[PATCH 1/3] linux user: make execfd global (like exec path) and keep it open

* [PATCH 1/3] linux user: make execfd global (like exec path) and keep it open
@ 2020-08-17 23:57 Andrew Aladjev
  2020-08-17 23:57 ` [PATCH 2/3] linux user: moving is proc functions to separate file Andrew Aladjev
                   ` (2 more replies)
  0 siblings, 3 replies; 7+ messages in thread
From: Andrew Aladjev @ 2020-08-17 23:57 UTC (permalink / raw)
  To: qemu-devel; +Cc: Andrew Aladjev

User opens /proc/self/exe symlink, than kernel should create /proc/self/fd/<execfd> symlink. We should be able to detect both exe and fd/<execfd> symlinks to provide common behaviour. The easiest solution is to make execfd global and keep it open. This solution looks acceptable because exec_path is already global.

Signed-off-by: Andrew Aladjev <aladjev.andrew@gmail.com>
---
 linux-user/elfload.c |  3 ++-
 linux-user/exit.c    |  7 +++++--
 linux-user/main.c    |  2 +-
 linux-user/qemu.h    |  1 +
 linux-user/syscall.c | 18 ++++++++++++++----
 5 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index fe9dfe795d..dfaf937ab9 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2363,6 +2363,7 @@ void probe_guest_base(const char *image_name, abi_ulong guest_loaddr,
 
    IMAGE_NAME is the filename of the image, to use in error messages.
    IMAGE_FD is the open file descriptor for the image.
+   WARNING: IMAGE_FD won't be closed.
 
    BPRM_BUF is a copy of the beginning of the file; this of course
    contains the elf file header at offset 0.  It is assumed that this
@@ -2632,7 +2633,6 @@ static void load_elf_image(const char *image_name, int image_fd,
 
     mmap_unlock();
 
-    close(image_fd);
     return;
 
  exit_read:
@@ -2666,6 +2666,7 @@ static void load_elf_interp(const char *filename, struct image_info *info,
     }
 
     load_elf_image(filename, fd, info, NULL, bprm_buf);
+    close(fd);
     return;
 
  exit_perror:
diff --git a/linux-user/exit.c b/linux-user/exit.c
index 1594015444..f0626fc432 100644
--- a/linux-user/exit.c
+++ b/linux-user/exit.c
@@ -28,12 +28,15 @@ extern void __gcov_dump(void);
 
 void preexit_cleanup(CPUArchState *env, int code)
 {
+    close(execfd);
+
 #ifdef CONFIG_GPROF
         _mcleanup();
 #endif
 #ifdef CONFIG_GCOV
         __gcov_dump();
 #endif
-        gdb_exit(env, code);
-        qemu_plugin_atexit_cb();
+
+    gdb_exit(env, code);
+    qemu_plugin_atexit_cb();
 }
diff --git a/linux-user/main.c b/linux-user/main.c
index 75c9785157..27644a831a 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -49,6 +49,7 @@
 #include "crypto/init.h"
 
 char *exec_path;
+int execfd;
 
 int singlestep;
 static const char *argv0;
@@ -629,7 +630,6 @@ int main(int argc, char **argv, char **envp)
     int target_argc;
     int i;
     int ret;
-    int execfd;
     int log_mask;
     unsigned long max_reserved_va;
 
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 5c964389c1..f99be78d42 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -156,6 +156,7 @@ typedef struct TaskState {
 } __attribute__((aligned(16))) TaskState;
 
 extern char *exec_path;
+extern int execfd;
 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 945fc25279..5741c72733 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7613,8 +7613,7 @@ 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);
-        return execfd ? execfd : safe_openat(dirfd, exec_path, flags, mode);
+        return execfd;
     }
 
     for (fake_open = fakes; fake_open->filename; fake_open++) {
@@ -7872,8 +7871,19 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
         return ret;
 #endif
     case TARGET_NR_close:
-        fd_trans_unregister(arg1);
-        return get_errno(close(arg1));
+        {
+            int fd = arg1;
+            if (fd == execfd) {
+                /*
+                 * We don't need to close execfd.
+                 * It will be closed on QEMU exit.
+                 */
+                return 0;
+            }
+
+            fd_trans_unregister(fd);
+            return get_errno(close(fd));
+        }
 
     case TARGET_NR_brk:
         return do_brk(arg1);
-- 
2.26.2



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