Merge tag 'pull-misc-20240805' of https://gitlab.com/rth7680/qemu into staging

linux-user/elfload: Fix pr_pid values in core files
util: Add qemu_close_all_open_fd
net/tap: Use qemu_close_all_open_fd

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* tag 'pull-misc-20240805' of https://gitlab.com/rth7680/qemu:
  net/tap: Use qemu_close_all_open_fd()
  qemu/osdep: Add excluded fd parameter to qemu_close_all_open_fd()
  net/tap: Factorize fd closing after forking
  qemu/osdep: Split qemu_close_all_open_fd() and add fallback
  qemu/osdep: Move close_all_open_fds() to oslib-posix
  linux-user/elfload: Fix pr_pid values in core files

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 124 insertions, 0 deletions

diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index b090fe0eed..11b35e48fb 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -807,3 +807,127 @@ int qemu_msync(void *addr, size_t length, int fd)
 
     return msync(addr, length, MS_SYNC);
 }
+
+static bool qemu_close_all_open_fd_proc(const int *skip, unsigned int nskip)
+{
+    struct dirent *de;
+    int fd, dfd;
+    DIR *dir;
+    unsigned int skip_start = 0, skip_end = nskip;
+
+    dir = opendir("/proc/self/fd");
+    if (!dir) {
+        /* If /proc is not mounted, there is nothing that can be done. */
+        return false;
+    }
+    /* Avoid closing the directory. */
+    dfd = dirfd(dir);
+
+    for (de = readdir(dir); de; de = readdir(dir)) {
+        bool close_fd = true;
+
+        if (de->d_name[0] == '.') {
+            continue;
+        }
+        fd = atoi(de->d_name);
+        if (fd == dfd) {
+            continue;
+        }
+
+        for (unsigned int i = skip_start; i < skip_end; i++) {
+            if (fd < skip[i]) {
+                /* We are below the next skipped fd, break */
+                break;
+            } else if (fd == skip[i]) {
+                close_fd = false;
+                /* Restrict the range as we found fds matching start/end */
+                if (i == skip_start) {
+                    skip_start++;
+                } else if (i == skip_end) {
+                    skip_end--;
+                }
+                break;
+            }
+        }
+
+        if (close_fd) {
+            close(fd);
+        }
+    }
+    closedir(dir);
+
+    return true;
+}
+
+static bool qemu_close_all_open_fd_close_range(const int *skip,
+                                               unsigned int nskip,
+                                               int open_max)
+{
+#ifdef CONFIG_CLOSE_RANGE
+    int max_fd = open_max - 1;
+    int first = 0, last;
+    unsigned int cur_skip = 0;
+    int ret;
+
+    do {
+        /* Find the start boundary of the range to close */
+        while (cur_skip < nskip && first == skip[cur_skip]) {
+            cur_skip++;
+            first++;
+        }
+
+        /* Find the upper boundary of the range to close */
+        last = max_fd;
+        if (cur_skip < nskip) {
+            last = skip[cur_skip] - 1;
+            last = MIN(last, max_fd);
+        }
+
+        /* With the adjustments to the range, we might be done. */
+        if (first > last) {
+            break;
+        }
+
+        ret = close_range(first, last, 0);
+        if (ret < 0) {
+            return false;
+        }
+
+        first = last + 1;
+    } while (last < max_fd);
+
+    return true;
+#else
+    return false;
+#endif
+}
+
+static void qemu_close_all_open_fd_fallback(const int *skip, unsigned int nskip,
+                                            int open_max)
+{
+    unsigned int cur_skip = 0;
+
+    /* Fallback */
+    for (int i = 0; i < open_max; i++) {
+        if (cur_skip < nskip && i == skip[cur_skip]) {
+            cur_skip++;
+            continue;
+        }
+        close(i);
+    }
+}
+
+/*
+ * Close all open file descriptors.
+ */
+void qemu_close_all_open_fd(const int *skip, unsigned int nskip)
+{
+    int open_max = sysconf(_SC_OPEN_MAX);
+
+    assert(skip != NULL || nskip == 0);
+
+    if (!qemu_close_all_open_fd_close_range(skip, nskip, open_max) &&
+        !qemu_close_all_open_fd_proc(skip, nskip)) {
+        qemu_close_all_open_fd_fallback(skip, nskip, open_max);
+    }
+}