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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id i7-20020a05620a0a0700b006fbbdc6c68fsm1411163qka.68.2023.01.26.11.06.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Jan 2023 11:06:48 -0800 (PST) From: Gregory Price X-Google-Original-From: Gregory Price To: linux-kernel@vger.kernel.org Cc: linux-doc@vger.kernel.org, oleg@redhat.com, avagin@gmail.com, peterz@infradead.org, luto@kernel.org, krisman@collabora.com, tglx@linutronix.de, corbet@lwn.net, shuah@kernel.org, Gregory Price Subject: [PATCH v7 1/1] ptrace,syscall_user_dispatch: checkpoint/restore support for SUD Date: Thu, 26 Jan 2023 14:06:45 -0500 Message-Id: <20230126190645.18341-2-gregory.price@memverge.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230126190645.18341-1-gregory.price@memverge.com> References: <20230126190645.18341-1-gregory.price@memverge.com> 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" Implement ptrace getter/setter interface for syscall user dispatch. These prctl settings are presently write-only, making it impossible to implement transparent checkpoint/restore via software like CRIU. 'on_dispatch' field is not exposed because it is a kernel-internal only field that cannot be 'true' when returning to userland. Signed-off-by: Gregory Price Reviewed-by: Oleg Nesterov --- .../admin-guide/syscall-user-dispatch.rst | 5 ++- include/linux/syscall_user_dispatch.h | 18 +++++++++ include/uapi/linux/ptrace.h | 9 +++++ kernel/entry/syscall_user_dispatch.c | 39 +++++++++++++++++++ kernel/ptrace.c | 9 +++++ 5 files changed, 79 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/syscall-user-dispatch.rst b/Document= ation/admin-guide/syscall-user-dispatch.rst index 60314953c728..a23ae21a1d5b 100644 --- a/Documentation/admin-guide/syscall-user-dispatch.rst +++ b/Documentation/admin-guide/syscall-user-dispatch.rst @@ -43,7 +43,10 @@ doesn't rely on any of the syscall ABI to make the filte= ring. It uses only the syscall dispatcher address and the userspace key. =20 As the ABI of these intercepted syscalls is unknown to Linux, these -syscalls are not instrumentable via ptrace or the syscall tracepoints. +syscalls are not instrumentable via ptrace or the syscall tracepoints, +however an interfaces to suspend, checkpoint, and restore syscall user +dispatch configuration has been added to ptrace to assist userland +checkpoint/restart software. =20 Interface --------- diff --git a/include/linux/syscall_user_dispatch.h b/include/linux/syscall_= user_dispatch.h index a0ae443fb7df..5de2d64ace19 100644 --- a/include/linux/syscall_user_dispatch.h +++ b/include/linux/syscall_user_dispatch.h @@ -22,6 +22,12 @@ int set_syscall_user_dispatch(unsigned long mode, unsign= ed long offset, #define clear_syscall_work_syscall_user_dispatch(tsk) \ clear_task_syscall_work(tsk, SYSCALL_USER_DISPATCH) =20 +int syscall_user_dispatch_get_config(struct task_struct *task, unsigned lo= ng size, + void __user *data); + +int syscall_user_dispatch_set_config(struct task_struct *task, unsigned lo= ng size, + void __user *data); + #else struct syscall_user_dispatch {}; =20 @@ -35,6 +41,18 @@ static inline void clear_syscall_work_syscall_user_dispa= tch(struct task_struct * { } =20 +static inline int syscall_user_dispatch_get_config(struct task_struct *tas= k, unsigned long size, + void __user *data) +{ + return -EINVAL; +} + +static inline int syscall_user_dispatch_set_config(struct task_struct *tas= k, unsigned long size, + void __user *data) +{ + return -EINVAL; +} + #endif /* CONFIG_GENERIC_ENTRY */ =20 #endif /* _SYSCALL_USER_DISPATCH_H */ diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h index 195ae64a8c87..6d2f3b86f932 100644 --- a/include/uapi/linux/ptrace.h +++ b/include/uapi/linux/ptrace.h @@ -112,6 +112,15 @@ struct ptrace_rseq_configuration { __u32 pad; }; =20 +#define PTRACE_SET_SYSCALL_USER_DISPATCH_CONFIG 0x4210 +#define PTRACE_GET_SYSCALL_USER_DISPATCH_CONFIG 0x4211 +struct syscall_user_dispatch_config { + __u64 mode; + __s8 *selector; + __u64 offset; + __u64 len; +}; + /* * These values are stored in task->ptrace_message * by ptrace_stop to describe the current syscall-stop. diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_us= er_dispatch.c index 0b6379adff6b..26217fcc1c90 100644 --- a/kernel/entry/syscall_user_dispatch.c +++ b/kernel/entry/syscall_user_dispatch.c @@ -106,3 +106,42 @@ int set_syscall_user_dispatch(unsigned long mode, unsi= gned long offset, =20 return 0; } + +int syscall_user_dispatch_get_config(struct task_struct *task, unsigned lo= ng size, + void __user *data) +{ + struct syscall_user_dispatch *sd =3D &task->syscall_dispatch; + struct syscall_user_dispatch_config config; + + if (size !=3D sizeof(struct syscall_user_dispatch_config)) + return -EINVAL; + + if (test_syscall_work(SYSCALL_USER_DISPATCH)) + config.mode =3D PR_SYS_DISPATCH_ON; + else + config.mode =3D PR_SYS_DISPATCH_OFF; + + config.offset =3D sd->offset; + config.len =3D sd->len; + config.selector =3D sd->selector; + + if (copy_to_user(data, &config, sizeof(config))) + return -EFAULT; + + return 0; +} + +int syscall_user_dispatch_set_config(struct task_struct *task, unsigned lo= ng size, + void __user *data) +{ + struct syscall_user_dispatch_config config; + + if (size !=3D sizeof(struct syscall_user_dispatch_config)) + return -EINVAL; + + if (copy_from_user(&config, data, sizeof(config))) + return -EFAULT; + + return set_syscall_user_dispatch(config.mode, config.offset, config.len, + config.selector); +} diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 54482193e1ed..d99376532b56 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -32,6 +32,7 @@ #include #include #include +#include =20 #include /* for syscall_get_* */ =20 @@ -1259,6 +1260,14 @@ int ptrace_request(struct task_struct *child, long r= equest, break; #endif =20 + case PTRACE_SET_SYSCALL_USER_DISPATCH_CONFIG: + ret =3D syscall_user_dispatch_set_config(child, addr, datavp); + break; + + case PTRACE_GET_SYSCALL_USER_DISPATCH_CONFIG: + ret =3D syscall_user_dispatch_get_config(child, addr, datavp); + break; + default: break; } --=20 2.39.0