Re: [PATCH v2 11/12] x86/ftrace: enable dynamic ftrace without CONFIG_MODULES

Song Liu
2023-06-16T20:19:06Z

On Fri, Jun 16, 2023 at 1:52 AM Mike Rapoport <rppt@kernel.org> wrote:
>
> 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
>