[v2,03/11] linux-user: dup the execfd on start up

Commit Message

Takashi Yamamoto May 31, 2021, 5:50 a.m. UTC

So that it can be used for other purposes (e.g. syscall.c)
after the elf loader closed it.

Signed-off-by: YAMAMOTO Takashi <[e-mail]>
---
 linux-user/main.c    | 10 +++++++++-
 linux-user/qemu.h    |  2 ++
 linux-user/syscall.c |  5 ++---
 3 files changed, 13 insertions(+), 4 deletions(-)

Patch

diff --git a/linux-user/main.c b/linux-user/main.c
index 4dfc47ad3b..a9d02f9583 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -55,6 +55,7 @@ 
 #endif
 
 char *exec_path;
+int exec_fd = -1;
 
 int singlestep;
 static const char *argv0;
@@ -693,7 +694,14 @@  int main(int argc, char **argv, char **envp)
      * Manage binfmt-misc open-binary flag
      */
     execfd = qemu_getauxval(AT_EXECFD);
-    if (execfd == 0) {
+    if (execfd > 0) {
+        /*
+         * dup execfd to a global so that it can be used after loader_exec
+         * closes it.
+         */
+
+        exec_fd = dup(execfd);
+    } else {
         execfd = open(exec_path, O_RDONLY);
         if (execfd < 0) {
             printf("Error while loading %s: %s\n", exec_path, strerror(errno));
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 3b0b6b75fe..ee4e9a1779 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -160,6 +160,8 @@  typedef struct TaskState {
 } __attribute__((aligned(16))) TaskState;
 
 extern char *exec_path;
+extern int exec_fd;
+
 void init_task_state(TaskState *ts);
 void task_settid(TaskState *);
 void stop_all_tasks(void);
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 14a63518e2..2947e79dc0 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8117,12 +8117,11 @@  static int do_openat(void *cpu_env, int dirfd, const char *pathname, int flags,
     };
 
     if (is_proc_myself(pathname, "exe")) {
-        int execfd = qemu_getauxval(AT_EXECFD);
-        if (execfd) {
+        if (exec_fd != -1) {
             char filename[PATH_MAX];
             int ret;
 
-            snprintf(filename, sizeof(filename), "/proc/self/fd/%d", execfd);
+            snprintf(filename, sizeof(filename), "/proc/self/fd/%d", exec_fd);
             ret = safe_openat(dirfd, filename, flags, mode);
             if (ret != -1) {
                 return ret;