gsctool: explicitly set buffering type to line buffered

This CL allows gsctool outputs to be instantly piped and shown in crosh
when crosh executes cr50-verify-ro.sh, which calls gsctool, indirectly
via debugd.

Program stdout buffering type by default changes from line buffered to
block buffered if the output is redirected to a file or pipe. Since we
are going to call gsctool from inside debugd (CL:1337190) and want to
pipe the output instantly to the dbus request sender, the buffering type
of gsctool needs to be explicitly set.

BRANCH=none
BUG=b:113893821
TEST=in crosh run verify_ro, which indirectly runs gsctool via debugd,
     and verify that output is instantly piped and shown in crosh.
     (see CL:1337190 for detailed output)

Signed-off-by: Wei-Cheng Xiao <garryxiao@chromium.org>
Change-Id: I515854a29e5e2ede0acc8c2d9e2c4df367a5062e
Reviewed-on: https://chromium-review.googlesource.com/1337250
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-by: Louis Collard <louiscollard@chromium.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/extra/usb_updater/gsctool.c b/extra/usb_updater/gsctool.c
index 31db8149ad..a3731528e6 100644
--- a/extra/usb_updater/gsctool.c
+++ b/extra/usb_updater/gsctool.c
@@ -2059,6 +2059,12 @@ int main(int argc, char *argv[])
 	char *factory_mode_arg;
 	char *tpm_mode_arg = NULL;
 
+	// Explicitly sets buffering type to line buffered so that output lines
+	// can be written to pipe instantly. This is needed when the
+	// cr50-verify-ro.sh execution in verify_ro is moved from crosh to
+	// debugd.
+	setlinebuf(stdout);
+
 	progname = strrchr(argv[0], '/');
 	if (progname)
 		progname++;