[PATCH 2/2] RISC-V: Add support for SECCOMP

Palmer Dabbelt
2018-10-24T20:40:36Z

From: "Wesley W. Terpstra" <wesley@sifive.com>

This is a fairly straight-forward implementation of seccomp for RISC-V
systems.

Signed-off-by: Wesley W. Terpstra <wesley@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
---
arch/riscv/Kconfig | 18 ++++++++++++++++++
arch/riscv/include/asm/seccomp.h | 10 ++++++++++
arch/riscv/include/asm/syscall.h | 6 ++++++
arch/riscv/include/asm/thread_info.h | 1 +
include/uapi/linux/audit.h | 1 +
5 files changed, 36 insertions(+)
create mode 100644 arch/riscv/include/asm/seccomp.h

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a344980287a5..28abe47602a1 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -28,6 +28,7 @@ config RISCV
select GENERIC_STRNLEN_USER
select GENERIC_SMP_IDLE_THREAD
select GENERIC_ATOMIC64 if !64BIT || !RISCV_ISA_A
+ select HAVE_ARCH_SECCOMP_FILTER
select HAVE_MEMBLOCK
select HAVE_MEMBLOCK_NODE_MAP
select HAVE_DMA_CONTIGUOUS
@@ -214,6 +215,22 @@ menu "Kernel type"

source "kernel/Kconfig.hz"

+config SECCOMP
+ bool "Enable seccomp to safely compute untrusted bytecode"
+
+ help
+ This kernel feature is useful for number crunching applications
+ that may need to compute untrusted bytecode during their
+ execution. By using pipes or other transports made available to
+ the process as file descriptors supporting the read/write
+ syscalls, it's possible to isolate those applications in
+ their own address space using seccomp. Once seccomp is
+ enabled via prctl(PR_SET_SECCOMP), it cannot be disabled
+ and the task is only allowed to execute a few safe syscalls
+ defined by each seccomp mode.
+
+ If unsure, say Y. Only embedded should say N here.
+
endmenu

menu "Bus support"
@@ -243,3 +260,4 @@ menu "Power management options"
source kernel/power/Kconfig

endmenu
+
diff --git a/arch/riscv/include/asm/seccomp.h b/arch/riscv/include/asm/seccomp.h
new file mode 100644
index 000000000000..c1b4407f1038
--- /dev/null
+++ b/arch/riscv/include/asm/seccomp.h
@@ -0,0 +1,10 @@
+/* Copyright 2018 SiFive, Inc. */
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_RISCV_SECCOMP_H
+#define _ASM_RISCV_SECCOMP_H
+
+#include <asm/unistd.h>
+
+#include <asm-generic/seccomp.h>
+
+#endif /* _ASM_RISCV_SECCOMP_H */
diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h
index 8d25f8904c00..d24f774f39df 100644
--- a/arch/riscv/include/asm/syscall.h
+++ b/arch/riscv/include/asm/syscall.h
@@ -19,6 +19,7 @@
#define _ASM_RISCV_SYSCALL_H

#include <linux/sched.h>
+#include <uapi/linux/audit.h>
#include <linux/err.h>

/* The array of function pointers for syscalls. */
@@ -99,4 +100,9 @@ static inline void syscall_set_arguments(struct task_struct *task,
memcpy(&regs->a1 + i * sizeof(regs->a1), args, n * sizeof(regs->a0));
}

+static inline int syscall_get_arch(void)
+{
+ return AUDIT_ARCH_RISCV;
+}
+
#endif /* _ASM_RISCV_SYSCALL_H */
diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index f8fa1cd2dad9..374973dc05c6 100644
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -80,6 +80,7 @@ struct thread_info {
#define TIF_RESTORE_SIGMASK 4 /* restore signal mask in do_signal() */
#define TIF_MEMDIE 5 /* is terminating due to OOM killer */
#define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */
+#define TIF_SECCOMP 7 /* seccomp syscall filtering active */

#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 818ae690ab79..c16fa1a76659 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -399,6 +399,7 @@ enum {
/* do not define AUDIT_ARCH_PPCLE since it is not supported by audit */
#define AUDIT_ARCH_PPC64 (EM_PPC64|__AUDIT_ARCH_64BIT)
#define AUDIT_ARCH_PPC64LE (EM_PPC64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
+#define AUDIT_ARCH_RISCV (EM_RISCV)
#define AUDIT_ARCH_S390 (EM_S390)
#define AUDIT_ARCH_S390X (EM_S390|__AUDIT_ARCH_64BIT)
#define AUDIT_ARCH_SH (EM_SH)
--
2.18.1