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Index: libexec/rtld-elf/rtld.1
===================================================================
--- libexec/rtld-elf/rtld.1
+++ libexec/rtld-elf/rtld.1
@@ -28,7 +28,7 @@
.\"
.\" $FreeBSD$
.\"
-.Dd March 16, 2017
+.Dd May 20, 2017
.Dt RTLD 1
.Os
.Sh NAME
@@ -60,10 +60,11 @@
.Pp
When resolving dependencies for the loaded objects,
.Nm
-may be allowed to translate dynamic token strings in rpath and soname
-by setting
+translates dynamic token strings in rpath and soname.
+If the
.Fl "z origin"
-option of the static linker
+option of the static linker was set when linking the binary,
+the token expansion is performed at the object load time, see
.Xr ld 1 .
The following strings are recognized now:
.Bl -tag -width ".Pa $PLATFORM"
@@ -282,6 +283,76 @@
Normally, the filtees are opened at the time of the first symbol resolution
from the filter object.
.El
+.Sh DIRECT EXECUTION MODE
+.Nm
+is typically used implicitly, loaded by the kernel as requested by the
+.Dv PT_INTERP
+program header of executed binary.
+.Fx
+also supports a direct execution mode for the dynamic linker.
+In this mode, user explicitely executes
+.Nm
+and provides the path of the program to be linked and executed, as
+an argument.
+The mode allows use of a non-standard dynamic linker for a program
+activation without changing the binary.
+Execution options may be specified.
+.Pp
+The syntax of the direct invocation is
+.Bd -ragged -offset indent
+.Pa /libexec/ld-elf.so.1
+.Op Fl f Ar fd
+.Op Fl p
+.Op Fl -
+.Pa image_path
+.Op Ar image arguments
+.Ed
+.Pp
+The options are as follows:
+.Bl -tag -width indent
+.It Fl f Ar fd
+File descriptor index
+.Ar fd
+references the binary to be activated by
+.Nm .
+It must already be opened in the process when executing
+.Nm .
+If this option is specified,
+.Ar image_path
+is only used to provide
+.Va argv[0]
+value to the program.
+.It Fl p
+If the
+.Pa image_path
+argument specifies a name which does not contain a slash
+.Dq Li /
+character,
+.Nm
+uses the search path provided by the environment variable
+.Dv PATH
+to find the binary to execute.
+.It Fl -
+Ends the
+.Nm
+options.
+The argument following
+.Fl -
+is interpreted as the path of binary to execute.
+.El
+.Pp
+To conform to user expectation to not break some naively restricted
+execution environments, in the direct execution mode
+.Nm
+emulates verification of the binary execute permission
+for current user.
+The verification only uses Unix
+.Dv DACs ,
+ignores
+.Dv ACLs
+and is racy by its nature.
+The environments which rely on such restrictions are weak
+and breakable on its own.
.Sh FILES
.Bl -tag -width ".Pa /var/run/ld-elf32.so.hints" -compact
.It Pa /var/run/ld-elf.so.hints

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