From 79e466fda9e193ce504948db62330e24b8623043 Mon Sep 17 00:00:00 2001 From: Oleksandr Natalenko Date: Mon, 6 Mar 2023 23:03:54 +0100 Subject: [PATCH 1/5] mm/ksm: introduce ksm_madvise_merge() helper Move MADV_MERGEABLE part of ksm_madvise() into a dedicated helper since it will be further used for marking VMAs to be merged forcibly. This does not bring any functional changes. Signed-off-by: Oleksandr Natalenko --- include/linux/ksm.h | 2 ++ mm/ksm.c | 54 +++++++++++++++++++++++++++------------------ 2 files changed, 35 insertions(+), 21 deletions(-) diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 7e232ba59..56f2b473e 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -16,6 +16,8 @@ #include #ifdef CONFIG_KSM +int ksm_madvise_merge(struct mm_struct *mm, struct vm_area_struct *vma, + const vm_flags_t *vm_flags); int ksm_madvise(struct vm_area_struct *vma, unsigned long start, unsigned long end, int advice, unsigned long *vm_flags); int __ksm_enter(struct mm_struct *mm); diff --git a/mm/ksm.c b/mm/ksm.c index 2b8d30068..caea387e8 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2471,39 +2471,51 @@ static int ksm_scan_thread(void *nothing) return 0; } -int ksm_madvise(struct vm_area_struct *vma, unsigned long start, - unsigned long end, int advice, unsigned long *vm_flags) +int ksm_madvise_merge(struct mm_struct *mm, struct vm_area_struct *vma, + const vm_flags_t *vm_flags) { - struct mm_struct *mm = vma->vm_mm; int err; - switch (advice) { - case MADV_MERGEABLE: - /* - * Be somewhat over-protective for now! - */ - if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | - VM_PFNMAP | VM_IO | VM_DONTEXPAND | - VM_HUGETLB | VM_MIXEDMAP)) - return 0; /* just ignore the advice */ + /* + * Be somewhat over-protective for now! + */ + if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE | + VM_PFNMAP | VM_IO | VM_DONTEXPAND | + VM_HUGETLB | VM_MIXEDMAP)) + return 0; /* just ignore the advice */ - if (vma_is_dax(vma)) - return 0; + if (vma_is_dax(vma)) + return 0; #ifdef VM_SAO if (*vm_flags & VM_SAO) return 0; #endif #ifdef VM_SPARC_ADI - if (*vm_flags & VM_SPARC_ADI) - return 0; + if (*vm_flags & VM_SPARC_ADI) + return 0; #endif - if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { - err = __ksm_enter(mm); - if (err) - return err; - } + if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) { + err = __ksm_enter(mm); + if (err) + return err; + } + + return 0; +} + +int ksm_madvise(struct vm_area_struct *vma, unsigned long start, + unsigned long end, int advice, unsigned long *vm_flags) +{ + struct mm_struct *mm = vma->vm_mm; + int err; + + switch (advice) { + case MADV_MERGEABLE: + err = ksm_madvise_merge(mm, vma, vm_flags); + if (err) + return err; *vm_flags |= VM_MERGEABLE; break; -- 2.40.0.71.g950264636c From 60ff7efacc021dbbbc0aeeaedc4474b6bf4fde95 Mon Sep 17 00:00:00 2001 From: Oleksandr Natalenko Date: Mon, 6 Mar 2023 23:06:02 +0100 Subject: [PATCH 2/5] mm/ksm: introduce ksm_madvise_unmerge() helper Move MADV_UNMERGEABLE part of ksm_madvise() into a dedicated helper since it will be further used for unmerging VMAs forcibly. This does not bring any functional changes. Signed-off-by: Oleksandr Natalenko --- include/linux/ksm.h | 2 ++ mm/ksm.c | 28 ++++++++++++++++++++-------- 2 files changed, 22 insertions(+), 8 deletions(-) diff --git a/include/linux/ksm.h b/include/linux/ksm.h index 56f2b473e..57ed92987 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -18,6 +18,8 @@ #ifdef CONFIG_KSM int ksm_madvise_merge(struct mm_struct *mm, struct vm_area_struct *vma, const vm_flags_t *vm_flags); +int ksm_madvise_unmerge(struct vm_area_struct *vma, unsigned long start, + unsigned long end, const vm_flags_t *vm_flags); int ksm_madvise(struct vm_area_struct *vma, unsigned long start, unsigned long end, int advice, unsigned long *vm_flags); int __ksm_enter(struct mm_struct *mm); diff --git a/mm/ksm.c b/mm/ksm.c index caea387e8..ab9a15787 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2505,6 +2505,23 @@ int ksm_madvise_merge(struct mm_struct *mm, struct vm_area_struct *vma, return 0; } +int ksm_madvise_unmerge(struct vm_area_struct *vma, unsigned long start, + unsigned long end, const vm_flags_t *vm_flags) +{ + int err; + + if (!(*vm_flags & VM_MERGEABLE)) + return 0; /* just ignore the advice */ + + if (vma->anon_vma) { + err = unmerge_ksm_pages(vma, start, end); + if (err) + return err; + } + + return 0; +} + int ksm_madvise(struct vm_area_struct *vma, unsigned long start, unsigned long end, int advice, unsigned long *vm_flags) { @@ -2521,14 +2538,9 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start, break; case MADV_UNMERGEABLE: - if (!(*vm_flags & VM_MERGEABLE)) - return 0; /* just ignore the advice */ - - if (vma->anon_vma) { - err = unmerge_ksm_pages(vma, start, end); - if (err) - return err; - } + err = ksm_madvise_unmerge(vma, start, end, vm_flags); + if (err) + return err; *vm_flags &= ~VM_MERGEABLE; break; -- 2.40.0.71.g950264636c From accb82ae6fefa24a0c950028e6fa9525d1a94299 Mon Sep 17 00:00:00 2001 From: Oleksandr Natalenko Date: Mon, 6 Mar 2023 23:08:17 +0100 Subject: [PATCH 3/5] mm: introduce pmadv_ksm system call Yes, I know, this looks like a duplicate of `process_madvise()`. There are two reasons to do this, however: 1. implementing a new syscall is exceptionally easy and takes less code lines than ugly `/proc`-based API, although it imposes slightly more difficult usage onto userspace 2. the code gets actually much closer to be merged with `process_madvise()`, and this is a small step in that direction. So, basically, the `pmadv_ksm()` syscall is a twin of `process_madvise()`, but with two differences: 1. it works with MADV\_(UN)\?MERGEABLE hints only 2. it affects the whole address space of the target task The second difference is likely to disappear in case two syscalls are merged, but that's up to either me or to someone else to re-think how to do it. uksmd is already able to use this syscall. Signed-off-by: Oleksandr Natalenko --- mm/madvise.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) diff --git a/mm/madvise.c b/mm/madvise.c index 340125d08..56c37b573 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1522,3 +1522,95 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec, out: return ret; } + +SYSCALL_DEFINE3(pmadv_ksm, int, pidfd, int, behaviour, unsigned int, flags) +{ +#ifdef CONFIG_KSM + ssize_t ret; + struct pid *pid; + struct task_struct *task; + struct mm_struct *mm; + unsigned int f_flags; + struct vm_area_struct *vma; + struct vma_iterator vmi; + + if (flags != 0) { + ret = -EINVAL; + goto out; + } + + switch (behaviour) { + case MADV_MERGEABLE: + case MADV_UNMERGEABLE: + break; + default: + ret = -EINVAL; + goto out; + break; + } + + 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; + } + + vma_iter_init(&vmi, mm, 0); + for_each_vma(vmi, vma) { + switch (behaviour) { + case MADV_MERGEABLE: + ret = ksm_madvise_merge(vma->vm_mm, vma, &vma->vm_flags); + if (!ret) + vm_flags_set(vma, VM_MERGEABLE); + break; + case MADV_UNMERGEABLE: + ret = ksm_madvise_unmerge(vma, vma->vm_start, vma->vm_end, &vma->vm_flags); + if (!ret) + vm_flags_clear(vma, VM_MERGEABLE); + break; + default: + /* look, ma, no brain */ + break; + } + if (ret) + break; + } + + mmap_write_unlock(mm); + +release_mm: + mmput(mm); +release_task: + put_task_struct(task); +put_pid: + put_pid(pid); +out: + return ret; +#else /* CONFIG_KSM */ + return -ENOSYS; +#endif /* CONFIG_KSM */ +} -- 2.40.0.71.g950264636c From c6c76354509538cedbdf11c4c55cb7049f87cf0d Mon Sep 17 00:00:00 2001 From: Oleksandr Natalenko Date: Mon, 4 Oct 2021 22:58:59 +0200 Subject: [PATCH 4/5] mm: wire up pmadv_ksm system call Present `pmadv_ksm()` syscall for all the arches. Signed-off-by: Oleksandr Natalenko --- arch/alpha/kernel/syscalls/syscall.tbl | 1 + arch/arm/tools/syscall.tbl | 1 + arch/arm64/include/asm/unistd.h | 2 +- arch/arm64/include/asm/unistd32.h | 2 ++ arch/ia64/kernel/syscalls/syscall.tbl | 1 + arch/m68k/kernel/syscalls/syscall.tbl | 1 + arch/microblaze/kernel/syscalls/syscall.tbl | 1 + arch/mips/kernel/syscalls/syscall_n32.tbl | 1 + arch/mips/kernel/syscalls/syscall_n64.tbl | 1 + arch/mips/kernel/syscalls/syscall_o32.tbl | 1 + arch/parisc/kernel/syscalls/syscall.tbl | 1 + arch/powerpc/kernel/syscalls/syscall.tbl | 1 + arch/s390/kernel/syscalls/syscall.tbl | 1 + arch/sh/kernel/syscalls/syscall.tbl | 1 + arch/sparc/kernel/syscalls/syscall.tbl | 1 + arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + arch/xtensa/kernel/syscalls/syscall.tbl | 1 + include/linux/syscalls.h | 1 + include/uapi/asm-generic/unistd.h | 5 ++++- kernel/sys_ni.c | 1 + 21 files changed, 25 insertions(+), 2 deletions(-) diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl index 8ebacf37a..c9d25f85d 100644 --- a/arch/alpha/kernel/syscalls/syscall.tbl +++ b/arch/alpha/kernel/syscalls/syscall.tbl @@ -490,3 +490,4 @@ 558 common process_mrelease sys_process_mrelease 559 common futex_waitv sys_futex_waitv 560 common set_mempolicy_home_node sys_ni_syscall +561 common pmadv_ksm sys_pmadv_ksm diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl index ac964612d..90933eabe 100644 --- a/arch/arm/tools/syscall.tbl +++ b/arch/arm/tools/syscall.tbl @@ -464,3 +464,4 @@ 448 common process_mrelease sys_process_mrelease 449 common futex_waitv sys_futex_waitv 450 common set_mempolicy_home_node sys_set_mempolicy_home_node +451 common pmadv_ksm sys_pmadv_ksm diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h index 037feba03..64a514f90 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 451 +#define __NR_compat_syscalls 452 #endif #define __ARCH_WANT_SYS_CLONE diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h index 604a2053d..91f2bb719 100644 --- a/arch/arm64/include/asm/unistd32.h +++ b/arch/arm64/include/asm/unistd32.h @@ -907,6 +907,8 @@ __SYSCALL(__NR_process_mrelease, sys_process_mrelease) __SYSCALL(__NR_futex_waitv, sys_futex_waitv) #define __NR_set_mempolicy_home_node 450 __SYSCALL(__NR_set_mempolicy_home_node, sys_set_mempolicy_home_node) +#define __NR_pmadv_ksm 451 +__SYSCALL(__NR_pmadv_ksm, sys_pmadv_ksm) /* * 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 72c929d99..0d5b1d14b 100644 --- a/arch/ia64/kernel/syscalls/syscall.tbl +++ b/arch/ia64/kernel/syscalls/syscall.tbl @@ -371,3 +371,4 @@ 448 common process_mrelease sys_process_mrelease 449 common futex_waitv sys_futex_waitv 450 common set_mempolicy_home_node sys_set_mempolicy_home_node +451 common pmadv_ksm sys_pmadv_ksm diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl index b1f3940bc..5ccf92556 100644 --- a/arch/m68k/kernel/syscalls/syscall.tbl +++ b/arch/m68k/kernel/syscalls/syscall.tbl @@ -450,3 +450,4 @@ 448 common process_mrelease sys_process_mrelease 449 common futex_waitv sys_futex_waitv 450 common set_mempolicy_home_node sys_set_mempolicy_home_node +451 common pmadv_ksm sys_pmadv_ksm diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl index 820145e47..6b7620859 100644 --- a/arch/microblaze/kernel/syscalls/syscall.tbl +++ b/arch/microblaze/kernel/syscalls/syscall.tbl @@ -456,3 +456,4 @@ 448 common process_mrelease sys_process_mrelease 449 common futex_waitv sys_futex_waitv 450 common set_mempolicy_home_node sys_set_mempolicy_home_node +451 common pmadv_ksm sys_pmadv_ksm diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl index 253ff994e..e4aeedb17 100644 --- a/arch/mips/kernel/syscalls/syscall_n32.tbl +++ b/arch/mips/kernel/syscalls/syscall_n32.tbl @@ -389,3 +389,4 @@ 448 n32 process_mrelease sys_process_mrelease 449 n32 futex_waitv sys_futex_waitv 450 n32 set_mempolicy_home_node sys_set_mempolicy_home_node +451 n32 pmadv_ksm sys_pmadv_ksm diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl index 3f1886ad9..fe88db51e 100644 --- a/arch/mips/kernel/syscalls/syscall_n64.tbl +++ b/arch/mips/kernel/syscalls/syscall_n64.tbl @@ -365,3 +365,4 @@ 448 n64 process_mrelease sys_process_mrelease 449 n64 futex_waitv sys_futex_waitv 450 common set_mempolicy_home_node sys_set_mempolicy_home_node +451 n64 pmadv_ksm sys_pmadv_ksm diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl index 8f243e35a..674cb940b 100644 --- a/arch/mips/kernel/syscalls/syscall_o32.tbl +++ b/arch/mips/kernel/syscalls/syscall_o32.tbl @@ -438,3 +438,4 @@ 448 o32 process_mrelease sys_process_mrelease 449 o32 futex_waitv sys_futex_waitv 450 o32 set_mempolicy_home_node sys_set_mempolicy_home_node +451 o32 pmadv_ksm sys_pmadv_ksm diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl index 0e42fceb2..5914aa460 100644 --- a/arch/parisc/kernel/syscalls/syscall.tbl +++ b/arch/parisc/kernel/syscalls/syscall.tbl @@ -448,3 +448,4 @@ 448 common process_mrelease sys_process_mrelease 449 common futex_waitv sys_futex_waitv 450 common set_mempolicy_home_node sys_set_mempolicy_home_node +451 common pmadv_ksm sys_pmadv_ksm diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl index a0be12747..347894da4 100644 --- a/arch/powerpc/kernel/syscalls/syscall.tbl +++ b/arch/powerpc/kernel/syscalls/syscall.tbl @@ -537,3 +537,4 @@ 448 common process_mrelease sys_process_mrelease 449 common futex_waitv sys_futex_waitv 450 nospu set_mempolicy_home_node sys_set_mempolicy_home_node +451 common pmadv_ksm sys_pmadv_ksm diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl index 799147658..1cd523748 100644 --- a/arch/s390/kernel/syscalls/syscall.tbl +++ b/arch/s390/kernel/syscalls/syscall.tbl @@ -453,3 +453,4 @@ 448 common process_mrelease sys_process_mrelease sys_process_mrelease 449 common futex_waitv sys_futex_waitv sys_futex_waitv 450 common set_mempolicy_home_node sys_set_mempolicy_home_node sys_set_mempolicy_home_node +451 common pmadv_ksm sys_pmadv_ksm sys_pmadv_ksm diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl index 2de85c977..cfc75fa43 100644 --- a/arch/sh/kernel/syscalls/syscall.tbl +++ b/arch/sh/kernel/syscalls/syscall.tbl @@ -453,3 +453,4 @@ 448 common process_mrelease sys_process_mrelease 449 common futex_waitv sys_futex_waitv 450 common set_mempolicy_home_node sys_set_mempolicy_home_node +451 common pmadv_ksm sys_pmadv_ksm diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl index 4398cc6fb..d2c0a6426 100644 --- a/arch/sparc/kernel/syscalls/syscall.tbl +++ b/arch/sparc/kernel/syscalls/syscall.tbl @@ -496,3 +496,4 @@ 448 common process_mrelease sys_process_mrelease 449 common futex_waitv sys_futex_waitv 450 common set_mempolicy_home_node sys_set_mempolicy_home_node +451 common pmadv_ksm sys_pmadv_ksm diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index 320480a8d..331aaf1a7 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -455,3 +455,4 @@ 448 i386 process_mrelease sys_process_mrelease 449 i386 futex_waitv sys_futex_waitv 450 i386 set_mempolicy_home_node sys_set_mempolicy_home_node +451 i386 pmadv_ksm sys_pmadv_ksm diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index c84d12608..14902db4c 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -372,6 +372,7 @@ 448 common process_mrelease sys_process_mrelease 449 common futex_waitv sys_futex_waitv 450 common set_mempolicy_home_node sys_set_mempolicy_home_node +451 common pmadv_ksm sys_pmadv_ksm # # 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 52c94ab5c..1518e261d 100644 --- a/arch/xtensa/kernel/syscalls/syscall.tbl +++ b/arch/xtensa/kernel/syscalls/syscall.tbl @@ -421,3 +421,4 @@ 448 common process_mrelease sys_process_mrelease 449 common futex_waitv sys_futex_waitv 450 common set_mempolicy_home_node sys_set_mempolicy_home_node +451 common pmadv_ksm sys_pmadv_ksm diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 33a0ee3bc..62f14e800 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -919,6 +919,7 @@ 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_pmadv_ksm(int pidfd, int behavior, 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 45fa180cc..40f7e6d04 100644 --- a/include/uapi/asm-generic/unistd.h +++ b/include/uapi/asm-generic/unistd.h @@ -886,8 +886,11 @@ __SYSCALL(__NR_futex_waitv, sys_futex_waitv) #define __NR_set_mempolicy_home_node 450 __SYSCALL(__NR_set_mempolicy_home_node, sys_set_mempolicy_home_node) +#define __NR_pmadv_ksm 451 +__SYSCALL(__NR_pmadv_ksm, sys_pmadv_ksm) + #undef __NR_syscalls -#define __NR_syscalls 451 +#define __NR_syscalls 452 /* * 32 bit systems traditionally used different diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index 860b2dcf3..810e1fcaf 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -292,6 +292,7 @@ COND_SYSCALL(mincore); COND_SYSCALL(madvise); COND_SYSCALL(process_madvise); COND_SYSCALL(process_mrelease); +COND_SYSCALL(pmadv_ksm); COND_SYSCALL(remap_file_pages); COND_SYSCALL(mbind); COND_SYSCALL(get_mempolicy); -- 2.40.0.71.g950264636c From 6b196dcd75c67d83426f869e6858311d67f3c6ab Mon Sep 17 00:00:00 2001 From: Oleksandr Natalenko Date: Mon, 4 Oct 2021 22:59:38 +0200 Subject: [PATCH 5/5] mm: add sysfs entry for pmadv_ksm syscall number As `pmadv_ksm()` syscall is out-of-tree, maintain a separate `/sys/kernel/pmadv/ksm` file with a syscall number so that userspace tools can always know what to use in runtime even if the syscall number shifts after adding another in-tree syscall. The idea is borrowed from futex2 submission. Signed-off-by: Oleksandr Natalenko --- mm/madvise.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/mm/madvise.c b/mm/madvise.c index 56c37b573..36e756355 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1614,3 +1614,28 @@ SYSCALL_DEFINE3(pmadv_ksm, int, pidfd, int, behaviour, unsigned int, flags) return -ENOSYS; #endif /* CONFIG_KSM */ } + +#ifdef CONFIG_KSM +static ssize_t ksm_show(struct kobject *kobj, struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%u\n", __NR_pmadv_ksm); +} +static struct kobj_attribute pmadv_ksm_attr = __ATTR_RO(ksm); + +static struct attribute *pmadv_sysfs_attrs[] = { + &pmadv_ksm_attr.attr, + NULL, +}; + +static const struct attribute_group pmadv_sysfs_attr_group = { + .attrs = pmadv_sysfs_attrs, + .name = "pmadv", +}; + +static int __init pmadv_sysfs_init(void) +{ + return sysfs_create_group(kernel_kobj, &pmadv_sysfs_attr_group); +} +subsys_initcall(pmadv_sysfs_init); +#endif /* CONFIG_KSM */ -- 2.40.0.71.g950264636c