Syscalls that use common entry code (x86 at the moment of this writing) need to have their defines updated inside this commit. This added a measureable overhead of 1ns to seccomp_benchmark selftests on a bare-metal AMD system.
Signed-off-by: Gabriel Krisman Bertazi <[email protected]> --- arch/x86/include/asm/thread_info.h | 4 ++-- include/linux/entry-common.h | 6 +----- kernel/entry/common.c | 24 +++++++++++++++++++++--- 3 files changed, 24 insertions(+), 10 deletions(-) diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index 267701ae3d86..cf723181e1f2 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -82,7 +82,7 @@ struct thread_info { #define TIF_SSBD 5 /* Speculative store bypass disable */ #define TIF_SYSCALL_EMU 6 /* syscall emulation active */ #define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */ -#define TIF_SECCOMP 8 /* secure computing */ +#define TIF_SYSCALL_INTERCEPT 8 /* Intercept system call */ #define TIF_SPEC_IB 9 /* Indirect branch speculation mitigation */ #define TIF_SPEC_FORCE_UPDATE 10 /* Force speculation MSR update in context switch */ #define TIF_USER_RETURN_NOTIFY 11 /* notify kernel of userspace return */ @@ -112,7 +112,7 @@ struct thread_info { #define _TIF_SSBD (1 << TIF_SSBD) #define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU) #define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT) -#define _TIF_SECCOMP (1 << TIF_SECCOMP) +#define _TIF_SYSCALL_INTERCEPT (1 << TIF_SYSCALL_INTERCEPT) #define _TIF_SPEC_IB (1 << TIF_SPEC_IB) #define _TIF_SPEC_FORCE_UPDATE (1 << TIF_SPEC_FORCE_UPDATE) #define _TIF_USER_RETURN_NOTIFY (1 << TIF_USER_RETURN_NOTIFY) diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h index efebbffcd5cc..72ce9ca860c6 100644 --- a/include/linux/entry-common.h +++ b/include/linux/entry-common.h @@ -21,10 +21,6 @@ # define _TIF_SYSCALL_TRACEPOINT (0) #endif -#ifndef _TIF_SECCOMP -# define _TIF_SECCOMP (0) -#endif - #ifndef _TIF_SYSCALL_AUDIT # define _TIF_SYSCALL_AUDIT (0) #endif @@ -45,7 +41,7 @@ #endif #define SYSCALL_ENTER_WORK \ - (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \ + (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SYSCALL_INTERCEPT | \ _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_EMU | \ ARCH_SYSCALL_ENTER_WORK) diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 9852e0d62d95..80db3f146462 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -4,6 +4,7 @@ #include <linux/entry-common.h> #include <linux/livepatch.h> #include <linux/audit.h> +#include <linux/syscall_intercept.h> #define CREATE_TRACE_POINTS #include <trace/events/syscalls.h> @@ -41,6 +42,20 @@ static inline void syscall_enter_audit(struct pt_regs *regs, long syscall) } } +static inline long do_syscall_intercept(struct pt_regs *regs) +{ + int sysint_work = READ_ONCE(current->syscall_intercept); + int ret; + + if (sysint_work & SYSINT_SECCOMP) { + ret = __secure_computing(NULL); + if (ret == -1L) + return ret; + } + + return 0; +} + static long syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long ti_work) { @@ -53,9 +68,12 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall, return -1L; } - /* Do seccomp after ptrace, to catch any tracer changes. */ - if (ti_work & _TIF_SECCOMP) { - ret = __secure_computing(NULL); + /* + * Do syscall interception like seccomp after ptrace, to catch + * any tracer changes. + */ + if (ti_work & _TIF_SYSCALL_INTERCEPT) { + ret = do_syscall_intercept(regs); if (ret == -1L) return ret; } -- 2.28.0
