io_uring: implement decoding of IORING_REGISTER_PBUF_STATUS opcode

This io_uring_register opcode was introduced by Linux kernel commit
v6.8-rc1~29^2~8.

* src/io_uring.c (print_io_uring_buf_status): New function.
(SYS_FUNC(io_uring_register)): Use it to decode
IORING_REGISTER_PBUF_STATUS opcode.
* tests/io_uring_register.c (main): Check it.
* NEWS: Mention this change.

NEWS

@@ -5,8 +5,9 @@ Noteworthy changes in release ?.? (????-??-??)
   * Implemented --always-show-pid option.
   * The --user|-u option has learned to recognize numeric UID:GID pair, allowing
     e.g. statically-built strace to be used without invoking nss plugins.
-  * Implemented decoding of IORING_REGISTER_SYNC_CANCEL and
-    IORING_REGISTER_FILE_ALLOC_RANGE opcodes of io_uring_register syscall.
+  * Implemented decoding of IORING_REGISTER_SYNC_CANCEL,
+    IORING_REGISTER_FILE_ALLOC_RANGE, and IORING_REGISTER_PBUF_STATUS opcodes
+    of io_uring_register syscall.
   * Updated decoding of pidfd_send_signal syscall.
   * Updated lists of CAN_*, IORING_*, KEY_*, LSM_*, MPOL_*, NT_*, RWF_*,
     PIDFD_*, PTP_*, TCP_*, and *_MAGIC constants.

src/io_uring.c

@@ -672,6 +672,39 @@ print_io_uring_file_index_range(struct tcb *tcp, const kernel_ulong_t addr,
 	tprint_struct_end();
 }
 
+static int
+print_io_uring_buf_status(struct tcb *tcp, const kernel_ulong_t addr,
+			  const unsigned int nargs)
+{
+	struct io_uring_buf_status arg;
+
+	if (nargs != 1) {
+		printaddr(addr);
+		return RVAL_DECODED;
+	}
+
+	if (entering(tcp))
+		return 0;
+
+	if (umove_or_printaddr(tcp, addr, &arg))
+		return RVAL_DECODED;
+
+	tprint_struct_begin();
+	PRINT_FIELD_X(arg, buf_group);
+
+	tprint_struct_next();
+	PRINT_FIELD_X(arg, head);
+
+	if (!IS_ARRAY_ZERO(arg.resv)) {
+		tprint_struct_next();
+		PRINT_FIELD_ARRAY(arg, resv, tcp, print_xint_array_member);
+	}
+
+	tprint_struct_end();
+
+	return RVAL_DECODED;
+}
+
 SYS_FUNC(io_uring_register)
 {
 	const int fd = tcp->u_arg[0];
@@ -744,6 +777,9 @@ SYS_FUNC(io_uring_register)
 	case IORING_REGISTER_FILE_ALLOC_RANGE:
 		print_io_uring_file_index_range(tcp, arg, nargs);
 		break;
+	case IORING_REGISTER_PBUF_STATUS:
+		rc = print_io_uring_buf_status(tcp, arg, nargs);
+		break;
 	case IORING_UNREGISTER_BUFFERS:
 	case IORING_UNREGISTER_FILES:
 	case IORING_UNREGISTER_EVENTFD:

tests/io_uring_register.c

@@ -1290,6 +1290,73 @@ main(void)
 		}
 	}
 
+	/* IORING_REGISTER_PBUF_STATUS */
+	static const struct {
+		unsigned int op;
+		const char *str;
+	} buf_status_ops[] = {
+		{ 26, "IORING_REGISTER_PBUF_STATUS" },
+	};
+	TAIL_ALLOC_OBJECT_CONST_PTR(struct io_uring_buf_status, buf_status);
+
+	for (size_t i = 0; i < ARRAY_SIZE(buf_status_ops); i++) {
+		sys_io_uring_register(fd_null, buf_status_ops[i].op, 0,
+				      0xdeadbeef);
+		printf("io_uring_register(%u<%s>, " XLAT_FMT ", NULL, %u)"
+		       " = %s\n",
+		       fd_null, path_null,
+		       XLAT_SEL(buf_status_ops[i].op,
+			        buf_status_ops[i].str),
+		       0xdeadbeef, errstr);
+
+		sys_io_uring_register(fd_null, buf_status_ops[i].op,
+				      buf_status + 1, 0);
+		printf("io_uring_register(%u<%s>, " XLAT_FMT ", %p, 0) = %s\n",
+		       fd_null, path_null,
+		       XLAT_SEL(buf_status_ops[i].op, buf_status_ops[i].str),
+		       buf_status + 1, errstr);
+
+		for (size_t j = 0; j < (1U << 3); j++) {
+			memset(buf_status, 0, sizeof(*buf_status));
+			buf_status->buf_group = j & 1 ? 0xfacefeedU : 0;
+			buf_status->head = j & 2 ? 0xcafef00dU : 0;
+			buf_status->resv[7] = j & 4 ? 0xbadc0dedU : 0;
+
+			sys_io_uring_register(fd_null, buf_status_ops[i].op,
+					      buf_status, 0x42);
+			printf("io_uring_register(%u<%s>, " XLAT_FMT ", %p, 66)"
+			       " = %s\n",
+			       fd_null, path_null,
+			       XLAT_SEL(buf_status_ops[i].op,
+				        buf_status_ops[i].str),
+			       buf_status, errstr);
+
+			sys_io_uring_register(fd_null, buf_status_ops[i].op,
+					      buf_status, 1);
+			printf("io_uring_register(%u<%s>, " XLAT_FMT ", "
+#if RETVAL_INJECTED
+			       "{buf_group=%#x, head=%#x",
+#else
+			       "%p",
+#endif
+			       fd_null, path_null,
+			       XLAT_SEL(buf_status_ops[i].op,
+				        buf_status_ops[i].str),
+#if RETVAL_INJECTED
+			       buf_status->buf_group, buf_status->head
+#else
+			       buf_status
+#endif
+			       );
+#if RETVAL_INJECTED
+			if (j & 4)
+				printf(", resv=[0, 0, 0, 0, 0, 0, 0, 0xbadc0ded]");
+			printf("}");
+#endif
+			printf(", 1) = %s\n", errstr);
+		}
+	}
+
 	puts("+++ exited with 0 +++");
 	return 0;
 }