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* [PATCH] vdso: Remove struct getcpu_cache
@ 2025-08-26  5:29 Thomas Weißschuh
  0 siblings, 0 replies; only message in thread
From: Thomas Weißschuh @ 2025-08-26  5:29 UTC (permalink / raw)
  To: Huacai Chen, WANG Xuerui, Heiko Carstens, Vasily Gorbik,
	Alexander Gordeev, Christian Borntraeger, Sven Schnelle,
	Andy Lutomirski, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
	Dave Hansen, x86, H. Peter Anvin, Richard Weinberger,
	Anton Ivanov, Johannes Berg, Vincenzo Frascino, Shuah Khan
  Cc: loongarch, linux-kernel, linux-s390, linux-um, linux-api,
	linux-kselftest, Thomas Weißschuh

The cache parameter of getcpu() is not used by the kernel and no user ever
passes it in anyways.

Remove the struct and its header.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
We could also completely remove the parameter, but I am not sure if
that is a good idea for syscalls and vDSO entrypoints.
---
 arch/loongarch/vdso/vgetcpu.c                   |  5 ++---
 arch/s390/kernel/vdso64/getcpu.c                |  3 +--
 arch/s390/kernel/vdso64/vdso.h                  |  4 +---
 arch/x86/entry/vdso/vgetcpu.c                   |  5 ++---
 arch/x86/include/asm/vdso/processor.h           |  4 +---
 arch/x86/um/vdso/um_vdso.c                      |  7 +++----
 include/linux/getcpu.h                          | 19 -------------------
 include/linux/syscalls.h                        |  3 +--
 kernel/sys.c                                    |  4 +---
 tools/testing/selftests/vDSO/vdso_test_getcpu.c |  4 +---
 10 files changed, 13 insertions(+), 45 deletions(-)

diff --git a/arch/loongarch/vdso/vgetcpu.c b/arch/loongarch/vdso/vgetcpu.c
index 5301cd9d0f839eb0fd7b73a1d36e80aaa75d5e76..aefba899873ed035d70766a95b0b6fea881e94df 100644
--- a/arch/loongarch/vdso/vgetcpu.c
+++ b/arch/loongarch/vdso/vgetcpu.c
@@ -4,7 +4,6 @@
  */
 
 #include <asm/vdso.h>
-#include <linux/getcpu.h>
 
 static __always_inline int read_cpu_id(void)
 {
@@ -20,8 +19,8 @@ static __always_inline int read_cpu_id(void)
 }
 
 extern
-int __vdso_getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *unused);
-int __vdso_getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *unused)
+int __vdso_getcpu(unsigned int *cpu, unsigned int *node, void *unused);
+int __vdso_getcpu(unsigned int *cpu, unsigned int *node, void *unused)
 {
 	int cpu_id;
 
diff --git a/arch/s390/kernel/vdso64/getcpu.c b/arch/s390/kernel/vdso64/getcpu.c
index 5c5d4a848b7669436e73df8e3b711e5b876eb3db..1e17665616c5fa766ca66c8de276b212528934bd 100644
--- a/arch/s390/kernel/vdso64/getcpu.c
+++ b/arch/s390/kernel/vdso64/getcpu.c
@@ -2,11 +2,10 @@
 /* Copyright IBM Corp. 2020 */
 
 #include <linux/compiler.h>
-#include <linux/getcpu.h>
 #include <asm/timex.h>
 #include "vdso.h"
 
-int __s390_vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
+int __s390_vdso_getcpu(unsigned *cpu, unsigned *node, void *unused)
 {
 	union tod_clock clk;
 
diff --git a/arch/s390/kernel/vdso64/vdso.h b/arch/s390/kernel/vdso64/vdso.h
index 9e5397e7b590a23c149ccc6043d0c0b0d5ea8457..cadd307d7a365cabf53f5c8d313be3718625533d 100644
--- a/arch/s390/kernel/vdso64/vdso.h
+++ b/arch/s390/kernel/vdso64/vdso.h
@@ -4,9 +4,7 @@
 
 #include <vdso/datapage.h>
 
-struct getcpu_cache;
-
-int __s390_vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused);
+int __s390_vdso_getcpu(unsigned *cpu, unsigned *node, void *unused);
 int __s390_vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz);
 int __s390_vdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts);
 int __s390_vdso_clock_getres(clockid_t clock, struct __kernel_timespec *ts);
diff --git a/arch/x86/entry/vdso/vgetcpu.c b/arch/x86/entry/vdso/vgetcpu.c
index e4640306b2e3c95d74d73037ab6b09294b8e1d6c..6381b472b7c52487bccf3cbf0664c3d7a0e59699 100644
--- a/arch/x86/entry/vdso/vgetcpu.c
+++ b/arch/x86/entry/vdso/vgetcpu.c
@@ -6,17 +6,16 @@
  */
 
 #include <linux/kernel.h>
-#include <linux/getcpu.h>
 #include <asm/segment.h>
 #include <vdso/processor.h>
 
 notrace long
-__vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
+__vdso_getcpu(unsigned *cpu, unsigned *node, void *unused)
 {
 	vdso_read_cpunode(cpu, node);
 
 	return 0;
 }
 
-long getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
+long getcpu(unsigned *cpu, unsigned *node, void *tcache)
 	__attribute__((weak, alias("__vdso_getcpu")));
diff --git a/arch/x86/include/asm/vdso/processor.h b/arch/x86/include/asm/vdso/processor.h
index 7000aeb59aa287e2119c3d43ab3eaf82befb59c4..93e0e24e5cb47f7b0056c13f2a7f2304ed4a0595 100644
--- a/arch/x86/include/asm/vdso/processor.h
+++ b/arch/x86/include/asm/vdso/processor.h
@@ -18,9 +18,7 @@ static __always_inline void cpu_relax(void)
 	native_pause();
 }
 
-struct getcpu_cache;
-
-notrace long __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused);
+notrace long __vdso_getcpu(unsigned *cpu, unsigned *node, void *unused);
 
 #endif /* __ASSEMBLER__ */
 
diff --git a/arch/x86/um/vdso/um_vdso.c b/arch/x86/um/vdso/um_vdso.c
index cbae2584124fd0ff0f9d240c33fefb8d213c84cd..9aa2c62cce6b7a07bbaf8441014d347162d1950d 100644
--- a/arch/x86/um/vdso/um_vdso.c
+++ b/arch/x86/um/vdso/um_vdso.c
@@ -10,14 +10,13 @@
 #define DISABLE_BRANCH_PROFILING
 
 #include <linux/time.h>
-#include <linux/getcpu.h>
 #include <asm/unistd.h>
 
 /* workaround for -Wmissing-prototypes warnings */
 int __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts);
 int __vdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz);
 __kernel_old_time_t __vdso_time(__kernel_old_time_t *t);
-long __vdso_getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *unused);
+long __vdso_getcpu(unsigned int *cpu, unsigned int *node, void *unused);
 
 int __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
 {
@@ -60,7 +59,7 @@ __kernel_old_time_t __vdso_time(__kernel_old_time_t *t)
 __kernel_old_time_t time(__kernel_old_time_t *t) __attribute__((weak, alias("__vdso_time")));
 
 long
-__vdso_getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *unused)
+__vdso_getcpu(unsigned int *cpu, unsigned int *node, void *unused)
 {
 	/*
 	 * UML does not support SMP, we can cheat here. :)
@@ -74,5 +73,5 @@ __vdso_getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *unused
 	return 0;
 }
 
-long getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *tcache)
+long getcpu(unsigned int *cpu, unsigned int *node, void *tcache)
 	__attribute__((weak, alias("__vdso_getcpu")));
diff --git a/include/linux/getcpu.h b/include/linux/getcpu.h
deleted file mode 100644
index c304dcdb4eac2a9117080e6a14f4e3f28d07fd56..0000000000000000000000000000000000000000
--- a/include/linux/getcpu.h
+++ /dev/null
@@ -1,19 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _LINUX_GETCPU_H
-#define _LINUX_GETCPU_H 1
-
-/* Cache for getcpu() to speed it up. Results might be a short time
-   out of date, but will be faster.
-
-   User programs should not refer to the contents of this structure.
-   I repeat they should not refer to it. If they do they will break
-   in future kernels.
-
-   It is only a private cache for vgetcpu(). It will change in future kernels.
-   The user program must store this information per thread (__thread)
-   If you want 100% accurate information pass NULL instead. */
-struct getcpu_cache {
-	unsigned long blob[128 / sizeof(long)];
-};
-
-#endif
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 77f45e5d44139da36a5dacbf9db7b65261d13398..81822d203eac5d8d91488a18ff7fcdc65670df54 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -59,7 +59,6 @@ struct compat_stat;
 struct old_timeval32;
 struct robust_list_head;
 struct futex_waitv;
-struct getcpu_cache;
 struct old_linux_dirent;
 struct perf_event_attr;
 struct file_handle;
@@ -714,7 +713,7 @@ asmlinkage long sys_getrusage(int who, struct rusage __user *ru);
 asmlinkage long sys_umask(int mask);
 asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
 			unsigned long arg4, unsigned long arg5);
-asmlinkage long sys_getcpu(unsigned __user *cpu, unsigned __user *node, struct getcpu_cache __user *cache);
+asmlinkage long sys_getcpu(unsigned __user *cpu, unsigned __user *node, void __user *cache);
 asmlinkage long sys_gettimeofday(struct __kernel_old_timeval __user *tv,
 				struct timezone __user *tz);
 asmlinkage long sys_settimeofday(struct __kernel_old_timeval __user *tv,
diff --git a/kernel/sys.c b/kernel/sys.c
index 1e28b40053ce206d7d0ed27e8a4fce8b616c3565..a830d78c1e1eb1d6cef31294feeb6a88dc0f83f3 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -31,7 +31,6 @@
 #include <linux/tty.h>
 #include <linux/signal.h>
 #include <linux/cn_proc.h>
-#include <linux/getcpu.h>
 #include <linux/task_io_accounting_ops.h>
 #include <linux/seccomp.h>
 #include <linux/cpu.h>
@@ -2813,8 +2812,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 	return error;
 }
 
-SYSCALL_DEFINE3(getcpu, unsigned __user *, cpup, unsigned __user *, nodep,
-		struct getcpu_cache __user *, unused)
+SYSCALL_DEFINE3(getcpu, unsigned __user *, cpup, unsigned __user *, nodep, void __user *, unused)
 {
 	int err = 0;
 	int cpu = raw_smp_processor_id();
diff --git a/tools/testing/selftests/vDSO/vdso_test_getcpu.c b/tools/testing/selftests/vDSO/vdso_test_getcpu.c
index cdeaed45fb26c61f6314c58fe1b71fa0be3c0108..994ce569dc37c6689b1a3c79156e3dfc8bf27f22 100644
--- a/tools/testing/selftests/vDSO/vdso_test_getcpu.c
+++ b/tools/testing/selftests/vDSO/vdso_test_getcpu.c
@@ -16,9 +16,7 @@
 #include "vdso_config.h"
 #include "vdso_call.h"
 
-struct getcpu_cache;
-typedef long (*getcpu_t)(unsigned int *, unsigned int *,
-			 struct getcpu_cache *);
+typedef long (*getcpu_t)(unsigned int *, unsigned int *, void *);
 
 int main(int argc, char **argv)
 {

---
base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
change-id: 20250825-getcpu_cache-3abcd2e65437

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@linutronix.de>


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