[PATCH v2 22/28] um: Add UML_SECCOMP configuration option

[benjamin at sipsolutions.net]

From: Benjamin Berg <benjamin at sipsolutions.net>

Add the UML_SECCOMP configuration options. The next commits will add the
support itself in smaller chunks.

Only x86_64 will be supported for now.

Signed-off-by: Benjamin Berg <benjamin at sipsolutions.net>
---
 arch/um/Kconfig | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 78de31ac1da7..e67c6402dd4b 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -234,6 +234,25 @@ config KASAN_SHADOW_OFFSET
 	  set to a large value. On low-memory systems, try 0x7fff8000, as it fits
 	  into the immediate of most instructions, improving performance.
 
+config UML_SECCOMP
+	bool "seccomp based process tracing"
+	default n
+	depends on 64BIT
+	help
+	  Enable this option will enable seccomp based tracing of processes.
+
+	  UML must call syscalls from within the userspace processes when
+	  mapping physical memory in response to page faults. Using seccomp
+	  based tracing permits delaying these host syscalls until userspace
+	  processes are resumed in order to run a task, thereby avoiding
+	  overhead for the host by saving context switches.
+
+	  This feature speeds up e.g. fork() heavy workloads considerably.
+	  However, the current implementation is not safe as userspace
+	  processes can trigger any syscall to the host OS.
+
+	  If in doubt say N, as the feature has security implications.
+
 endmenu
 
 source "arch/um/drivers/Kconfig"
-- 
2.38.1