The cache parameter of getcpu() is useless nowadays for various reasons. * It is never passed by userspace for either the vDSO or syscalls. * It is never used by the kernel. * It could not be made to work on the current vDSO architecture. * The structure definition is not part of the UAPI headers. * vdso_getcpu() is superseded by restartable sequences in any case.

Remove the struct and its header.

As a side-effect we get rid of an unwanted inclusion of the linux/ header namespace from vDSO code.

Signed-off-by: Thomas Weißschuh thomas.weissschuh@linutronix.de --- Changes in v3: - Rebase on v6.19-rc1 - Fix conflict with UML vdso_getcpu() removal - Flesh out commit message - Link to v2: https://lore.kernel.org/r/20251013-getcpu_cache-v2-1-880fbfa3b7cc@linutronix...

Changes in v2: - Rebase on v6.18-rc1 - Link to v1: https://lore.kernel.org/r/20250826-getcpu_cache-v1-1-8748318f6141@linutronix... --- 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/vdso/getcpu.c | 3 +-- arch/s390/kernel/vdso/vdso.h | 4 +--- arch/x86/entry/vdso/vgetcpu.c | 5 ++--- arch/x86/include/asm/vdso/processor.h | 4 +--- include/linux/getcpu.h | 19 ------------------- include/linux/syscalls.h | 3 +-- kernel/sys.c | 4 +--- tools/testing/selftests/vDSO/vdso_test_getcpu.c | 4 +--- 9 files changed, 10 insertions(+), 41 deletions(-)

diff --git a/arch/loongarch/vdso/vgetcpu.c b/arch/loongarch/vdso/vgetcpu.c index 73af49242ecd..6f054ec898c7 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) { @@ -28,8 +27,8 @@ 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/vdso/getcpu.c b/arch/s390/kernel/vdso/getcpu.c index 5c5d4a848b76..1e17665616c5 100644 --- a/arch/s390/kernel/vdso/getcpu.c +++ b/arch/s390/kernel/vdso/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/vdso/vdso.h b/arch/s390/kernel/vdso/vdso.h index 8cff033dd854..1fe52a6f5a56 100644 --- a/arch/s390/kernel/vdso/vdso.h +++ b/arch/s390/kernel/vdso/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 e4640306b2e3..6381b472b7c5 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 7000aeb59aa2..93e0e24e5cb4 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/include/linux/getcpu.h b/include/linux/getcpu.h deleted file mode 100644 index c304dcdb4eac..000000000000 --- 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 cf84d98964b2..23704e006afd 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; @@ -718,7 +717,7 @@ 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 8b58eece4e58..f1780ab132a3 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> @@ -2876,8 +2875,7 @@ 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 bea8ad54da11..3fe49cbdae98 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: 8f0b4cce4481fb22653697cced8d0d04027cb1e8 change-id: 20250825-getcpu_cache-3abcd2e65437

Best regards,