[Qemu-devel] [PATCH] Introduce --enable-binfmt-misc configure option

["Kirill A. Shutemov" <kirill@shutemov.name>]

It makes qemu compatible with binfmt_misc's flags 'P' and 'O'.

'P' - preserve-argv[0].  Legacy behavior of binfmt_misc is to overwrite the
      original argv[0] with the full path to the binary.  When this flag is
      included, binfmt_misc will add an argument to the argument vector for
      this purpose, thus preserving the original argv[0].

'O' - open-binary. Legacy behavior of binfmt_misc is to pass the full path
      of the binary to the interpreter as an argument. When this flag is
      included, binfmt_misc will open the file for reading and pass its
      descriptor as an argument, instead of the full path, thus allowing
      the interpreter to execute non-readable binaries.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
---
 configure              |   86 ++++++++++++++++++++++++++----------------------
 linux-user/linuxload.c |    7 +---
 linux-user/main.c      |   39 ++++++++++++++++++++-
 linux-user/qemu.h      |    2 +-
 4 files changed, 87 insertions(+), 47 deletions(-)

diff --git a/configure b/configure
index f14739b..0148b72 100755
--- a/configure
+++ b/configure
@@ -113,6 +113,7 @@ aio="yes"
 nptl="yes"
 mixemu="no"
 bluez="yes"
+binfmt_misc="no"
 
 # OS specific
 targetos=`uname -s`
@@ -349,6 +350,8 @@ for opt do
   ;;
   --disable-aio) aio="no"
   ;;
+  --enable-binfmt-misc) binfmt_misc="yes"
+  ;;
   *) echo "ERROR: unknown option $opt"; show_help="yes"
   ;;
   esac
@@ -453,6 +456,7 @@ echo "  --enable-uname-release=R Return R for uname -r in usermode emulation"
 echo "  --sparc_cpu=V            Build qemu for Sparc architecture v7, v8, v8plus, v8plusa, v9"
 echo "  --disable-vde            disable support for vde network"
 echo "  --disable-aio            disable AIO support"
+echo "  --enable-binfmt-misc     makes usermode compatible with binfmt_misc's flags 'P' and 'O'"
 echo ""
 echo "NOTE: The object files are built at the place where configure is launched"
 exit 1
@@ -969,55 +973,56 @@ else
   binsuffix="/bin"
 fi
 
-echo "Install prefix    $prefix"
-echo "BIOS directory    $prefix$datasuffix"
-echo "binary directory  $prefix$binsuffix"
+echo "Install prefix      $prefix"
+echo "BIOS directory      $prefix$datasuffix"
+echo "binary directory    $prefix$binsuffix"
 if test "$mingw32" = "no" ; then
-echo "Manual directory  $prefix$mansuffix"
-echo "ELF interp prefix $interp_prefix"
-fi
-echo "Source path       $source_path"
-echo "C compiler        $cc"
-echo "Host C compiler   $host_cc"
-echo "ARCH_CFLAGS       $ARCH_CFLAGS"
-echo "make              $make"
-echo "install           $install"
-echo "host CPU          $cpu"
-echo "host big endian   $bigendian"
-echo "target list       $target_list"
-echo "gprof enabled     $gprof"
-echo "sparse enabled    $sparse"
-echo "profiler          $profiler"
-echo "static build      $static"
-echo "-Werror enabled   $werror"
+echo "Manual directory    $prefix$mansuffix"
+echo "ELF interp prefix   $interp_prefix"
+fi
+echo "Source path         $source_path"
+echo "C compiler          $cc"
+echo "Host C compiler     $host_cc"
+echo "ARCH_CFLAGS         $ARCH_CFLAGS"
+echo "make                $make"
+echo "install             $install"
+echo "host CPU            $cpu"
+echo "host big endian     $bigendian"
+echo "target list         $target_list"
+echo "gprof enabled       $gprof"
+echo "sparse enabled      $sparse"
+echo "profiler            $profiler"
+echo "static build        $static"
+echo "-Werror enabled     $werror"
 if test "$darwin" = "yes" ; then
-    echo "Cocoa support     $cocoa"
+    echo "Cocoa support       $cocoa"
 fi
 echo "SDL support       $sdl"
 if test "$sdl" != "no" ; then
-    echo "SDL static link   $sdl_static"
-fi
-echo "curses support    $curses"
-echo "mingw32 support   $mingw32"
-echo "Audio drivers     $audio_drv_list"
-echo "Extra audio cards $audio_card_list"
-echo "Mixer emulation   $mixemu"
-echo "VNC TLS support   $vnc_tls"
+    echo "SDL static link     $sdl_static"
+fi
+echo "curses support      $curses"
+echo "mingw32 support     $mingw32"
+echo "Audio drivers       $audio_drv_list"
+echo "Extra audio cards   $audio_card_list"
+echo "Mixer emulation     $mixemu"
+echo "VNC TLS support     $vnc_tls"
 if test "$vnc_tls" = "yes" ; then
-    echo "    TLS CFLAGS    $vnc_tls_cflags"
-    echo "    TLS LIBS      $vnc_tls_libs"
+    echo "    TLS CFLAGS      $vnc_tls_cflags"
+    echo "    TLS LIBS        $vnc_tls_libs"
 fi
 if test -n "$sparc_cpu"; then
-    echo "Target Sparc Arch $sparc_cpu"
+    echo "Target Sparc Arch   $sparc_cpu"
 fi
-echo "kqemu support     $kqemu"
-echo "brlapi support    $brlapi"
-echo "Documentation     $build_docs"
+echo "kqemu support       $kqemu"
+echo "brlapi support      $brlapi"
+echo "Documentation       $build_docs"
 [ ! -z "$uname_release" ] && \
-echo "uname -r          $uname_release"
-echo "NPTL support      $nptl"
-echo "vde support       $vde"
-echo "AIO support       $aio"
+echo "uname -r            $uname_release"
+echo "NPTL support        $nptl"
+echo "vde support         $vde"
+echo "AIO support         $aio"
+echo "binfmt_misc support $binfmt_misc"
 
 if test $sdl_too_old = "yes"; then
 echo "-> Your SDL version is too old - please upgrade to have SDL support"
@@ -1584,6 +1589,9 @@ if test "$target_user_only" = "yes" -a "$elfload32" = "yes"; then
   echo "TARGET_HAS_ELFLOAD32=yes" >> $config_mak
   echo "#define TARGET_HAS_ELFLOAD32 1" >> $config_h
 fi
+if test "$target_user_only" = "yes" -a "$binfmt_misc" = "yes"; then
+  echo "#define BINFMT_MISC 1" >> $config_h
+fi
 
 test -f ${config_h}~ && cmp -s $config_h ${config_h}~ && mv ${config_h}~ $config_h
 
diff --git a/linux-user/linuxload.c b/linux-user/linuxload.c
index ada7c69..cbd90f7 100644
--- a/linux-user/linuxload.c
+++ b/linux-user/linuxload.c
@@ -154,7 +154,7 @@ abi_ulong loader_build_argptr(int envc, int argc, abi_ulong sp,
     return sp;
 }
 
-int loader_exec(const char * filename, char ** argv, char ** envp,
+int loader_exec(int fd, const char * filename, char ** argv, char ** envp,
              struct target_pt_regs * regs, struct image_info *infop)
 {
     struct linux_binprm bprm;
@@ -164,10 +164,7 @@ int loader_exec(const char * filename, char ** argv, char ** envp,
     bprm.p = TARGET_PAGE_SIZE*MAX_ARG_PAGES-sizeof(unsigned int);
     for (i=0 ; i<MAX_ARG_PAGES ; i++)       /* clear page-table */
             bprm.page[i] = 0;
-    retval = open(filename, O_RDONLY);
-    if (retval < 0)
-        return retval;
-    bprm.fd = retval;
+    bprm.fd = fd;
     bprm.filename = (char *)filename;
     bprm.argc = count(argv);
     bprm.argv = argv;
diff --git a/linux-user/main.c b/linux-user/main.c
index fef4bf7..25b2867 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -26,6 +26,7 @@
 
 #include "qemu.h"
 #include "qemu-common.h"
+#include "elf.h"
 /* For tb_lock */
 #include "exec-all.h"
 
@@ -2217,9 +2218,10 @@ void init_task_state(TaskState *ts)
     ts->sigqueue_table[i].next = NULL;
 }
  
-int main(int argc, char **argv)
+int main(int argc, char **argv, char **envp)
 {
     const char *filename;
+    int fd = -1;
     const char *cpu_model;
     struct target_pt_regs regs1, *regs = &regs1;
     struct image_info info1, *info = &info1;
@@ -2380,7 +2382,40 @@ int main(int argc, char **argv)
     }
     *dst = NULL; /* NULL terminate target_environ */
 
-    if (loader_exec(filename, argv+optind, target_environ, regs, info) != 0) {
+#ifdef BINFMT_MISC
+#if HOST_LONG_BITS == 32
+#define Elf_Dyn Elf32_Dyn
+#else
+#define Elf_Dyn Elf64_Dyn
+#endif
+    {
+        Elf_Dyn *auxv;
+
+        optind++; /* Handle binfmt_misc's option 'P' */
+
+        /* Handle binfmt_misc's option 'O' */
+        while(*envp++ != NULL); /* skip envp. we are on auxv now */
+        for(auxv = (Elf_Dyn *)envp; auxv->d_tag != AT_NULL; auxv++) {
+            if( auxv->d_tag == AT_EXECFD) {
+                fd = auxv->d_un.d_val;
+                break;
+            }
+        }
+
+        if (fd < 0) {
+            printf("Cannot find binary file descriptor\n");
+            _exit(1);
+        }
+    }
+#else
+    fd = open(filename, O_RDONLY);
+    if (fd < 0) {
+        printf("Cannot open file %s: %s\n", filename, strerror(errno));
+        _exit(1);
+    }
+#endif
+
+    if (loader_exec(fd, filename, argv+optind, target_environ, regs, info) != 0) {
         printf("Error loading %s\n", filename);
         _exit(1);
     }
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index a2abe51..52835ec 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -168,7 +168,7 @@ struct linux_binprm {
 void do_init_thread(struct target_pt_regs *regs, struct image_info *infop);
 abi_ulong loader_build_argptr(int envc, int argc, abi_ulong sp,
                               abi_ulong stringp, int push_ptr);
-int loader_exec(const char * filename, char ** argv, char ** envp,
+int loader_exec(int fd, const char * filename, char ** argv, char ** envp,
              struct target_pt_regs * regs, struct image_info *infop);
 
 int load_elf_binary(struct linux_binprm * bprm, struct target_pt_regs * regs,
-- 
1.5.6.5.GIT