Implement PTRACE_SECCOMP_GET_METADATA ptrace request decoding

* defs.h (seccomp_filter_flags): New declaration.
* process.c (SYS_FUNC(ptrace)): Implement PTRACE_SECCOMP_GET_METADATA
request decoding.
* ptrace.h [!PTRACE_SECCOMP_GET_METADATA] (PTRACE_SECCOMP_GET_METADATA):
New macro constant.
* xlat/ptrace_cmds.in (PTRACE_SECCOMP_GET_METADATA): New constant.
* tests/ptrace.c (main): Add some checks for PTRACE_SECCOMP_GET_METADATA
request decoding.
* NEWS: Mention it.

Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>

NEWS

@@ -11,6 +11,7 @@ Noteworthy changes in release ?.?? (????-??-??)
 * Improvements
   * IPv6 addresses shown in socket information in -yy mode are now printed
     in brackets.
+  * Enhanced decoding of ptrace syscall.
   * Enhanced NETLINK_ROUTE protocol decoding.
   * Updated lists of signal codes.
   * Updated lists of BPF_*, BTN_*, ETH_P_*, INET_DIAG_BC_*, KEY_*, POLL*, RWF_*,

defs.h

@@ -297,6 +297,7 @@ extern const struct xlat resource_flags[];
 extern const struct xlat routing_scopes[];
 extern const struct xlat routing_table_ids[];
 extern const struct xlat routing_types[];
+extern const struct xlat seccomp_filter_flags[];
 extern const struct xlat seccomp_ret_action[];
 extern const struct xlat setns_types[];
 extern const struct xlat sg_io_info[];

process.c

@@ -122,6 +122,7 @@ SYS_FUNC(ptrace)
 		case PTRACE_GETSIGMASK:
 		case PTRACE_SETSIGMASK:
 		case PTRACE_SECCOMP_GET_FILTER:
+		case PTRACE_SECCOMP_GET_METADATA:
 			tprintf(", %" PRI_klu, addr);
 			break;
 		case PTRACE_PEEKSIGINFO: {
@@ -204,6 +205,21 @@ SYS_FUNC(ptrace)
 		case PTRACE_SETREGSET:
 			tprint_iov(tcp, /*len:*/ 1, data, IOV_DECODE_ADDR);
 			break;
+		case PTRACE_SECCOMP_GET_METADATA:
+			if (verbose(tcp)) {
+				uint64_t filter_off;
+				if (addr < sizeof(filter_off) ||
+				    umove(tcp, data, &filter_off)) {
+					printaddr(data);
+					return RVAL_DECODED;
+				}
+
+				tprintf("{filter_off=%" PRIu64, filter_off);
+				return 0;
+			}
+
+			printaddr(data);
+			break;
 #ifndef IA64
 		case PTRACE_PEEKDATA:
 		case PTRACE_PEEKTEXT:
@@ -253,6 +269,32 @@ SYS_FUNC(ptrace)
 		case PTRACE_SECCOMP_GET_FILTER:
 			print_seccomp_fprog(tcp, data, tcp->u_rval);
 			break;
+		case PTRACE_SECCOMP_GET_METADATA: {
+			const size_t offset = sizeof(uint64_t);
+			uint64_t flags = 0;
+			size_t ret_size = MIN((kernel_ulong_t) tcp->u_rval,
+					      offset + sizeof(flags));
+
+			if (syserror(tcp) || ret_size <= offset) {
+				tprints("}");
+				return 0;
+			}
+
+			if (umoven(tcp, data + offset, ret_size - offset,
+				   &flags)) {
+				tprints(", ...}");
+				return 0;
+			}
+
+			tprints(", flags=");
+			printflags64(seccomp_filter_flags, flags,
+				     "SECCOMP_FILTER_FLAG_???");
+
+			if ((kernel_ulong_t) tcp->u_rval > ret_size)
+				tprints(", ...");
+
+			tprints("}");
+		}
 		}
 	}
 	return 0;

ptrace.h

@@ -171,6 +171,9 @@
 #ifndef PTRACE_SECCOMP_GET_FILTER
 # define PTRACE_SECCOMP_GET_FILTER	0x420c
 #endif
+#ifndef PTRACE_SECCOMP_GET_METADATA
+# define PTRACE_SECCOMP_GET_METADATA	0x420d
+#endif
 
 #if !HAVE_DECL_PTRACE_PEEKUSER
 # define PTRACE_PEEKUSER PTRACE_PEEKUSR

tests/ptrace.c

@@ -33,7 +33,9 @@
 
 #include <errno.h>
 #include "ptrace.h"
+#include <inttypes.h>
 #include <signal.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/wait.h>
@@ -177,6 +179,8 @@ main(void)
 	const unsigned long pid =
 		(unsigned long) 0xdefaced00000000ULL | (unsigned) getpid();
 
+	uint64_t *filter_off = tail_alloc(sizeof(*filter_off));
+
 	const unsigned int sigset_size = get_sigset_size();
 
 	void *const k_set = tail_alloc(sigset_size);
@@ -246,6 +250,22 @@ main(void)
 	printf("ptrace(PTRACE_SECCOMP_GET_FILTER, %u, 42, NULL) = %s\n",
 	       (unsigned) pid, errstr);
 
+	do_ptrace(PTRACE_SECCOMP_GET_METADATA, pid, bad_data, 0);
+	printf("ptrace(PTRACE_SECCOMP_GET_METADATA, %u, %lu, NULL) = %s\n",
+	       (unsigned) pid, bad_data, errstr);
+
+	do_ptrace(PTRACE_SECCOMP_GET_METADATA, pid, 7,
+		  (unsigned long) filter_off);
+	printf("ptrace(PTRACE_SECCOMP_GET_METADATA, %u, 7, %p) = %s\n",
+	       (unsigned) pid, filter_off, errstr);
+
+	*filter_off = 0xfacefeeddeadc0deULL;
+	do_ptrace(PTRACE_SECCOMP_GET_METADATA, pid, bad_data,
+		  (unsigned long) filter_off);
+	printf("ptrace(PTRACE_SECCOMP_GET_METADATA, %u, %lu, "
+	       "{filter_off=%" PRIu64 "}) = %s\n",
+	       (unsigned) pid, bad_data, *filter_off, errstr);
+
 	do_ptrace(PTRACE_GETEVENTMSG, pid, bad_request, bad_data);
 	printf("ptrace(PTRACE_GETEVENTMSG, %u, %#lx, %#lx) = %s\n",
 	       (unsigned) pid, bad_request, bad_data, errstr);

xlat/ptrace_cmds.in

@@ -33,6 +33,7 @@ PTRACE_PEEKSIGINFO
 PTRACE_GETSIGMASK
 PTRACE_SETSIGMASK
 PTRACE_SECCOMP_GET_FILTER
+PTRACE_SECCOMP_GET_METADATA
 /* arch-specific */
 PTRACE_GET_THREAD_AREA
 PTRACE_SET_THREAD_AREA