Implement seccomp decoding

* configure.ac (AC_CHECK_HEADERS): Add linux/filter.h
and linux/seccomp.h.
* defs.h (print_seccomp_filter): New prototype.
* linux/dummy.h (sys_seccomp): Remove.
* linux/syscall.h (sys_seccomp): New prototype.
* prctl.c: Include <linux/seccomp.h>.
(sys_prctl): Decode PR_SET_SECCOMP.
* seccomp.c: New file.
* Makefile.am (strace_SOURCES): Add it.
* xlat/bpf_class.in: New file.
* xlat/bpf_miscop.in: Likewise.
* xlat/bpf_mode.in: Likewise.
* xlat/bpf_op_alu.in: Likewise.
* xlat/bpf_op_jmp.in: Likewise.
* xlat/bpf_rval.in: Likewise.
* xlat/bpf_size.in: Likewise.
* xlat/bpf_src.in: Likewise.
* xlat/seccomp_filter_flags.in: Likewise.
* xlat/seccomp_mode.in: Likewise.
* xlat/seccomp_ops.in: Likewise.
* xlat/seccomp_ret_action.in: Likewise.

Makefile.am

@@ -86,6 +86,7 @@ strace_SOURCES =	\
 	resource.c	\
 	sched.c		\
 	scsi.c		\
+	seccomp.c	\
 	signal.c	\
 	sock.c		\
 	socketutils.c	\

configure.ac

@@ -223,11 +223,13 @@ AC_CHECK_HEADERS(m4_normalize([
 	inttypes.h
 	ioctls.h
 	linux/falloc.h
+	linux/filter.h
 	linux/hiddev.h
 	linux/input.h
 	linux/mmtimer.h
 	linux/perf_event.h
 	linux/ptrace.h
+	linux/seccomp.h
 	linux/utsname.h
 	mqueue.h
 	netinet/sctp.h

defs.h

@@ -734,6 +734,7 @@ extern void tprint_iov_upto(struct tcb *, unsigned long, unsigned long, int deco
 extern void tprint_open_modes(int);
 extern const char *sprint_open_modes(int);
 extern void print_loff_t(struct tcb *, long);
+extern void print_seccomp_filter(struct tcb *tcp, unsigned long);
 
 extern const struct_ioctlent *ioctl_lookup(const unsigned int);
 extern const struct_ioctlent *ioctl_next_match(const struct_ioctlent *);

linux/dummy.h

@@ -44,7 +44,6 @@
 #define	sys_open_by_handle_at	printargs
 #define	sys_sched_getattr	printargs
 #define	sys_sched_setattr	printargs
-#define	sys_seccomp		printargs
 #define	sys_sysfs		printargs
 #define	sys_vm86		printargs
 #define	sys_vm86old		printargs

linux/syscall.h

@@ -222,6 +222,7 @@ int sys_sched_rr_get_interval();
 int sys_sched_setaffinity();
 int sys_sched_setparam();
 int sys_sched_setscheduler();
+int sys_seccomp();
 int sys_select();
 int sys_semctl();
 int sys_semget();

prctl.c

@@ -25,6 +25,12 @@ unalignctl_string(unsigned int ctl)
 	return buf;
 }
 
+#ifdef HAVE_LINUX_SECCOMP_H
+# include <linux/seccomp.h>
+#endif
+
+#include "xlat/seccomp_mode.h"
+
 int
 sys_prctl(struct tcb *tcp)
 {
@@ -74,6 +80,28 @@ sys_prctl(struct tcb *tcp)
 		case PR_GET_KEEPCAPS:
 			break;
 #endif
+
+#ifdef PR_SET_SECCOMP
+		case PR_SET_SECCOMP:
+			tprints(", ");
+			printxval(seccomp_mode, tcp->u_arg[1],
+				  "SECCOMP_MODE_???");
+# ifdef SECCOMP_MODE_STRICT
+			if (SECCOMP_MODE_STRICT == tcp->u_arg[1])
+				break;
+# endif
+# ifdef SECCOMP_MODE_FILTER
+			if (SECCOMP_MODE_FILTER == tcp->u_arg[1]) {
+				tprints(", ");
+				print_seccomp_filter(tcp, tcp->u_arg[2]);
+				break;
+			}
+# endif
+			for (i = 2; i < tcp->s_ent->nargs; i++)
+				tprintf(", %#lx", tcp->u_arg[i]);
+			break;
+#endif /* PR_SET_SECCOMP */
+
 		default:
 			for (i = 1; i < tcp->s_ent->nargs; i++)
 				tprintf(", %#lx", tcp->u_arg[i]);

seccomp.c

@@ -0,0 +1,264 @@
+/*
+ * Copyright (c) 2015 Dmitry V. Levin <ldv@altlinux.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "defs.h"
+
+#ifdef HAVE_LINUX_SECCOMP_H
+# include <linux/seccomp.h>
+#endif
+
+#ifndef SECCOMP_SET_MODE_STRICT
+# define SECCOMP_SET_MODE_STRICT 1
+#endif
+#ifndef SECCOMP_SET_MODE_FILTER
+# define SECCOMP_SET_MODE_FILTER 1
+#endif
+#include "xlat/seccomp_ops.h"
+
+#ifndef SECCOMP_FILTER_FLAG_TSYNC
+# define SECCOMP_FILTER_FLAG_TSYNC 1
+#endif
+#include "xlat/seccomp_filter_flags.h"
+
+#ifdef HAVE_LINUX_FILTER_H
+# include <linux/filter.h>
+# include "xlat/bpf_class.h"
+# include "xlat/bpf_miscop.h"
+# include "xlat/bpf_mode.h"
+# include "xlat/bpf_op_alu.h"
+# include "xlat/bpf_op_jmp.h"
+# include "xlat/bpf_rval.h"
+# include "xlat/bpf_size.h"
+# include "xlat/bpf_src.h"
+
+# ifndef SECCOMP_RET_ACTION
+#  define SECCOMP_RET_ACTION 0x7fff0000U
+# endif
+# include "xlat/seccomp_ret_action.h"
+#endif
+
+struct bpf_filter {
+	uint16_t code;
+	uint8_t jt;
+	uint8_t jf;
+	uint32_t k;
+};
+
+#ifdef HAVE_LINUX_FILTER_H
+
+static void
+decode_bpf_code(uint16_t code)
+{
+	uint16_t i = code & ~BPF_CLASS(code);
+
+	printxval(bpf_class, BPF_CLASS(code), "BPF_???");
+	switch (BPF_CLASS(code)) {
+		case BPF_LD:
+		case BPF_LDX:
+			tprints(" | ");
+			printxval(bpf_size, BPF_SIZE(code), "BPF_???");
+			tprints(" | ");
+			printxval(bpf_mode, BPF_MODE(code), "BPF_???");
+			break;
+		case BPF_ST:
+		case BPF_STX:
+			if (i)
+				tprintf(" | %#x /* %s */", i, "BPF_???");
+			break;
+		case BPF_ALU:
+			tprints(" | ");
+			printxval(bpf_src, BPF_SRC(code), "BPF_???");
+			tprints(" | ");
+			printxval(bpf_op_alu, BPF_OP(code), "BPF_???");
+			break;
+		case BPF_JMP:
+			tprints(" | ");
+			printxval(bpf_src, BPF_SRC(code), "BPF_???");
+			tprints(" | ");
+			printxval(bpf_op_jmp, BPF_OP(code), "BPF_???");
+			break;
+		case BPF_RET:
+			tprints(" | ");
+			printxval(bpf_rval, BPF_RVAL(code), "BPF_???");
+			i &= ~BPF_RVAL(code);
+			if (i)
+				tprintf(" | %#x /* %s */", i, "BPF_???");
+			break;
+		case BPF_MISC:
+			tprints(" | ");
+			printxval(bpf_miscop, BPF_MISCOP(code), "BPF_???");
+			i &= ~BPF_MISCOP(code);
+			if (i)
+				tprintf(" | %#x /* %s */", i, "BPF_???");
+			break;
+	}
+
+}
+
+static void
+decode_bpf_stmt(const struct bpf_filter *filter)
+{
+#ifdef HAVE_LINUX_FILTER_H
+	tprints("BPF_STMT(");
+	decode_bpf_code(filter->code);
+	tprints(", ");
+	if (BPF_CLASS(filter->code) == BPF_RET) {
+		unsigned int action = SECCOMP_RET_ACTION & filter->k;
+		unsigned int data = filter->k & ~action;
+
+		printxval(seccomp_ret_action, action, "SECCOMP_RET_???");
+		if (data)
+			tprintf(" | %#x)", data);
+		else
+			tprints(")");
+	} else {
+		tprintf("%#x)", filter->k);
+	}
+#else
+	tprintf("BPF_STMT(%#x, %#x)", filter->code, filter->k);
+#endif /* HAVE_LINUX_FILTER_H */
+}
+
+static void
+decode_bpf_jump(const struct bpf_filter *filter)
+{
+#ifdef HAVE_LINUX_FILTER_H
+	tprints("BPF_JUMP(");
+	decode_bpf_code(filter->code);
+	tprintf(", %#x, %#x, %#x)",
+		filter->k, filter->jt, filter->jf);
+#else
+	tprintf("BPF_JUMP(%#x, %#x, %#x, %#x)",
+		filter->code, filter->k, filter->jt, filter->jf);
+#endif /* HAVE_LINUX_FILTER_H */
+}
+
+static void
+decode_filter(const struct bpf_filter *filter)
+{
+	if (filter->jt || filter->jf)
+		decode_bpf_jump(filter);
+	else
+		decode_bpf_stmt(filter);
+}
+
+#endif /* HAVE_LINUX_FILTER_H */
+
+#ifndef BPF_MAXINSNS
+# define BPF_MAXINSNS 4096
+#endif
+
+static void
+decode_fprog(struct tcb *tcp, unsigned short len, unsigned long addr)
+{
+	if (!len || abbrev(tcp)) {
+		tprintf("{len = %u, filter = %#lx}", len, addr);
+	} else {
+		unsigned int i = 0;
+
+		tprints("[");
+		while (i < len && i < BPF_MAXINSNS) {
+			struct bpf_filter filter;
+
+			if (umove(tcp, addr, &filter) < 0)
+				break;
+			if (i)
+				tprints(", ");
+			decode_filter(&filter);
+
+			addr += sizeof(filter);
+			++i;
+		}
+		if (i < len)
+			tprints("...");
+		tprints("]");
+	}
+}
+
+void
+print_seccomp_filter(struct tcb *tcp, unsigned long addr)
+{
+	if (addr) {
+#if SUPPORTED_PERSONALITIES > 1 && SIZEOF_LONG > 4
+		if (current_wordsize == 4) {
+			struct {
+				unsigned short len;
+				uint32_t filter;
+			} fprog;
+			if (umove(tcp, addr, &fprog) < 0)
+				tprintf("%#lx", addr);
+			else
+				decode_fprog(tcp, fprog.len, fprog.filter);
+		} else {
+#endif
+			struct {
+				unsigned short len;
+				unsigned long filter;
+			} fprog;
+			if (umove(tcp, addr, &fprog) < 0)
+				tprintf("%#lx", addr);
+			else
+				decode_fprog(tcp, fprog.len, fprog.filter);
+#if SUPPORTED_PERSONALITIES > 1 && SIZEOF_LONG > 4
+		}
+#endif
+	} else {
+		tprints("NULL");
+	}
+}
+
+static void
+decode_seccomp_set_mode_strict(unsigned int flags, unsigned long addr)
+{
+	tprintf("%u, ", flags);
+	if (addr)
+		tprintf("%#lx", addr);
+	else
+		tprints("NULL");
+}
+
+int
+sys_seccomp(struct tcb *tcp)
+{
+	if (entering(tcp)) {
+		unsigned int op = tcp->u_arg[0];
+
+		printxval(seccomp_ops, op, "SECCOMP_SET_MODE_???");
+		tprints(", ");
+
+		if (op == SECCOMP_SET_MODE_FILTER) {
+			printflags(seccomp_filter_flags, tcp->u_arg[1],
+				   "SECCOMP_FILTER_FLAG_???");
+			tprints(", ");
+			print_seccomp_filter(tcp, tcp->u_arg[2]);
+		} else {
+			decode_seccomp_set_mode_strict(tcp->u_arg[1],
+						       tcp->u_arg[2]);
+		}
+	}
+	return 0;
+}

xlat/bpf_class.in

@@ -0,0 +1,8 @@
+BPF_LD
+BPF_LDX
+BPF_ST
+BPF_STX
+BPF_ALU
+BPF_JMP
+BPF_RET
+BPF_MISC

xlat/bpf_miscop.in

@@ -0,0 +1,2 @@
+BPF_TAX
+BPF_TXA

xlat/bpf_mode.in

@@ -0,0 +1,7 @@
+BPF_IMM
+BPF_ABS
+BPF_IND
+BPF_MEM
+BPF_LEN
+BPF_MSH
+BPF_XADD

xlat/bpf_op_alu.in

@@ -0,0 +1,13 @@
+BPF_ADD
+BPF_SUB
+BPF_MUL
+BPF_DIV
+BPF_OR
+BPF_AND
+BPF_LSH
+BPF_RSH
+BPF_NEG
+BPF_MOD
+BPF_XOR
+BPF_MOV
+BPF_ARSH

xlat/bpf_op_jmp.in

@@ -0,0 +1,10 @@
+BPF_JA
+BPF_JEQ
+BPF_JGT
+BPF_JGE
+BPF_JSET
+BPF_JNE
+BPF_JSGT
+BPF_JSGE
+BPF_CALL
+BPF_EXIT

xlat/bpf_rval.in

@@ -0,0 +1,3 @@
+BPF_K
+BPF_X
+BPF_A

xlat/bpf_size.in

@@ -0,0 +1,4 @@
+BPF_W
+BPF_H
+BPF_B
+BPF_DW

xlat/bpf_src.in

@@ -0,0 +1,2 @@
+BPF_K
+BPF_X

xlat/seccomp_filter_flags.in

@@ -0,0 +1 @@
+SECCOMP_FILTER_FLAG_TSYNC

xlat/seccomp_mode.in

@@ -0,0 +1,3 @@
+SECCOMP_MODE_DISABLED
+SECCOMP_MODE_STRICT
+SECCOMP_MODE_FILTER

xlat/seccomp_ops.in

@@ -0,0 +1,2 @@
+SECCOMP_SET_MODE_STRICT
+SECCOMP_SET_MODE_FILTER

xlat/seccomp_ret_action.in

@@ -0,0 +1,5 @@
+SECCOMP_RET_KILL
+SECCOMP_RET_TRAP
+SECCOMP_RET_ERRNO
+SECCOMP_RET_TRACE
+SECCOMP_RET_ALLOW