Format FDs in strace logs

Normal files display their path in the current mount namespace:

I0410 10:57:54.964196  216336 x:0] [   1] ls X read(0x3 /proc/filesystems, 0x55cee3bdb2c0 "nodev\t9p\nnodev\tdevpts \nnodev\tdevtmpfs\nnodev\tproc\nnodev\tramdiskfs\nnodev\tsysfs\nnodev\ttmpfs\n", 0x1000) = 0x58 (24.462?s)

AT_FDCWD includes the CWD:

I0411 12:58:48.278427    1526 x:0] [   1] stat_test E newfstatat(AT_FDCWD /home/prattmic, 0x55ea719b564e /proc/self, 0x7ef5cefc2be8, 0x0)

Sockets (and other non-vfs files) display an inode number (like
/proc/PID/fd):

I0410 10:54:38.909123  207684 x:0] [   1] nc E bind(0x3 socket:[1], 0x55b5a1652040 {Family: AF_INET, Addr: , Port: 8080}, 0x10)

I also fixed a few syscall args that should be Path.

PiperOrigin-RevId: 243169025
Change-Id: Ic7dda6a82ae27062fe2a4a371557acfd6a21fa2a

4 files changed, 112 insertions, 76 deletions

diff --git a/pkg/sentry/strace/BUILD b/pkg/sentry/strace/BUILD
index 73f1e9814..bcd94b42e 100644
--- a/pkg/sentry/strace/BUILD
+++ b/pkg/sentry/strace/BUILD
@@ -29,6 +29,7 @@ go_library(
         "//pkg/seccomp",
         "//pkg/sentry/arch",
         "//pkg/sentry/kernel",
+        "//pkg/sentry/kernel/kdefs",
         "//pkg/sentry/socket/control",
         "//pkg/sentry/socket/epsocket",
         "//pkg/sentry/socket/netlink",
diff --git a/pkg/sentry/strace/linux64.go b/pkg/sentry/strace/linux64.go
index ca695e80f..22b76449c 100644
--- a/pkg/sentry/strace/linux64.go
+++ b/pkg/sentry/strace/linux64.go
@@ -17,27 +17,27 @@ package strace
 // linuxAMD64 provides a mapping of the Linux amd64 syscalls and their argument
 // types for display / formatting.
 var linuxAMD64 = SyscallMap{
-	0:   makeSyscallInfo("read", Hex, ReadBuffer, Hex),
-	1:   makeSyscallInfo("write", Hex, WriteBuffer, Hex),
+	0:   makeSyscallInfo("read", FD, ReadBuffer, Hex),
+	1:   makeSyscallInfo("write", FD, WriteBuffer, Hex),
 	2:   makeSyscallInfo("open", Path, OpenFlags, Mode),
-	3:   makeSyscallInfo("close", Hex),
+	3:   makeSyscallInfo("close", FD),
 	4:   makeSyscallInfo("stat", Path, Stat),
-	5:   makeSyscallInfo("fstat", Hex, Stat),
+	5:   makeSyscallInfo("fstat", FD, Stat),
 	6:   makeSyscallInfo("lstat", Path, Stat),
 	7:   makeSyscallInfo("poll", Hex, Hex, Hex),
 	8:   makeSyscallInfo("lseek", Hex, Hex, Hex),
-	9:   makeSyscallInfo("mmap", Hex, Hex, Hex, Hex, Hex, Hex),
+	9:   makeSyscallInfo("mmap", Hex, Hex, Hex, Hex, FD, Hex),
 	10:  makeSyscallInfo("mprotect", Hex, Hex, Hex),
 	11:  makeSyscallInfo("munmap", Hex, Hex),
 	12:  makeSyscallInfo("brk", Hex),
 	13:  makeSyscallInfo("rt_sigaction", Signal, SigAction, PostSigAction),
 	14:  makeSyscallInfo("rt_sigprocmask", SignalMaskAction, SigSet, PostSigSet, Hex),
 	15:  makeSyscallInfo("rt_sigreturn"),
-	16:  makeSyscallInfo("ioctl", Hex, Hex, Hex),
-	17:  makeSyscallInfo("pread64", Hex, ReadBuffer, Hex, Hex),
-	18:  makeSyscallInfo("pwrite64", Hex, WriteBuffer, Hex, Hex),
-	19:  makeSyscallInfo("readv", Hex, ReadIOVec, Hex),
-	20:  makeSyscallInfo("writev", Hex, WriteIOVec, Hex),
+	16:  makeSyscallInfo("ioctl", FD, Hex, Hex),
+	17:  makeSyscallInfo("pread64", FD, ReadBuffer, Hex, Hex),
+	18:  makeSyscallInfo("pwrite64", FD, WriteBuffer, Hex, Hex),
+	19:  makeSyscallInfo("readv", FD, ReadIOVec, Hex),
+	20:  makeSyscallInfo("writev", FD, WriteIOVec, Hex),
 	21:  makeSyscallInfo("access", Path, Oct),
 	22:  makeSyscallInfo("pipe", PipeFDs),
 	23:  makeSyscallInfo("select", Hex, Hex, Hex, Hex, Timeval),
@@ -49,30 +49,30 @@ var linuxAMD64 = SyscallMap{
 	29:  makeSyscallInfo("shmget", Hex, Hex, Hex),
 	30:  makeSyscallInfo("shmat", Hex, Hex, Hex),
 	31:  makeSyscallInfo("shmctl", Hex, Hex, Hex),
-	32:  makeSyscallInfo("dup", Hex),
-	33:  makeSyscallInfo("dup2", Hex, Hex),
+	32:  makeSyscallInfo("dup", FD),
+	33:  makeSyscallInfo("dup2", FD, FD),
 	34:  makeSyscallInfo("pause"),
 	35:  makeSyscallInfo("nanosleep", Timespec, PostTimespec),
 	36:  makeSyscallInfo("getitimer", ItimerType, PostItimerVal),
 	37:  makeSyscallInfo("alarm", Hex),
 	38:  makeSyscallInfo("setitimer", ItimerType, ItimerVal, PostItimerVal),
 	39:  makeSyscallInfo("getpid"),
-	40:  makeSyscallInfo("sendfile", Hex, Hex, Hex, Hex),
+	40:  makeSyscallInfo("sendfile", FD, FD, Hex, Hex),
 	41:  makeSyscallInfo("socket", SockFamily, SockType, SockProtocol),
-	42:  makeSyscallInfo("connect", Hex, SockAddr, Hex),
-	43:  makeSyscallInfo("accept", Hex, PostSockAddr, SockLen),
-	44:  makeSyscallInfo("sendto", Hex, Hex, Hex, Hex, SockAddr, Hex),
-	45:  makeSyscallInfo("recvfrom", Hex, Hex, Hex, Hex, PostSockAddr, SockLen),
-	46:  makeSyscallInfo("sendmsg", Hex, SendMsgHdr, Hex),
-	47:  makeSyscallInfo("recvmsg", Hex, RecvMsgHdr, Hex),
-	48:  makeSyscallInfo("shutdown", Hex, Hex),
-	49:  makeSyscallInfo("bind", Hex, SockAddr, Hex),
-	50:  makeSyscallInfo("listen", Hex, Hex),
-	51:  makeSyscallInfo("getsockname", Hex, PostSockAddr, SockLen),
-	52:  makeSyscallInfo("getpeername", Hex, PostSockAddr, SockLen),
+	42:  makeSyscallInfo("connect", FD, SockAddr, Hex),
+	43:  makeSyscallInfo("accept", FD, PostSockAddr, SockLen),
+	44:  makeSyscallInfo("sendto", FD, Hex, Hex, Hex, SockAddr, Hex),
+	45:  makeSyscallInfo("recvfrom", FD, Hex, Hex, Hex, PostSockAddr, SockLen),
+	46:  makeSyscallInfo("sendmsg", FD, SendMsgHdr, Hex),
+	47:  makeSyscallInfo("recvmsg", FD, RecvMsgHdr, Hex),
+	48:  makeSyscallInfo("shutdown", FD, Hex),
+	49:  makeSyscallInfo("bind", FD, SockAddr, Hex),
+	50:  makeSyscallInfo("listen", FD, Hex),
+	51:  makeSyscallInfo("getsockname", FD, PostSockAddr, SockLen),
+	52:  makeSyscallInfo("getpeername", FD, PostSockAddr, SockLen),
 	53:  makeSyscallInfo("socketpair", SockFamily, SockType, SockProtocol, Hex),
-	54:  makeSyscallInfo("setsockopt", Hex, Hex, Hex, Hex, Hex),
-	55:  makeSyscallInfo("getsockopt", Hex, Hex, Hex, Hex, Hex),
+	54:  makeSyscallInfo("setsockopt", FD, Hex, Hex, Hex, Hex),
+	55:  makeSyscallInfo("getsockopt", FD, Hex, Hex, Hex, Hex),
 	56:  makeSyscallInfo("clone", CloneFlags, Hex, Hex, Hex, Hex),
 	57:  makeSyscallInfo("fork"),
 	58:  makeSyscallInfo("vfork"),
@@ -89,16 +89,16 @@ var linuxAMD64 = SyscallMap{
 	69:  makeSyscallInfo("msgsnd", Hex, Hex, Hex, Hex),
 	70:  makeSyscallInfo("msgrcv", Hex, Hex, Hex, Hex, Hex),
 	71:  makeSyscallInfo("msgctl", Hex, Hex, Hex),
-	72:  makeSyscallInfo("fcntl", Hex, Hex, Hex),
-	73:  makeSyscallInfo("flock", Hex, Hex),
-	74:  makeSyscallInfo("fsync", Hex),
-	75:  makeSyscallInfo("fdatasync", Hex),
+	72:  makeSyscallInfo("fcntl", FD, Hex, Hex),
+	73:  makeSyscallInfo("flock", FD, Hex),
+	74:  makeSyscallInfo("fsync", FD),
+	75:  makeSyscallInfo("fdatasync", FD),
 	76:  makeSyscallInfo("truncate", Path, Hex),
-	77:  makeSyscallInfo("ftruncate", Hex, Hex),
-	78:  makeSyscallInfo("getdents", Hex, Hex, Hex),
+	77:  makeSyscallInfo("ftruncate", FD, Hex),
+	78:  makeSyscallInfo("getdents", FD, Hex, Hex),
 	79:  makeSyscallInfo("getcwd", PostPath, Hex),
 	80:  makeSyscallInfo("chdir", Path),
-	81:  makeSyscallInfo("fchdir", Hex),
+	81:  makeSyscallInfo("fchdir", FD),
 	82:  makeSyscallInfo("rename", Path, Path),
 	83:  makeSyscallInfo("mkdir", Path, Oct),
 	84:  makeSyscallInfo("rmdir", Path),
@@ -108,10 +108,10 @@ var linuxAMD64 = SyscallMap{
 	88:  makeSyscallInfo("symlink", Path, Path),
 	89:  makeSyscallInfo("readlink", Path, ReadBuffer, Hex),
 	90:  makeSyscallInfo("chmod", Path, Mode),
-	91:  makeSyscallInfo("fchmod", Hex, Mode),
+	91:  makeSyscallInfo("fchmod", FD, Mode),
 	92:  makeSyscallInfo("chown", Path, Hex, Hex),
-	93:  makeSyscallInfo("fchown", Hex, Hex, Hex),
-	94:  makeSyscallInfo("lchown", Hex, Hex, Hex),
+	93:  makeSyscallInfo("fchown", FD, Hex, Hex),
+	94:  makeSyscallInfo("lchown", Path, Hex, Hex),
 	95:  makeSyscallInfo("umask", Hex),
 	96:  makeSyscallInfo("gettimeofday", Timeval, Hex),
 	97:  makeSyscallInfo("getrlimit", Hex, Hex),
@@ -155,7 +155,7 @@ var linuxAMD64 = SyscallMap{
 	135: makeSyscallInfo("personality", Hex),
 	136: makeSyscallInfo("ustat", Hex, Hex),
 	137: makeSyscallInfo("statfs", Path, Hex),
-	138: makeSyscallInfo("fstatfs", Hex, Hex),
+	138: makeSyscallInfo("fstatfs", FD, Hex),
 	139: makeSyscallInfo("sysfs", Hex, Hex, Hex),
 	140: makeSyscallInfo("getpriority", Hex, Hex),
 	141: makeSyscallInfo("setpriority", Hex, Hex, Hex),
@@ -172,7 +172,7 @@ var linuxAMD64 = SyscallMap{
 	152: makeSyscallInfo("munlockall"),
 	153: makeSyscallInfo("vhangup"),
 	154: makeSyscallInfo("modify_ldt", Hex, Hex, Hex),
-	155: makeSyscallInfo("pivot_root", Hex, Hex),
+	155: makeSyscallInfo("pivot_root", Path, Path),
 	156: makeSyscallInfo("_sysctl", Hex),
 	157: makeSyscallInfo("prctl", Hex, Hex, Hex, Hex, Hex),
 	158: makeSyscallInfo("arch_prctl", Hex, Hex),
@@ -207,16 +207,16 @@ var linuxAMD64 = SyscallMap{
 	187: makeSyscallInfo("readahead", Hex, Hex, Hex),
 	188: makeSyscallInfo("setxattr", Path, Path, Hex, Hex, Hex),
 	189: makeSyscallInfo("lsetxattr", Path, Path, Hex, Hex, Hex),
-	190: makeSyscallInfo("fsetxattr", Hex, Path, Hex, Hex, Hex),
+	190: makeSyscallInfo("fsetxattr", FD, Path, Hex, Hex, Hex),
 	191: makeSyscallInfo("getxattr", Path, Path, Hex, Hex),
 	192: makeSyscallInfo("lgetxattr", Path, Path, Hex, Hex),
-	193: makeSyscallInfo("fgetxattr", Hex, Path, Hex, Hex),
+	193: makeSyscallInfo("fgetxattr", FD, Path, Hex, Hex),
 	194: makeSyscallInfo("listxattr", Path, Path, Hex),
 	195: makeSyscallInfo("llistxattr", Path, Path, Hex),
-	196: makeSyscallInfo("flistxattr", Hex, Path, Hex),
+	196: makeSyscallInfo("flistxattr", FD, Path, Hex),
 	197: makeSyscallInfo("removexattr", Path, Path),
 	198: makeSyscallInfo("lremovexattr", Path, Path),
-	199: makeSyscallInfo("fremovexattr", Hex, Path),
+	199: makeSyscallInfo("fremovexattr", FD, Path),
 	200: makeSyscallInfo("tkill", Hex, Signal),
 	201: makeSyscallInfo("time", Hex),
 	202: makeSyscallInfo("futex", Hex, FutexOp, Hex, Timespec, Hex, Hex),
@@ -234,11 +234,11 @@ var linuxAMD64 = SyscallMap{
 	// 214: epoll_ctl_old (not implemented in the Linux kernel)
 	// 215: epoll_wait_old (not implemented in the Linux kernel)
 	216: makeSyscallInfo("remap_file_pages", Hex, Hex, Hex, Hex, Hex),
-	217: makeSyscallInfo("getdents64", Hex, Hex, Hex),
+	217: makeSyscallInfo("getdents64", FD, Hex, Hex),
 	218: makeSyscallInfo("set_tid_address", Hex),
 	219: makeSyscallInfo("restart_syscall"),
 	220: makeSyscallInfo("semtimedop", Hex, Hex, Hex, Hex),
-	221: makeSyscallInfo("fadvise64", Hex, Hex, Hex, Hex),
+	221: makeSyscallInfo("fadvise64", FD, Hex, Hex, Hex),
 	222: makeSyscallInfo("timer_create", Hex, Hex, Hex),
 	223: makeSyscallInfo("timer_settime", Hex, Hex, ItimerSpec, PostItimerSpec),
 	224: makeSyscallInfo("timer_gettime", Hex, PostItimerSpec),
@@ -250,7 +250,7 @@ var linuxAMD64 = SyscallMap{
 	230: makeSyscallInfo("clock_nanosleep", Hex, Hex, Timespec, PostTimespec),
 	231: makeSyscallInfo("exit_group", Hex),
 	232: makeSyscallInfo("epoll_wait", Hex, Hex, Hex, Hex),
-	233: makeSyscallInfo("epoll_ctl", Hex, Hex, Hex, Hex),
+	233: makeSyscallInfo("epoll_ctl", Hex, Hex, FD, Hex),
 	234: makeSyscallInfo("tgkill", Hex, Hex, Signal),
 	235: makeSyscallInfo("utimes", Path, Timeval),
 	// 236: vserver (not implemented in the Linux kernel)
@@ -274,58 +274,58 @@ var linuxAMD64 = SyscallMap{
 	254: makeSyscallInfo("inotify_add_watch", Hex, Path, Hex),
 	255: makeSyscallInfo("inotify_rm_watch", Hex, Hex),
 	256: makeSyscallInfo("migrate_pages", Hex, Hex, Hex, Hex),
-	257: makeSyscallInfo("openat", Hex, Path, OpenFlags, Mode),
-	258: makeSyscallInfo("mkdirat", Hex, Path, Hex),
-	259: makeSyscallInfo("mknodat", Hex, Path, Mode, Hex),
-	260: makeSyscallInfo("fchownat", Hex, Path, Hex, Hex, Hex),
-	261: makeSyscallInfo("futimesat", Hex, Path, Hex),
-	262: makeSyscallInfo("newfstatat", Hex, Path, Stat, Hex),
-	263: makeSyscallInfo("unlinkat", Hex, Path, Hex),
-	264: makeSyscallInfo("renameat", Hex, Path, Hex, Path),
-	265: makeSyscallInfo("linkat", Hex, Path, Hex, Path, Hex),
+	257: makeSyscallInfo("openat", FD, Path, OpenFlags, Mode),
+	258: makeSyscallInfo("mkdirat", FD, Path, Hex),
+	259: makeSyscallInfo("mknodat", FD, Path, Mode, Hex),
+	260: makeSyscallInfo("fchownat", FD, Path, Hex, Hex, Hex),
+	261: makeSyscallInfo("futimesat", FD, Path, Hex),
+	262: makeSyscallInfo("newfstatat", FD, Path, Stat, Hex),
+	263: makeSyscallInfo("unlinkat", FD, Path, Hex),
+	264: makeSyscallInfo("renameat", FD, Path, Hex, Path),
+	265: makeSyscallInfo("linkat", FD, Path, Hex, Path, Hex),
 	266: makeSyscallInfo("symlinkat", Path, Hex, Path),
-	267: makeSyscallInfo("readlinkat", Hex, Path, ReadBuffer, Hex),
-	268: makeSyscallInfo("fchmodat", Hex, Path, Mode),
-	269: makeSyscallInfo("faccessat", Hex, Path, Oct, Hex),
+	267: makeSyscallInfo("readlinkat", FD, Path, ReadBuffer, Hex),
+	268: makeSyscallInfo("fchmodat", FD, Path, Mode),
+	269: makeSyscallInfo("faccessat", FD, Path, Oct, Hex),
 	270: makeSyscallInfo("pselect6", Hex, Hex, Hex, Hex, Hex, Hex),
 	271: makeSyscallInfo("ppoll", Hex, Hex, Timespec, SigSet, Hex),
 	272: makeSyscallInfo("unshare", CloneFlags),
 	273: makeSyscallInfo("set_robust_list", Hex, Hex),
 	274: makeSyscallInfo("get_robust_list", Hex, Hex, Hex),
-	275: makeSyscallInfo("splice", Hex, Hex, Hex, Hex, Hex, Hex),
-	276: makeSyscallInfo("tee", Hex, Hex, Hex, Hex),
-	277: makeSyscallInfo("sync_file_range", Hex, Hex, Hex, Hex),
-	278: makeSyscallInfo("vmsplice", Hex, Hex, Hex, Hex),
+	275: makeSyscallInfo("splice", FD, Hex, FD, Hex, Hex, Hex),
+	276: makeSyscallInfo("tee", FD, FD, Hex, Hex),
+	277: makeSyscallInfo("sync_file_range", FD, Hex, Hex, Hex),
+	278: makeSyscallInfo("vmsplice", FD, Hex, Hex, Hex),
 	279: makeSyscallInfo("move_pages", Hex, Hex, Hex, Hex, Hex, Hex),
-	280: makeSyscallInfo("utimensat", Hex, Path, UTimeTimespec, Hex),
+	280: makeSyscallInfo("utimensat", FD, Path, UTimeTimespec, Hex),
 	281: makeSyscallInfo("epoll_pwait", Hex, Hex, Hex, Hex, SigSet, Hex),
 	282: makeSyscallInfo("signalfd", Hex, Hex, Hex),
 	283: makeSyscallInfo("timerfd_create", Hex, Hex),
 	284: makeSyscallInfo("eventfd", Hex),
-	285: makeSyscallInfo("fallocate", Hex, Hex, Hex, Hex),
-	286: makeSyscallInfo("timerfd_settime", Hex, Hex, ItimerSpec, PostItimerSpec),
-	287: makeSyscallInfo("timerfd_gettime", Hex, PostItimerSpec),
-	288: makeSyscallInfo("accept4", Hex, PostSockAddr, SockLen, SockFlags),
+	285: makeSyscallInfo("fallocate", FD, Hex, Hex, Hex),
+	286: makeSyscallInfo("timerfd_settime", FD, Hex, ItimerSpec, PostItimerSpec),
+	287: makeSyscallInfo("timerfd_gettime", FD, PostItimerSpec),
+	288: makeSyscallInfo("accept4", FD, PostSockAddr, SockLen, SockFlags),
 	289: makeSyscallInfo("signalfd4", Hex, Hex, Hex, Hex),
 	290: makeSyscallInfo("eventfd2", Hex, Hex),
 	291: makeSyscallInfo("epoll_create1", Hex),
-	292: makeSyscallInfo("dup3", Hex, Hex, Hex),
+	292: makeSyscallInfo("dup3", FD, FD, Hex),
 	293: makeSyscallInfo("pipe2", PipeFDs, Hex),
 	294: makeSyscallInfo("inotify_init1", Hex),
-	295: makeSyscallInfo("preadv", Hex, ReadIOVec, Hex, Hex),
-	296: makeSyscallInfo("pwritev", Hex, WriteIOVec, Hex, Hex),
+	295: makeSyscallInfo("preadv", FD, ReadIOVec, Hex, Hex),
+	296: makeSyscallInfo("pwritev", FD, WriteIOVec, Hex, Hex),
 	297: makeSyscallInfo("rt_tgsigqueueinfo", Hex, Hex, Signal, Hex),
 	298: makeSyscallInfo("perf_event_open", Hex, Hex, Hex, Hex, Hex),
-	299: makeSyscallInfo("recvmmsg", Hex, Hex, Hex, Hex, Hex),
+	299: makeSyscallInfo("recvmmsg", FD, Hex, Hex, Hex, Hex),
 	300: makeSyscallInfo("fanotify_init", Hex, Hex),
 	301: makeSyscallInfo("fanotify_mark", Hex, Hex, Hex, Hex, Hex),
 	302: makeSyscallInfo("prlimit64", Hex, Hex, Hex, Hex),
-	303: makeSyscallInfo("name_to_handle_at", Hex, Hex, Hex, Hex, Hex),
-	304: makeSyscallInfo("open_by_handle_at", Hex, Hex, Hex),
+	303: makeSyscallInfo("name_to_handle_at", FD, Hex, Hex, Hex, Hex),
+	304: makeSyscallInfo("open_by_handle_at", FD, Hex, Hex),
 	305: makeSyscallInfo("clock_adjtime", Hex, Hex),
-	306: makeSyscallInfo("syncfs", Hex),
-	307: makeSyscallInfo("sendmmsg", Hex, Hex, Hex, Hex),
-	308: makeSyscallInfo("setns", Hex, Hex),
+	306: makeSyscallInfo("syncfs", FD),
+	307: makeSyscallInfo("sendmmsg", FD, Hex, Hex, Hex),
+	308: makeSyscallInfo("setns", FD, Hex),
 	309: makeSyscallInfo("getcpu", Hex, Hex, Hex),
 	310: makeSyscallInfo("process_vm_readv", Hex, ReadIOVec, Hex, IOVec, Hex, Hex),
 	311: makeSyscallInfo("process_vm_writev", Hex, IOVec, Hex, WriteIOVec, Hex, Hex),
@@ -333,6 +333,6 @@ var linuxAMD64 = SyscallMap{
 	313: makeSyscallInfo("finit_module", Hex, Hex, Hex),
 	314: makeSyscallInfo("sched_setattr", Hex, Hex, Hex),
 	315: makeSyscallInfo("sched_getattr", Hex, Hex, Hex),
-	316: makeSyscallInfo("renameat2", Hex, Path, Hex, Path, Hex),
+	316: makeSyscallInfo("renameat2", FD, Path, Hex, Path, Hex),
 	317: makeSyscallInfo("seccomp", Hex, Hex, Hex),
 }
diff --git a/pkg/sentry/strace/strace.go b/pkg/sentry/strace/strace.go
index a7e9df268..398035b65 100644
--- a/pkg/sentry/strace/strace.go
+++ b/pkg/sentry/strace/strace.go
@@ -31,6 +31,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/seccomp"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/kdefs"
 	pb "gvisor.googlesource.com/gvisor/pkg/sentry/strace/strace_go_proto"
 	slinux "gvisor.googlesource.com/gvisor/pkg/sentry/syscalls/linux"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
@@ -132,6 +133,35 @@ func path(t *kernel.Task, addr usermem.Addr) string {
 	return fmt.Sprintf("%#x %s", addr, path)
 }
 
+func fd(t *kernel.Task, fd kdefs.FD) string {
+	root := t.FSContext().RootDirectory()
+	if root != nil {
+		defer root.DecRef()
+	}
+
+	if fd == linux.AT_FDCWD {
+		wd := t.FSContext().WorkingDirectory()
+		var name string
+		if wd != nil {
+			defer wd.DecRef()
+			name, _ = wd.FullName(root)
+		} else {
+			name = "(unknown cwd)"
+		}
+		return fmt.Sprintf("AT_FDCWD %s", name)
+	}
+
+	file := t.FDMap().GetFile(fd)
+	if file == nil {
+		// Cast FD to uint64 to avoid printing negative hex.
+		return fmt.Sprintf("%#x (bad FD)", uint64(fd))
+	}
+	defer file.DecRef()
+
+	name, _ := file.Dirent.FullName(root)
+	return fmt.Sprintf("%#x %s", fd, name)
+}
+
 func fdpair(t *kernel.Task, addr usermem.Addr) string {
 	var fds [2]int32
 	_, err := t.CopyIn(addr, &fds)
@@ -344,6 +374,8 @@ func (i *SyscallInfo) pre(t *kernel.Task, args arch.SyscallArguments, maximumBlo
 			break
 		}
 		switch i.format[arg] {
+		case FD:
+			output = append(output, fd(t, kdefs.FD(args[arg].Int())))
 		case WriteBuffer:
 			output = append(output, dump(t, args[arg].Pointer(), args[arg+1].SizeT(), maximumBlobSize))
 		case WriteIOVec:
diff --git a/pkg/sentry/strace/syscalls.go b/pkg/sentry/strace/syscalls.go
index b2715856e..1f255c717 100644
--- a/pkg/sentry/strace/syscalls.go
+++ b/pkg/sentry/strace/syscalls.go
@@ -35,6 +35,9 @@ const (
 	// Oct is just an octal number.
 	Oct
 
+	// FD is a file descriptor.
+	FD
+
 	// ReadBuffer is a buffer for a read-style call. The syscall return
 	// value is used for the length.
 	//