[Xen-devel] [PATCH 1/2] tools/helpers: Introduce cmp-fd-file-inode utility

[Jason Andryuk <jandryuk@xxxxxxxxx>]

This is a C implementation of the perl code inside of locking.sh to
check that the locked file descriptor and lock file share the same inode
and therefore match.  One change from the perl version is replacing
printing "y" on success with exit values of 0 (shell True) and 1 (shell
False).

Requiring perl is a large dependency for the single use, so a dedicated
utility removes that dependency for systems that otherwise would not
install perl.

Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx>
---
 .gitignore                        |  1 +
 tools/helpers/Makefile            |  3 +++
 tools/helpers/cmp-fd-file-inode.c | 43 +++++++++++++++++++++++++++++++
 3 files changed, 47 insertions(+)
 create mode 100644 tools/helpers/cmp-fd-file-inode.c

diff --git a/.gitignore b/.gitignore
index 4ca679ddbc..897f878eef 100644
--- a/.gitignore
+++ b/.gitignore
@@ -164,6 +164,7 @@ tools/fuzz/x86_instruction_emulator/x86-emulate.[ch]
 tools/helpers/_paths.h
 tools/helpers/init-xenstore-domain
 tools/helpers/xen-init-dom0
+tools/helpers/cmp-fd-file-inode
 tools/hotplug/common/hotplugpath.sh
 tools/hotplug/FreeBSD/rc.d/xencommons
 tools/hotplug/FreeBSD/rc.d/xendriverdomain
diff --git a/tools/helpers/Makefile b/tools/helpers/Makefile
index f759528322..7daf5c46ca 100644
--- a/tools/helpers/Makefile
+++ b/tools/helpers/Makefile
@@ -8,6 +8,7 @@ include $(XEN_ROOT)/tools/Rules.mk
 PROGS += xen-init-dom0
 ifeq ($(CONFIG_Linux),y)
 PROGS += init-xenstore-domain
+PROGS += cmp-fd-file-inode
 endif
 
 XEN_INIT_DOM0_OBJS = xen-init-dom0.o init-dom-json.o
@@ -40,12 +41,14 @@ install: all
        $(INSTALL_PROG) xen-init-dom0 $(DESTDIR)$(LIBEXEC_BIN)
 ifeq ($(CONFIG_Linux),y)
        $(INSTALL_PROG) init-xenstore-domain $(DESTDIR)$(LIBEXEC_BIN)
+       $(INSTALL_PROG) cmp-fd-file-inode $(DESTDIR)$(LIBEXEC_BIN)
 endif
 
 .PHONY: uninstall
 uninstall:
 ifeq ($(CONFIG_Linux),y)
        rm -f $(DESTDIR)$(LIBEXEC_BIN)/init-xenstore-domain
+       rm -f $(DESTDIR)$(LIBEXEC_BIN)/cmp-fd-file-inode
 endif
        rm -f $(DESTDIR)$(LIBEXEC_BIN)/xen-init-dom0
 
diff --git a/tools/helpers/cmp-fd-file-inode.c 
b/tools/helpers/cmp-fd-file-inode.c
new file mode 100644
index 0000000000..886ea888ed
--- /dev/null
+++ b/tools/helpers/cmp-fd-file-inode.c
@@ -0,0 +1,43 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+void usage(const char * prog)
+{
+    fprintf(stderr,
+"%s <fd> <filename>\n"
+"Checks that the open file descriptor (referenced by number) has the same\n"
+"inode as the filename.\n"
+"Returns 0 on match and 1 on non-match\n", prog);
+}
+
+int main(int argc, char *argv[])
+{
+    struct stat fd_statbuf, file_statbuf;
+    int ret;
+    int fd;
+
+    if (argc < 3) {
+        usage(argv[0]);
+        return 1;
+    }
+
+    fd = strtoul(argv[1], NULL, 0);
+
+    ret = fstat(fd, &fd_statbuf);
+    if (ret) {
+        return 1;
+    }
+
+    ret = stat(argv[2], &file_statbuf);
+    if (ret) {
+        return 1;
+    }
+
+    if (fd_statbuf.st_ino == file_statbuf.st_ino)
+        return 0;
+    else
+        return 1;
+}
-- 
2.24.1


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