53bab123a8ee..ab64bbef9e50 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -35,6 +35,7 @@ config X86_64
>         select SWIOTLB
>         select ARCH_HAS_ELFCORE_COMPAT
>         select ZONE_DMA32
> +       select EXECMEM if DYNAMIC_FTRACE
>
>  config FORCE_DYNAMIC_FTRACE
>         def_bool y
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index f77c63bb3203..a824a5d3b129 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -261,8 +261,6 @@ void arch_ftrace_update_code(int command)
>  /* Currently only x86_64 supports dynamic trampolines */
>  #ifdef CONFIG_X86_64
>
> -#ifdef CONFIG_MODULES
> -/* Module allocation simplifies allocating memory for code */
>  static inline void *alloc_tramp(unsigned long size)
>  {
>         return execmem_text_alloc(size);
> @@ -271,14 +269,6 @@ static inline void tramp_free(void *tramp)
>  {
>         execmem_free(tramp);
>  }
> -#else
> -/* Trampolines can only be created if modules are supported */
> -static inline void *alloc_tramp(unsigned long size)
> -{
> -       return NULL;
> -}
> -static inline void tramp_free(void *tramp) { }
> -#endif
>
>  /* Defined as markers to the end of the ftrace default trampolines */
>  extern void ftrace_regs_caller_end(void);
> --
> 2.35.1
>