[PATCH 0/3] Remove unused code after IA-64 removal

[PATCH 0/3] Remove unused code after IA-64 removal

[Heiko Carstens]

While looking into something different I noticed that there are a couple of
Kconfig options which were only selected by IA-64 and which are now unused.

So remove them and simplify the code a bit.

Heiko Carstens (3):
  arch: remove ARCH_THREAD_STACK_ALLOCATOR
  arch: remove ARCH_TASK_STRUCT_ALLOCATOR
  arch: remove ARCH_TASK_STRUCT_ON_STACK

 arch/Kconfig                 | 13 -------------
 arch/powerpc/kexec/core_64.c |  3 +--
 include/linux/init_task.h    |  7 -------
 include/linux/sched.h        |  2 --
 init/init_task.c             | 10 ++--------
 kernel/fork.c                | 26 --------------------------
 6 files changed, 3 insertions(+), 58 deletions(-)

-- 
2.39.2

[PATCH 1/3] arch: remove ARCH_THREAD_STACK_ALLOCATOR

[Heiko Carstens]

IA-64 was the only architecture which selected ARCH_THREAD_STACK_ALLOCATOR.
IA-64 was removed with commit cf8e8658100d ("arch: Remove Itanium (IA-64)
architecture"). Therefore remove support for ARCH_THREAD_STACK_ALLOCATOR as
well.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/Kconfig  |  4 ----
 kernel/fork.c | 20 --------------------
 2 files changed, 24 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index f4b210ab0612..310162b41a1c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -320,10 +320,6 @@ config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 	  should be implemented. Without this, the entire thread_struct
 	  field in task_struct will be left whitelisted.
 
-# Select if arch has its private alloc_thread_stack() function
-config ARCH_THREAD_STACK_ALLOCATOR
-	bool
-
 # Select if arch wants to size task_struct dynamically via arch_task_struct_size:
 config ARCH_WANTS_DYNAMIC_TASK_STRUCT
 	bool
diff --git a/kernel/fork.c b/kernel/fork.c
index 10917c3e1f03..d071809866e0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -179,8 +179,6 @@ static inline void free_task_struct(struct task_struct *tsk)
 }
 #endif
 
-#ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
-
 /*
  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
  * kmemcache based allocator.
@@ -412,24 +410,6 @@ void thread_stack_cache_init(void)
 }
 
 # endif /* THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK) */
-#else /* CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
-
-static int alloc_thread_stack_node(struct task_struct *tsk, int node)
-{
-	unsigned long *stack;
-
-	stack = arch_alloc_thread_stack_node(tsk, node);
-	tsk->stack = stack;
-	return stack ? 0 : -ENOMEM;
-}
-
-static void free_thread_stack(struct task_struct *tsk)
-{
-	arch_free_thread_stack(tsk);
-	tsk->stack = NULL;
-}
-
-#endif /* !CONFIG_ARCH_THREAD_STACK_ALLOCATOR */
 
 /* SLAB cache for signal_struct structures (tsk->signal) */
 static struct kmem_cache *signal_cachep;
-- 
2.39.2

[PATCH 2/3] arch: remove ARCH_TASK_STRUCT_ALLOCATOR

[Heiko Carstens]

IA-64 was the only architecture which selected ARCH_TASK_STRUCT_ALLOCATOR.
IA-64 was removed with commit cf8e8658100d ("arch: Remove Itanium (IA-64)
architecture"). Therefore remove support for ARCH_THREAD_STACK_ALLOCATOR
as well.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/Kconfig  | 5 -----
 kernel/fork.c | 6 ------
 2 files changed, 11 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 310162b41a1c..c2f87ef9f0ae 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -305,13 +305,8 @@ config ARCH_HAS_CPU_FINALIZE_INIT
 config ARCH_TASK_STRUCT_ON_STACK
 	bool
 
-# Select if arch has its private alloc_task_struct() function
-config ARCH_TASK_STRUCT_ALLOCATOR
-	bool
-
 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 	bool
-	depends on !ARCH_TASK_STRUCT_ALLOCATOR
 	help
 	  An architecture should select this to provide hardened usercopy
 	  knowledge about what region of the thread_struct should be
diff --git a/kernel/fork.c b/kernel/fork.c
index d071809866e0..ce8a4b8c04e2 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -165,7 +165,6 @@ void __weak arch_release_task_struct(struct task_struct *tsk)
 {
 }
 
-#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 static struct kmem_cache *task_struct_cachep;
 
 static inline struct task_struct *alloc_task_struct_node(int node)
@@ -177,7 +176,6 @@ static inline void free_task_struct(struct task_struct *tsk)
 {
 	kmem_cache_free(task_struct_cachep, tsk);
 }
-#endif
 
 /*
  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
@@ -1001,7 +999,6 @@ static void set_max_threads(unsigned int max_threads_suggested)
 int arch_task_struct_size __read_mostly;
 #endif
 
-#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
 {
 	/* Fetch thread_struct whitelist for the architecture. */
@@ -1016,12 +1013,10 @@ static void task_struct_whitelist(unsigned long *offset, unsigned long *size)
 	else
 		*offset += offsetof(struct task_struct, thread);
 }
-#endif /* CONFIG_ARCH_TASK_STRUCT_ALLOCATOR */
 
 void __init fork_init(void)
 {
 	int i;
-#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
 #ifndef ARCH_MIN_TASKALIGN
 #define ARCH_MIN_TASKALIGN	0
 #endif
@@ -1034,7 +1029,6 @@ void __init fork_init(void)
 			arch_task_struct_size, align,
 			SLAB_PANIC|SLAB_ACCOUNT,
 			useroffset, usersize, NULL);
-#endif
 
 	/* do the arch specific task caches init */
 	arch_task_cache_init();
-- 
2.39.2

[PATCH 3/3] arch: remove ARCH_TASK_STRUCT_ON_STACK

[Heiko Carstens]

IA-64 was the only architecture which selected ARCH_TASK_STRUCT_ON_STACK.
IA-64 was removed with commit cf8e8658100d ("arch: Remove Itanium (IA-64)
architecture"). Therefore remove support for ARCH_TASK_STRUCT_ON_STACK
as well.

Note: this also reveals a potential bug in powerpc code, which makes use of
__init_task_data without selecting ARCH_TASK_STRUCT_ON_STACK which makes
__init_task_data a no-op. This is broken since commit d11ed3ab3166 ("Expand
INIT_TASK() in init/init_task.c and remove") from 2018 and needs to be
addressed separately.

Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/Kconfig                 |  4 ----
 arch/powerpc/kexec/core_64.c |  3 +--
 include/linux/init_task.h    |  7 -------
 include/linux/sched.h        |  2 --
 init/init_task.c             | 10 ++--------
 5 files changed, 3 insertions(+), 23 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index c2f87ef9f0ae..bfcc7c2dc039 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -301,10 +301,6 @@ config ARCH_HAS_DMA_CLEAR_UNCACHED
 config ARCH_HAS_CPU_FINALIZE_INIT
 	bool
 
-# Select if arch init_task must go in the __init_task_data section
-config ARCH_TASK_STRUCT_ON_STACK
-	bool
-
 config HAVE_ARCH_THREAD_STRUCT_WHITELIST
 	bool
 	help
diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c
index 0bee7ca9a77c..762e4d09aacf 100644
--- a/arch/powerpc/kexec/core_64.c
+++ b/arch/powerpc/kexec/core_64.c
@@ -283,8 +283,7 @@ static void kexec_prepare_cpus(void)
  * We could use a smaller stack if we don't care about anything using
  * current, but that audit has not been performed.
  */
-static union thread_union kexec_stack __init_task_data =
-	{ };
+static union thread_union kexec_stack = { };
 
 /*
  * For similar reasons to the stack above, the kexecing CPU needs to be on a
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 40fc5813cf93..bccb3f1f6262 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -37,13 +37,6 @@ extern struct cred init_cred;
 
 #define INIT_TASK_COMM "swapper"
 
-/* Attach to the init_task data structure for proper alignment */
-#ifdef CONFIG_ARCH_TASK_STRUCT_ON_STACK
-#define __init_task_data __section(".data..init_task")
-#else
-#define __init_task_data /**/
-#endif
-
 /* Attach to the thread_info data structure for proper alignment */
 #define __init_thread_info __section(".data..init_thread_info")
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 292c31697248..c2ecb2e06046 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1955,9 +1955,7 @@ extern void ia64_set_curr_task(int cpu, struct task_struct *p);
 void yield(void);
 
 union thread_union {
-#ifndef CONFIG_ARCH_TASK_STRUCT_ON_STACK
 	struct task_struct task;
-#endif
 #ifndef CONFIG_THREAD_INFO_IN_TASK
 	struct thread_info thread_info;
 #endif
diff --git a/init/init_task.c b/init/init_task.c
index 5727d42149c3..6f6485d554df 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -51,8 +51,7 @@ static struct sighand_struct init_sighand = {
 };
 
 #ifdef CONFIG_SHADOW_CALL_STACK
-unsigned long init_shadow_call_stack[SCS_SIZE / sizeof(long)]
-		__init_task_data = {
+unsigned long init_shadow_call_stack[SCS_SIZE / sizeof(long)] = {
 	[(SCS_SIZE / sizeof(long)) - 1] = SCS_END_MAGIC
 };
 #endif
@@ -61,12 +60,7 @@ unsigned long init_shadow_call_stack[SCS_SIZE / sizeof(long)]
  * Set up the first task table, touch at your own risk!. Base=0,
  * limit=0x1fffff (=2MB)
  */
-struct task_struct init_task
-#ifdef CONFIG_ARCH_TASK_STRUCT_ON_STACK
-	__init_task_data
-#endif
-	__aligned(L1_CACHE_BYTES)
-= {
+struct task_struct init_task __aligned(L1_CACHE_BYTES) = {
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 	.thread_info	= INIT_THREAD_INFO(init_task),
 	.stack_refcount	= REFCOUNT_INIT(1),
-- 
2.39.2

Re: [PATCH 0/3] Remove unused code after IA-64 removal

[Ard Biesheuvel]

On Thu, 16 Nov 2023 at 08:37, Heiko Carstens <hca@linux.ibm.com> wrote:
>
> While looking into something different I noticed that there are a couple of
> Kconfig options which were only selected by IA-64 and which are now unused.
>
> So remove them and simplify the code a bit.
>
> Heiko Carstens (3):
>   arch: remove ARCH_THREAD_STACK_ALLOCATOR
>   arch: remove ARCH_TASK_STRUCT_ALLOCATOR
>   arch: remove ARCH_TASK_STRUCT_ON_STACK
>

Acked-by: Ard Biesheuvel <ardb@kernel.org>

>  arch/Kconfig                 | 13 -------------
>  arch/powerpc/kexec/core_64.c |  3 +--
>  include/linux/init_task.h    |  7 -------
>  include/linux/sched.h        |  2 --
>  init/init_task.c             | 10 ++--------
>  kernel/fork.c                | 26 --------------------------
>  6 files changed, 3 insertions(+), 58 deletions(-)
>
> --
> 2.39.2
>

Re: [PATCH 0/3] Remove unused code after IA-64 removal

[Arnd Bergmann]

On Thu, Nov 16, 2023, at 14:36, Heiko Carstens wrote:
> While looking into something different I noticed that there are a couple of
> Kconfig options which were only selected by IA-64 and which are now unused.
>
> So remove them and simplify the code a bit.
>
> Heiko Carstens (3):
>   arch: remove ARCH_THREAD_STACK_ALLOCATOR
>   arch: remove ARCH_TASK_STRUCT_ALLOCATOR
>   arch: remove ARCH_TASK_STRUCT_ON_STACK

Nice cleanup!

Reviewed-by: Arnd Bergmann <arnd@arndb.de>