From dee3c3e7ba434c9890c5d3abea5908d76fba5e66 Mon Sep 17 00:00:00 2001
From: topjohnwu <topjohnwu@gmail.com>
Date: Sat, 2 Mar 2019 05:45:55 -0500
Subject: [PATCH] Workaround seccomp on MagiskBoot

Close #1150
---
 native/jni/utils/file.cpp | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/native/jni/utils/file.cpp b/native/jni/utils/file.cpp
index 236db143d..abd5a1de3 100644
--- a/native/jni/utils/file.cpp
+++ b/native/jni/utils/file.cpp
@@ -358,9 +358,13 @@ void full_read_at(int dirfd, const char *filename, void **buf, size_t *size) {
 }
 
 void write_zero(int fd, size_t size) {
-	size_t pos = lseek(fd, 0, SEEK_CUR);
-	ftruncate(fd, pos + size);
-	lseek(fd, pos + size, SEEK_SET);
+	char buf[4096] = {0};
+	size_t len;
+	while (size > 0) {
+		len = sizeof(buf) > size ? size : sizeof(buf);
+		write(fd, buf, len);
+		size -= len;
+	}
 }
 
 void file_readline(const char *filename, const function<bool (string_view&)> &fn, bool trim) {