proc: show file flags in fdinfo

Currently, there is an attempt to print FD flags, but
they are not decoded into a number, so we see something like this:

/criu # cat /proc/self/fdinfo/0
flags: {%!o(bool=000false)}

Actually, fdinfo has to contain file flags.

Change-Id: Idcbb7db908067447eb9ae6f2c3cfb861f2be1a97
PiperOrigin-RevId: 206794498

1 files changed, 39 insertions, 0 deletions

diff --git a/pkg/sentry/fs/flags.go b/pkg/sentry/fs/flags.go
index 810452584..da0ff58af 100644
--- a/pkg/sentry/fs/flags.go
+++ b/pkg/sentry/fs/flags.go
@@ -14,6 +14,10 @@
 
 package fs
 
+import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+)
+
 // FileFlags encodes file flags.
 type FileFlags struct {
 	// Direct indicates that I/O should be done directly.
@@ -78,3 +82,38 @@ func (f FileFlags) Settable() SettableFileFlags {
 		Async:       f.Async,
 	}
 }
+
+// ToLinux converts a FileFlags object to a Linux representation.
+func (f FileFlags) ToLinux() (mask uint) {
+	if f.Direct {
+		mask |= linux.O_DIRECT
+	}
+	if f.NonBlocking {
+		mask |= linux.O_NONBLOCK
+	}
+	if f.Sync {
+		mask |= linux.O_SYNC
+	}
+	if f.Append {
+		mask |= linux.O_APPEND
+	}
+	if f.Directory {
+		mask |= linux.O_DIRECTORY
+	}
+	if f.Async {
+		mask |= linux.O_ASYNC
+	}
+	if f.LargeFile {
+		mask |= linux.O_LARGEFILE
+	}
+
+	switch {
+	case f.Read && f.Write:
+		mask |= linux.O_RDWR
+	case f.Write:
+		mask |= linux.O_WRONLY
+	case f.Read:
+		mask |= linux.O_RDONLY
+	}
+	return
+}