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From:   Song Liu <song@kernel.org>
Date:   Fri, 16 Jun 2023 13:18:48 -0700
Message-ID: <CAPhsuW5N3RuBijpyXrzVk_mpAyUQ5TeTuS2jic6Y-ybFVJpBjg@mail.gmail.com>
Subject: Re: [PATCH v2 11/12] x86/ftrace: enable dynamic ftrace without CONFIG_MODULES
To:     Mike Rapoport <rppt@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
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        Helge Deller <deller@gmx.de>,
        Huacai Chen <chenhuacai@kernel.org>,
        Kent Overstreet <kent.overstreet@linux.dev>,
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        Nadav Amit <nadav.amit@gmail.com>,
        "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
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On Fri, Jun 16, 2023 at 1:52=E2=80=AFAM Mike Rapoport <rppt@kernel.org> wro=
te:
>
> From: "Mike Rapoport (IBM)" <rppt@kernel.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@kernel.org>

Acked-by: Song Liu <song@kernel.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
>