[UNIKRAFT PATCH 6/7] lib/vfscore: Expose max fds to sysconf

[Cristian Banu <cristb@xxxxxxxxx>]

Expose FDTABLE_MAX_FILES from vfscore as the return value of
sysconf(_SC_OPEN_MAX) if CONFIG_LIBVFSCORE is enabled.

This allows language runtimes to inspect the number of active
fds (e.g. for tests).

Signed-off-by: Cristian Banu <cristb@xxxxxxxxx>
---
 lib/posix-sysinfo/sysinfo.c        | 10 ++++++++++
 lib/vfscore/fd.c                   |  2 --
 lib/vfscore/include/vfscore/file.h |  3 +++
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/lib/posix-sysinfo/sysinfo.c b/lib/posix-sysinfo/sysinfo.c
index 7bcfc8b..075f320 100644
--- a/lib/posix-sysinfo/sysinfo.c
+++ b/lib/posix-sysinfo/sysinfo.c
@@ -43,6 +43,11 @@
 #include <sys/sysinfo.h>
 #include <uk/syscall.h>
 
+#if CONFIG_LIBVFSCORE
+/* For FDTABLE_MAX_FILES. */
+#include <vfscore/file.h>
+#endif
+
 static struct utsname utsname = {
        .sysname        = "Unikraft",
        .nodename       = "unikraft",
@@ -85,6 +90,11 @@ long sysconf(int name)
        if (name == _SC_PAGESIZE)
                return __PAGE_SIZE;
 
+#if CONFIG_LIBVFSCORE
+       if (name == _SC_OPEN_MAX)
+               return FDTABLE_MAX_FILES;
+#endif
+
        return 0;
 }
 
diff --git a/lib/vfscore/fd.c b/lib/vfscore/fd.c
index 684ea50..956846f 100644
--- a/lib/vfscore/fd.c
+++ b/lib/vfscore/fd.c
@@ -42,8 +42,6 @@
 #include <errno.h>
 #include <uk/ctors.h>
 
-#define FDTABLE_MAX_FILES 1024
-
 void init_stdio(void);
 
 struct fdtable {
diff --git a/lib/vfscore/include/vfscore/file.h 
b/lib/vfscore/include/vfscore/file.h
index be23974..ec45a08 100644
--- a/lib/vfscore/include/vfscore/file.h
+++ b/lib/vfscore/include/vfscore/file.h
@@ -80,6 +80,9 @@ int fdrop(struct vfscore_file* fp);
 
 #define FOF_OFFSET  0x0800    /* Use the offset in uio argument */
 
+/* Used from posix-sysinfo to determine sysconf(_SC_OPEN_MAX). */
+#define FDTABLE_MAX_FILES 1024
+
 #ifdef __cplusplus
 }
 #endif
-- 
2.26.2