diff mbox series

[v6,2/9] kernel: entry: Support TIF_SYSCAL_INTERCEPT on common entry code

Message ID 20200904203147.2908430-3-krisman@collabora.com
State New
Headers show
Series Syscall User Dispatch | expand

Commit Message

Gabriel Krisman Bertazi Sept. 4, 2020, 8:31 p.m. UTC
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 <krisman@collabora.com>
---
 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(-)

Comments

Christian Brauner Sept. 7, 2020, 10:16 a.m. UTC | #1
On Fri, Sep 04, 2020 at 04:31:40PM -0400, Gabriel Krisman Bertazi wrote:
> 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 <krisman@collabora.com>
> ---
>  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 fcae019158ca..44fd089d59da 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)

Hey Gabriel,

I think you can drop the pt_regs argument and just have this be

static inline do_syscall_intercept(void)

otherwise

Acked-by: Christian Brauner <christian.brauner@ubuntu.com>

> +{
> +	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
Peter Zijlstra Sept. 11, 2020, 9:35 a.m. UTC | #2
On Fri, Sep 04, 2020 at 04:31:40PM -0400, Gabriel Krisman Bertazi wrote:
> 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

Why doesn't this add:

#ifndef _TIF_SYSCALL_INTERCEPT
#define _TIF_SYSCALL_INTERCEPT		(0)
#endif

?
Gabriel Krisman Bertazi Sept. 11, 2020, 8:11 p.m. UTC | #3
peterz@infradead.org writes:

> On Fri, Sep 04, 2020 at 04:31:40PM -0400, Gabriel Krisman Bertazi wrote:
>> 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
>
> Why doesn't this add:
>
> #ifndef _TIF_SYSCALL_INTERCEPT
> #define _TIF_SYSCALL_INTERCEPT		(0)
> #endif
>

I will add in the next version.  Thanks!
diff mbox series

Patch

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 fcae019158ca..44fd089d59da 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;
 	}