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[2003:cd:df17:9b70:f8b:32cb:72fe:aa13]) by smtp.gmail.com with ESMTPSA id r17-20020a50aad1000000b0053e2a64b5f8sm3381499edc.14.2023.10.28.13.41.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 28 Oct 2023 13:41:05 -0700 (PDT) From: York Jasper Niebuhr To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, York Jasper Niebuhr Subject: [PATCH] Added empty sys_ememz Date: Sat, 28 Oct 2023 22:40:46 +0200 Message-Id: <20231028204046.11258-1-yjnworkstation@gmail.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" --- arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + include/linux/syscalls.h | 1 + include/uapi/asm-generic/unistd.h | 5 ++++- kernel/sys_ni.c | 3 +++ mm/Kconfig | 7 +++++++ mm/ememz.c | 18 ++++++++++++++++++ 7 files changed, 35 insertions(+), 1 deletion(-) create mode 100644 mm/ememz.c diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscal= ls/syscall_32.tbl index 2d0b1bd866ea..7803b2303da4 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -457,3 +457,4 @@ 450 i386 set_mempolicy_home_node sys_set_mempolicy_home_node 451 i386 cachestat sys_cachestat 452 i386 fchmodat2 sys_fchmodat2 +453 i386 ememz sys_ememz diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscal= ls/syscall_64.tbl index 1d6eee30eceb..39530de435e1 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -375,6 +375,7 @@ 451 common cachestat sys_cachestat 452 common fchmodat2 sys_fchmodat2 453 64 map_shadow_stack sys_map_shadow_stack +454 common ememz sys_ememz =20 # # Due to a historical design error, certain syscalls are numbered differen= tly diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 22bc6bc147f8..4127689798e2 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -940,6 +940,7 @@ asmlinkage long sys_cachestat(unsigned int fd, struct cachestat_range __user *cstat_range, struct cachestat __user *cstat, unsigned int flags); asmlinkage long sys_map_shadow_stack(unsigned long addr, unsigned long siz= e, unsigned int flags); +asmlinkage long sys_ememz(int flags); =20 /* * Architecture-specific system calls diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/u= nistd.h index abe087c53b4b..63ec7611af63 100644 --- a/include/uapi/asm-generic/unistd.h +++ b/include/uapi/asm-generic/unistd.h @@ -823,8 +823,11 @@ __SYSCALL(__NR_cachestat, sys_cachestat) #define __NR_fchmodat2 452 __SYSCALL(__NR_fchmodat2, sys_fchmodat2) =20 +#define __NR_ememz 453 +__SYSCALL(__NR_ememz, sys_ememz) + #undef __NR_syscalls -#define __NR_syscalls 453 +#define __NR_syscalls 454 =20 /* * 32 bit systems traditionally used different diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index e137c1385c56..108ff4c6113c 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -253,6 +253,9 @@ COND_SYSCALL(pkey_free); /* memfd_secret */ COND_SYSCALL(memfd_secret); =20 +/* ememz */ +COND_SYSCALL(ememz); + /* * Architecture specific weak syscall entries. */ diff --git a/mm/Kconfig b/mm/Kconfig index 264a2df5ecf5..dd4d505cf52e 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -1260,4 +1260,11 @@ config LOCK_MM_AND_FIND_VMA =20 source "mm/damon/Kconfig" =20 +config EMEMZ_SYSCALL + bool "Ememz syscall" if EXPERT + default y + help + sys_ememz is a system call to flag a process' memory to be filled + with zeros on exit. + endmenu diff --git a/mm/ememz.c b/mm/ememz.c new file mode 100644 index 000000000000..d7765375122a --- /dev/null +++ b/mm/ememz.c @@ -0,0 +1,18 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +#ifdef CONFIG_EMEMZ_SYSCALL +/* + * Set task_struct flag to fill any memory associated with process on + * exit to zero. + */ +SYSCALL_DEFINE1(ememz, int, flags) +{ + if (flags & ~(0)) + return -EINVAL; + + // Set flag atomically + return 0; +} +#endif --=20 2.34.1 Hi, I am looking for a more fine grained alternative with less system overhead to CONFIG_INIT_ON_FREE_DEFAULT_ON. My idea was to add a system call (ememz) to set a flag in the task_struct that causes initialization of all a process' pages on exit. Are there already any other alternatives I should consider and is this the proper way to go on with it? Any suggestions are welcome. Signed-off-by: York Jasper Niebuhr