bsd-user: Implement get_filename_from_fd.

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Karim Taha <kariem.taha2.7@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Warner Losh <imp@bsdimp.com>
Message-Id: <20230925182425.3163-20-kariem.taha2.7@gmail.com>

bsd-user/freebsd/meson.build

@@ -1,5 +1,6 @@
 bsd_user_ss.add(files(
   'os-stat.c',
+  'os-proc.c',
   'os-sys.c',
   'os-syscall.c',
 ))

bsd-user/freebsd/os-proc.c

@@ -0,0 +1,82 @@
+/*
+ *  FreeBSD process related emulation code
+ *
+ *  Copyright (c) 2013-15 Stacey D. Son
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+#include "qemu/osdep.h"
+
+#include <sys/param.h>
+#include <sys/queue.h>
+#include <sys/sysctl.h>
+struct kinfo_proc;
+#include <libprocstat.h>
+
+#include "qemu.h"
+
+/*
+ * Get the filename for the given file descriptor.
+ * Note that this may return NULL (fail) if no longer cached in the kernel.
+ */
+char *
+get_filename_from_fd(pid_t pid, int fd, char *filename, size_t len);
+char *
+get_filename_from_fd(pid_t pid, int fd, char *filename, size_t len)
+{
+    char *ret = NULL;
+    unsigned int cnt;
+    struct procstat *procstat = NULL;
+    struct kinfo_proc *kp = NULL;
+    struct filestat_list *head = NULL;
+    struct filestat *fst;
+
+    procstat = procstat_open_sysctl();
+    if (procstat == NULL) {
+        goto out;
+    }
+
+    kp = procstat_getprocs(procstat, KERN_PROC_PID, pid, &cnt);
+    if (kp == NULL) {
+        goto out;
+    }
+
+    head = procstat_getfiles(procstat, kp, 0);
+    if (head == NULL) {
+        goto out;
+    }
+
+    STAILQ_FOREACH(fst, head, next) {
+        if (fd == fst->fs_fd) {
+            if (fst->fs_path != NULL) {
+                (void)strlcpy(filename, fst->fs_path, len);
+                ret = filename;
+            }
+            break;
+        }
+    }
+
+out:
+    if (head != NULL) {
+        procstat_freefiles(procstat, head);
+    }
+    if (kp != NULL) {
+        procstat_freeprocs(procstat, kp);
+    }
+    if (procstat != NULL) {
+        procstat_close(procstat);
+    }
+    return ret;
+}
+