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

[Song Liu]

On Fri, Jun 16, 2023 at 1:52 AM Mike Rapoport  wrote:
>
> From: "Mike Rapoport (IBM)" 
>
> 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) 

Acked-by: Song Liu 

> ---
>  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
>

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

[Mike Rapoport]

From: "Mike Rapoport (IBM)" 

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) 
---
 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