Introduce two new helper functions to deal with stdio redirecation in a
uniform, reliable manner:
The patch_fd() function will attempt to redirect the given fd number to the
specified file, using the supplied flags for the open() syscall. When the
device is NULL, "/dev/null" is asumed, when the device is a relative path,
openat() is used to open it relative to the "/dev" directory. When the device
cannot be openend, a fallback to "/dev/null" is attempted.
The patch_stdio() function is essentially a wrapper around patch_fd(),
providing an easy interface to redirect stdin, stdout and stderr to the same
given device.
Both function return 0 on success and -1 on error. The errno variable will
be set accordingly.
Signed-off-by: Jo-Philipp Wich <j...@mein.io>
---
utils/utils.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
utils/utils.h | 3 +++
2 files changed, 57 insertions(+)
diff --git a/utils/utils.c b/utils/utils.c
index a67c004..ebf5447 100644
--- a/utils/utils.c
+++ b/utils/utils.c
@@ -20,6 +20,10 @@
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
+#include <string.h>
+#include <errno.h>
+
+#include "../log.h"
void
__blobmsg_list_init(struct blobmsg_list *list, int offset, int len,
blobmsg_list_cmp cmp)
@@ -152,3 +156,53 @@ char* get_cmdline_val(const char* name, char* out, int len)
return NULL;
}
+
+int patch_fd(const char *device, int fd, int flags)
+{
+ int dfd, nfd;
+
+ if (device == NULL)
+ device = "/dev/null";
+
+ if (*device != '/') {
+ dfd = open("/dev", O_RDONLY);
+
+ if (dfd < 0)
+ return -1;
+
+ nfd = openat(dfd, device, flags);
+
+ close(dfd);
+ } else {
+ nfd = open(device, flags);
+ }
+
+ if (nfd < 0 && strcmp(device, "/dev/null"))
+ nfd = open("/dev/null", flags);
+
+ if (nfd < 0)
+ return -1;
+
+ fd = dup2(nfd, fd);
+
+ if (nfd > STDERR_FILENO)
+ close(nfd);
+
+ return (fd < 0) ? -1 : 0;
+}
+
+int patch_stdio(const char *device)
+{
+ int fd, rv = 0;
+ const char *fdname[3] = { "stdin", "stdout", "stderr" };
+
+ for (fd = STDIN_FILENO; fd <= STDERR_FILENO; fd++) {
+ if (patch_fd(device, fd, fd ? O_WRONLY : O_RDONLY)) {
+ ERROR("Failed to redirect %s to %s: %d (%s)\n",
+ fdname[fd], device, errno, strerror(errno));
+ rv = -1;
+ }
+ }
+
+ return rv;
+}
diff --git a/utils/utils.h b/utils/utils.h
index 8b384fc..908c314 100644
--- a/utils/utils.h
+++ b/utils/utils.h
@@ -53,4 +53,7 @@ bool blobmsg_list_equal(struct blobmsg_list *l1, struct
blobmsg_list *l2);
void blobmsg_list_move(struct blobmsg_list *list, struct blobmsg_list *src);
char* get_cmdline_val(const char* name, char* out, int len);
+int patch_fd(const char *device, int fd, int flags);
+int patch_stdio(const char *device);
+
#endif
--
2.1.4
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