VServer 1.9.2 (patch-2.6.8.1-vs1.9.2.diff)

[linux-2.6.git] / Documentation / binfmt_misc.txt

diff --git a/Documentation/binfmt_misc.txt b/Documentation/binfmt_misc.txt
index 3de8edb..d097f09 100644 (file)
--- a/Documentation/binfmt_misc.txt
+++ b/Documentation/binfmt_misc.txt
@@ -15,7 +15,7 @@ First you must mount binfmt_misc:
        mount binfmt_misc -t binfmt_misc /proc/sys/fs/binfmt_misc 
 
 To actually register a new binary type, you have to set up a string looking like
-:name:type:offset:magic:mask:interpreter: (where you can choose the ':' upon
+:name:type:offset:magic:mask:interpreter:flags (where you can choose the ':' upon
 your needs) and echo it to /proc/sys/fs/binfmt_misc/register.
 Here is what the fields mean:
  - 'name' is an identifier string. A new /proc file will be created with this
@@ -34,6 +34,28 @@ Here is what the fields mean:
    The mask is anded with the byte sequence of the file.
  - 'interpreter' is the program that should be invoked with the binary as first
    argument (specify the full path)
+ - 'flags' is an optional field that controls several aspects of the invocation
+   of the interpreter. It is a string of capital letters, each controls a certain
+   aspect. The following flags are supported -
+      '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. This feature should
+            be used with care - the interpreter has to be trusted not to emit
+            the contents of the non-readable binary.
+      'C' - credentials. Currently, the behavior of binfmt_misc is to calculate
+            the credentials and security token of the new process according to
+            the interpreter. When this flag is included, these attributes are
+            calculated according to the binary. It also implies the 'O' flag.
+            This feature should be used with care as the interpreter
+            will run with root permissions when a setuid binary owned by root
+            is run with binfmt_misc.
+
 
 There are some restrictions:
  - the whole register string may not exceed 255 characters
@@ -83,9 +105,9 @@ If you want to pass special arguments to your interpreter, you can
 write a wrapper script for it. See Documentation/java.txt for an
 example.
 
-Your interpreter should NOT look in the PATH for the filename; the
-kernel passes it the full filename to use.  Using the PATH can cause
-unexpected behaviour and be a security hazard.
+Your interpreter should NOT look in the PATH for the filename; the kernel
+passes it the full filename (or the file descriptor) to use.  Using $PATH can
+cause unexpected behaviour and can be a security hazard.
 
 
 There is a web page about binfmt_misc at