From: Oleksandr Natalenko <oleksandr@natalenko.name>
Date: Mon, 8 May 2023 22:21:53 +0200
Subject: [PATCH] mm: expose per-process KSM control via syscalls
d7597f59d1d3 added a new API to enable per-process KSM control. It
however uses prctl, which doesn't allow controlling KSM from outside of
the current process.
Hence, expose this API via 3 syscalls: process_ksm_enable,
process_ksm_disable and process_ksm_status. Given sufficient privileges,
auto-KSM can be enable by another process.
Since these syscalls are not in the upstream kernel, also expose their
numbers under /sys/kernel/process_ksm so that userspace tooling like
uksmd knows how to use them.
Signed-off-by: Oleksandr Natalenko <oleksandr@natalenko.name>
---
arch/alpha/kernel/syscalls/syscall.tbl | 3 +
arch/arm/tools/syscall.tbl | 3 +
arch/arm64/include/asm/unistd.h | 2 +-
arch/arm64/include/asm/unistd32.h | 6 +
arch/ia64/kernel/syscalls/syscall.tbl | 3 +
arch/m68k/kernel/syscalls/syscall.tbl | 3 +
arch/microblaze/kernel/syscalls/syscall.tbl | 3 +
arch/mips/kernel/syscalls/syscall_n32.tbl | 3 +
arch/mips/kernel/syscalls/syscall_n64.tbl | 3 +
arch/mips/kernel/syscalls/syscall_o32.tbl | 3 +
arch/parisc/kernel/syscalls/syscall.tbl | 3 +
arch/powerpc/kernel/syscalls/syscall.tbl | 3 +
arch/s390/kernel/syscalls/syscall.tbl | 3 +
arch/sh/kernel/syscalls/syscall.tbl | 3 +
arch/sparc/kernel/syscalls/syscall.tbl | 3 +
arch/x86/entry/syscalls/syscall_32.tbl | 3 +
arch/x86/entry/syscalls/syscall_64.tbl | 3 +
arch/xtensa/kernel/syscalls/syscall.tbl | 3 +
include/linux/syscalls.h | 3 +
include/uapi/asm-generic/unistd.h | 11 +-
kernel/sys.c | 147 ++++++++++++++++++++
kernel/sys_ni.c | 3 +
22 files changed, 218 insertions(+), 2 deletions(-)
diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl
index ad37569d0..9f4311e21 100644
--- a/arch/alpha/kernel/syscalls/syscall.tbl
+++ b/arch/alpha/kernel/syscalls/syscall.tbl
@@ -492,3 +492,6 @@
560 common set_mempolicy_home_node sys_ni_syscall
561 common cachestat sys_cachestat
562 common fchmodat2 sys_fchmodat2
+563 common process_ksm_enable sys_process_ksm_enable
+564 common process_ksm_disable sys_process_ksm_disable
+565 common process_ksm_status sys_process_ksm_status
diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
index c572d6c3d..8d40b3a45 100644
--- a/arch/arm/tools/syscall.tbl
+++ b/arch/arm/tools/syscall.tbl
@@ -466,3 +466,6 @@
450 common set_mempolicy_home_node sys_set_mempolicy_home_node
451 common cachestat sys_cachestat
452 common fchmodat2 sys_fchmodat2
+453 common process_ksm_enable sys_process_ksm_enable
+454 common process_ksm_disable sys_process_ksm_disable
+455 common process_ksm_status sys_process_ksm_status
diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
index bd77253b6..f33190f17 100644
--- a/arch/arm64/include/asm/unistd.h
+++ b/arch/arm64/include/asm/unistd.h
@@ -39,7 +39,7 @@
#define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5)
#define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800)
-#define __NR_compat_syscalls 453
+#define __NR_compat_syscalls 456
#endif
#define __ARCH_WANT_SYS_CLONE
diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index 78b68311e..8c8b1c749 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -911,6 +911,12 @@ __SYSCALL(__NR_set_mempolicy_home_node, sys_set_mempolicy_home_node)
__SYSCALL(__NR_cachestat, sys_cachestat)
#define __NR_fchmodat2 452
__SYSCALL(__NR_fchmodat2, sys_fchmodat2)
+#define __NR_process_ksm_enable 453
+__SYSCALL(__NR_process_ksm_enable, sys_process_ksm_enable)
+#define __NR_process_ksm_disable 454
+__SYSCALL(__NR_process_ksm_disable, sys_process_ksm_disable)
+#define __NR_process_ksm_status 455
+__SYSCALL(__NR_process_ksm_status, sys_process_ksm_status)
/*
* Please add new compat syscalls above this comment and update
diff --git a/arch/ia64/kernel/syscalls/syscall.tbl b/arch/ia64/kernel/syscalls/syscall.tbl
index 83d8609ae..2c370b569 100644
--- a/arch/ia64/kernel/syscalls/syscall.tbl
+++ b/arch/ia64/kernel/syscalls/syscall.tbl
@@ -373,3 +373,6 @@
450 common set_mempolicy_home_node sys_set_mempolicy_home_node
451 common cachestat sys_cachestat
452 common fchmodat2 sys_fchmodat2
+453 common process_ksm_enable sys_process_ksm_enable
+454 common process_ksm_disable sys_process_ksm_disable
+455 common process_ksm_status sys_process_ksm_status
diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl
index 259ceb125..346033761 100644
--- a/arch/m68k/kernel/syscalls/syscall.tbl
+++ b/arch/m68k/kernel/syscalls/syscall.tbl
@@ -452,3 +452,6 @@
450 common set_mempolicy_home_node sys_set_mempolicy_home_node
451 common cachestat sys_cachestat
452 common fchmodat2 sys_fchmodat2
+453 common process_ksm_enable sys_process_ksm_enable
+454 common process_ksm_disable sys_process_ksm_disable
+455 common process_ksm_status sys_process_ksm_status
diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl
index a3798c263..3d550ff34 100644
--- a/arch/microblaze/kernel/syscalls/syscall.tbl
+++ b/arch/microblaze/kernel/syscalls/syscall.tbl
@@ -458,3 +458,6 @@
450 common set_mempolicy_home_node sys_set_mempolicy_home_node
451 common cachestat sys_cachestat
452 common fchmodat2 sys_fchmodat2
+453 common process_ksm_enable sys_process_ksm_enable
+454 common process_ksm_disable sys_process_ksm_disable
+455 common process_ksm_status sys_process_ksm_status
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index 152034b8e..49bedc66c 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -391,3 +391,6 @@
450 n32 set_mempolicy_home_node sys_set_mempolicy_home_node
451 n32 cachestat sys_cachestat
452 n32 fchmodat2 sys_fchmodat2
+453 n32 process_ksm_enable sys_process_ksm_enable
+454 n32 process_ksm_disable sys_process_ksm_disable
+455 n32 process_ksm_status sys_process_ksm_status
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index cb5e757f6..5c17a0a34 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -367,3 +367,6 @@
450 common set_mempolicy_home_node sys_set_mempolicy_home_node
451 n64 cachestat sys_cachestat
452 n64 fchmodat2 sys_fchmodat2
+453 n64 process_ksm_enable sys_process_ksm_enable
+454 n64 process_ksm_disable sys_process_ksm_disable
+455 n64 process_ksm_status sys_process_ksm_status
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 1a646813a..95dbd2c60 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -440,3 +440,6 @@
450 o32 set_mempolicy_home_node sys_set_mempolicy_home_node
451 o32 cachestat sys_cachestat
452 o32 fchmodat2 sys_fchmodat2
+453 o32 process_ksm_enable sys_process_ksm_enable
+454 o32 process_ksm_disable sys_process_ksm_disable
+455 o32 process_ksm_status sys_process_ksm_status
diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
index e97c175b5..9b325ef36 100644
--- a/arch/parisc/kernel/syscalls/syscall.tbl
+++ b/arch/parisc/kernel/syscalls/syscall.tbl
@@ -451,3 +451,6 @@
450 common set_mempolicy_home_node sys_set_mempolicy_home_node
451 common cachestat sys_cachestat
452 common fchmodat2 sys_fchmodat2
+453 common process_ksm_enable sys_process_ksm_enable
+454 common process_ksm_disable sys_process_ksm_disable
+455 common process_ksm_status sys_process_ksm_status
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 20e50586e..b62ba0834 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -539,3 +539,6 @@
450 nospu set_mempolicy_home_node sys_set_mempolicy_home_node
451 common cachestat sys_cachestat
452 common fchmodat2 sys_fchmodat2
+453 common process_ksm_enable sys_process_ksm_enable
+454 common process_ksm_disable sys_process_ksm_disable
+455 common process_ksm_status sys_process_ksm_status
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index 0122cc156..70165723f 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -455,3 +455,6 @@
450 common set_mempolicy_home_node sys_set_mempolicy_home_node sys_set_mempolicy_home_node
451 common cachestat sys_cachestat sys_cachestat
452 common fchmodat2 sys_fchmodat2 sys_fchmodat2
+453 common process_ksm_enable sys_process_ksm_enable sys_process_ksm_enable
+454 common process_ksm_disable sys_process_ksm_disable sys_process_ksm_disable
+455 common process_ksm_status sys_process_ksm_status sys_process_ksm_status
diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl
index e90d585c4..80769b880 100644
--- a/arch/sh/kernel/syscalls/syscall.tbl
+++ b/arch/sh/kernel/syscalls/syscall.tbl
@@ -455,3 +455,6 @@
450 common set_mempolicy_home_node sys_set_mempolicy_home_node
451 common cachestat sys_cachestat
452 common fchmodat2 sys_fchmodat2
+453 common process_ksm_enable sys_process_ksm_enable
+454 common process_ksm_disable sys_process_ksm_disable
+455 common process_ksm_status sys_process_ksm_status
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index 4ed06c71c..fb3514cce 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -498,3 +498,6 @@
450 common set_mempolicy_home_node sys_set_mempolicy_home_node
451 common cachestat sys_cachestat
452 common fchmodat2 sys_fchmodat2
+453 common process_ksm_enable sys_process_ksm_enable
+454 common process_ksm_disable sys_process_ksm_disable
+455 common process_ksm_status sys_process_ksm_status
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 2d0b1bd86..80a57f6a8 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -457,3 +457,6 @@
450 i386 set_mempolicy_home_node sys_set_mempolicy_home_node
451 i386 cachestat sys_cachestat
452 i386 fchmodat2 sys_fchmodat2
+453 i386 process_ksm_enable sys_process_ksm_enable
+454 i386 process_ksm_disable sys_process_ksm_disable
+455 i386 process_ksm_status sys_process_ksm_status
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 1d6eee30e..38faca76e 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -375,6 +375,9 @@
451 common cachestat sys_cachestat
452 common fchmodat2 sys_fchmodat2
453 64 map_shadow_stack sys_map_shadow_stack
+454 common process_ksm_enable sys_process_ksm_enable
+455 common process_ksm_disable sys_process_ksm_disable
+456 common process_ksm_status sys_process_ksm_status
#
# Due to a historical design error, certain syscalls are numbered differently
diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl
index fc1a4f3c8..83f5032b2 100644
--- a/arch/xtensa/kernel/syscalls/syscall.tbl
+++ b/arch/xtensa/kernel/syscalls/syscall.tbl
@@ -423,3 +423,6 @@
450 common set_mempolicy_home_node sys_set_mempolicy_home_node
451 common cachestat sys_cachestat
452 common fchmodat2 sys_fchmodat2
+453 common process_ksm_enable sys_process_ksm_enable
+454 common process_ksm_disable sys_process_ksm_disable
+455 common process_ksm_status sys_process_ksm_status
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 22bc6bc14..da013ad43 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -799,6 +799,9 @@ asmlinkage long sys_madvise(unsigned long start, size_t len, int behavior);
asmlinkage long sys_process_madvise(int pidfd, const struct iovec __user *vec,
size_t vlen, int behavior, unsigned int flags);
asmlinkage long sys_process_mrelease(int pidfd, unsigned int flags);
+asmlinkage long sys_process_ksm_enable(int pidfd, unsigned int flags);
+asmlinkage long sys_process_ksm_disable(int pidfd, unsigned int flags);
+asmlinkage long sys_process_ksm_status(int pidfd, unsigned int flags);
asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
unsigned long prot, unsigned long pgoff,
unsigned long flags);
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index abe087c53..e393422e2 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -823,8 +823,17 @@ __SYSCALL(__NR_cachestat, sys_cachestat)
#define __NR_fchmodat2 452
__SYSCALL(__NR_fchmodat2, sys_fchmodat2)
+#define __NR_process_ksm_enable 453
+__SYSCALL(__NR_process_ksm_enable, sys_process_ksm_enable)
+
+#define __NR_process_ksm_disable 454
+__SYSCALL(__NR_process_ksm_disable, sys_process_ksm_disable)
+
+#define __NR_process_ksm_status 455
+__SYSCALL(__NR_process_ksm_status, sys_process_ksm_status)
+
#undef __NR_syscalls
-#define __NR_syscalls 453
+#define __NR_syscalls 456
/*
* 32 bit systems traditionally used different
diff --git a/kernel/sys.c b/kernel/sys.c
index 2410e3999..b0841a2dd 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2727,6 +2727,153 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
return error;
}
+#ifdef CONFIG_KSM
+enum pkc_action {
+ PKSM_ENABLE = 0,
+ PKSM_DISABLE,
+ PKSM_STATUS,
+};
+
+static long do_process_ksm_control(int pidfd, enum pkc_action action)
+{
+ long ret;
+ struct pid *pid;
+ struct task_struct *task;
+ struct mm_struct *mm;
+ unsigned int f_flags;
+
+ pid = pidfd_get_pid(pidfd, &f_flags);
+ if (IS_ERR(pid)) {
+ ret = PTR_ERR(pid);
+ goto out;
+ }
+
+ task = get_pid_task(pid, PIDTYPE_PID);
+ if (!task) {
+ ret = -ESRCH;
+ goto put_pid;
+ }
+
+ /* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */
+ mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
+ if (IS_ERR_OR_NULL(mm)) {
+ ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
+ goto release_task;
+ }
+
+ /* Require CAP_SYS_NICE for influencing process performance. */
+ if (!capable(CAP_SYS_NICE)) {
+ ret = -EPERM;
+ goto release_mm;
+ }
+
+ if (mmap_write_lock_killable(mm)) {
+ ret = -EINTR;
+ goto release_mm;
+ }
+
+ switch (action) {
+ case PKSM_ENABLE:
+ ret = ksm_enable_merge_any(mm);
+ break;
+ case PKSM_DISABLE:
+ ret = ksm_disable_merge_any(mm);
+ break;
+ case PKSM_STATUS:
+ ret = !!test_bit(MMF_VM_MERGE_ANY, &mm->flags);
+ break;
+ }
+
+ mmap_write_unlock(mm);
+
+release_mm:
+ mmput(mm);
+release_task:
+ put_task_struct(task);
+put_pid:
+ put_pid(pid);
+out:
+ return ret;
+}
+#endif /* CONFIG_KSM */
+
+SYSCALL_DEFINE2(process_ksm_enable, int, pidfd, unsigned int, flags)
+{
+#ifdef CONFIG_KSM
+ if (flags != 0)
+ return -EINVAL;
+
+ return do_process_ksm_control(pidfd, PKSM_ENABLE);
+#else /* CONFIG_KSM */
+ return -ENOSYS;
+#endif /* CONFIG_KSM */
+}
+
+SYSCALL_DEFINE2(process_ksm_disable, int, pidfd, unsigned int, flags)
+{
+#ifdef CONFIG_KSM
+ if (flags != 0)
+ return -EINVAL;
+
+ return do_process_ksm_control(pidfd, PKSM_DISABLE);
+#else /* CONFIG_KSM */
+ return -ENOSYS;
+#endif /* CONFIG_KSM */
+}
+
+SYSCALL_DEFINE2(process_ksm_status, int, pidfd, unsigned int, flags)
+{
+#ifdef CONFIG_KSM
+ if (flags != 0)
+ return -EINVAL;
+
+ return do_process_ksm_control(pidfd, PKSM_STATUS);
+#else /* CONFIG_KSM */
+ return -ENOSYS;
+#endif /* CONFIG_KSM */
+}
+
+#ifdef CONFIG_KSM
+static ssize_t process_ksm_enable_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%u\n", __NR_process_ksm_enable);
+}
+static struct kobj_attribute process_ksm_enable_attr = __ATTR_RO(process_ksm_enable);
+
+static ssize_t process_ksm_disable_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%u\n", __NR_process_ksm_disable);
+}
+static struct kobj_attribute process_ksm_disable_attr = __ATTR_RO(process_ksm_disable);
+
+static ssize_t process_ksm_status_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%u\n", __NR_process_ksm_status);
+}
+static struct kobj_attribute process_ksm_status_attr = __ATTR_RO(process_ksm_status);
+
+static struct attribute *process_ksm_sysfs_attrs[] = {
+ &process_ksm_enable_attr.attr,
+ &process_ksm_disable_attr.attr,
+ &process_ksm_status_attr.attr,
+ NULL,
+};
+
+static const struct attribute_group process_ksm_sysfs_attr_group = {
+ .attrs = process_ksm_sysfs_attrs,
+ .name = "process_ksm",
+};
+
+static int __init process_ksm_sysfs_init(void)
+{
+ return sysfs_create_group(kernel_kobj, &process_ksm_sysfs_attr_group);
+}
+subsys_initcall(process_ksm_sysfs_init);
+#endif /* CONFIG_KSM */
+
SYSCALL_DEFINE3(getcpu, unsigned __user *, cpup, unsigned __user *, nodep,
struct getcpu_cache __user *, unused)
{
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index e137c1385..2d9772d11 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -184,6 +184,9 @@ COND_SYSCALL(mincore);
COND_SYSCALL(madvise);
COND_SYSCALL(process_madvise);
COND_SYSCALL(process_mrelease);
+COND_SYSCALL(process_ksm_enable);
+COND_SYSCALL(process_ksm_disable);
+COND_SYSCALL(process_ksm_status);
COND_SYSCALL(remap_file_pages);
COND_SYSCALL(mbind);
COND_SYSCALL(get_mempolicy);
