Use auxiliary vector to obtain the executable path name (#24696)

This vector is populated by the kernel while loading an ELF, and is
available to user land without requiring any system calls.  This is
specially interesting if programs are executed under a chroot where
/proc isn't available (and thus realpath("/proc/self/exe"), the current
method of obtaining the full path name for the executable).

6 files changed, 37 insertions, 2 deletions

diff --git a/src/ToolBox/SOS/Strike/CMakeLists.txt b/src/ToolBox/SOS/Strike/CMakeLists.txt
index a4fe91cba3..8e0218a341 100644
--- a/src/ToolBox/SOS/Strike/CMakeLists.txt
+++ b/src/ToolBox/SOS/Strike/CMakeLists.txt
@@ -132,7 +132,6 @@ else(WIN32)
     strike.cpp
     sos.cpp
     util.cpp
-    ../../../coreclr/hosts/unixcoreruncommon/coreruncommon.cpp
   )
 
   set(SOS_LIBRARY
@@ -142,6 +141,7 @@ else(WIN32)
     # share the PAL in the dac module
     mscordaccore
     palrt
+    unixcoreruncommon
   )
 
   set(DEF_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/sos_unixexports.src)
diff --git a/src/coreclr/hosts/osxbundlerun/CMakeLists.txt b/src/coreclr/hosts/osxbundlerun/CMakeLists.txt
index 49e2248ee7..8af173f970 100644
--- a/src/coreclr/hosts/osxbundlerun/CMakeLists.txt
+++ b/src/coreclr/hosts/osxbundlerun/CMakeLists.txt
@@ -5,7 +5,6 @@ include_directories(../unixcoreruncommon)
 add_compile_options(-fPIE)
 
 set(CORERUN_SOURCES 
-    ../unixcoreruncommon/coreruncommon.cpp
     osxbundlerun.cpp 
 )
 
@@ -15,6 +14,7 @@ _add_executable(osxbundlerun
 
 target_link_libraries(osxbundlerun 
     dl
+    unixcoreruncommon
 )
 
 add_dependencies(osxbundlerun
diff --git a/src/coreclr/hosts/unixcoreruncommon/CMakeLists.txt b/src/coreclr/hosts/unixcoreruncommon/CMakeLists.txt
index a17e0a0fd6..93a5bbf9ff 100644
--- a/src/coreclr/hosts/unixcoreruncommon/CMakeLists.txt
+++ b/src/coreclr/hosts/unixcoreruncommon/CMakeLists.txt
@@ -2,6 +2,10 @@ project(unixcoreruncommon)
 
 add_compile_options(-fPIC)
 
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+
+include(configure.cmake)
+
 _add_library(unixcoreruncommon
     STATIC
     coreruncommon.cpp
diff --git a/src/coreclr/hosts/unixcoreruncommon/config.h.in b/src/coreclr/hosts/unixcoreruncommon/config.h.in
new file mode 100644
index 0000000000..0e457b411c
--- /dev/null
+++ b/src/coreclr/hosts/unixcoreruncommon/config.h.in
@@ -0,0 +1,10 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#ifndef __CONFIG_H__
+#define __CONFIG_H__
+
+#cmakedefine01 HAVE_GETAUXVAL
+
+#endif // __CONFIG_H__
diff --git a/src/coreclr/hosts/unixcoreruncommon/configure.cmake b/src/coreclr/hosts/unixcoreruncommon/configure.cmake
new file mode 100644
index 0000000000..ea90cc8a35
--- /dev/null
+++ b/src/coreclr/hosts/unixcoreruncommon/configure.cmake
@@ -0,0 +1,5 @@
+check_symbol_exists(getauxval sys/auxv.h HAVE_GETAUXVAL)
+
+configure_file(
+	${CMAKE_CURRENT_SOURCE_DIR}/config.h.in
+	${CMAKE_CURRENT_BINARY_DIR}/config.h)
diff --git a/src/coreclr/hosts/unixcoreruncommon/coreruncommon.cpp b/src/coreclr/hosts/unixcoreruncommon/coreruncommon.cpp
index fb155f69bb..0dacddbef0 100644
--- a/src/coreclr/hosts/unixcoreruncommon/coreruncommon.cpp
+++ b/src/coreclr/hosts/unixcoreruncommon/coreruncommon.cpp
@@ -6,6 +6,8 @@
 // Code that is used by both the Unix corerun and coreconsole.
 //
 
+#include "config.h"
+
 #include <cstdlib>
 #include <cstring>
 #include <assert.h>
@@ -20,6 +22,9 @@
 #include <sys/types.h>
 #include <sys/param.h>
 #endif
+#if HAVE_GETAUXVAL
+#include <sys/auxv.h>
+#endif
 #if defined(HAVE_SYS_SYSCTL_H) || defined(__FreeBSD__)
 #include <sys/sysctl.h>
 #endif
@@ -105,6 +110,17 @@ bool GetEntrypointExecutableAbsolutePath(std::string& entrypointExecutable)
         result = false;
     }
 #else
+
+#if HAVE_GETAUXVAL && defined(AT_EXECFN)
+    const char *execfn = (const char *)getauxval(AT_EXECFN);
+
+    if (execfn)
+    {
+        entrypointExecutable.assign(execfn);
+        result = true;
+    }
+    else
+#endif
     // On other OSs, return the symlink that will be resolved by GetAbsolutePath
     // to fetch the entrypoint EXE absolute path, inclusive of filename.
     result = GetAbsolutePath(symlinkEntrypointExecutable, entrypointExecutable);