Allow older GDB to build against newer glibc

Also, fix the subdir used when only gdbserver is built (without native
GDB).

Signed-off-by: Alexey Neyman <stilor@att.net>

config/debug/gdb.in

@@ -33,7 +33,10 @@ config GDB_DEP_CXX11
     select GDB_REQUIRE_older_than_8_0
 
 config GDB_HAS_IPA_LIB
-    bool
+    def_bool y
     depends on GDB_7_2_or_later
-    default y
 
+# Does GDB need ps_get_thread_area with const qualifier?
+config GDB_CONST_GET_THREAD_AREA
+    bool
+    default y if GDB_older_than_7_12

packages/gdb/7.11.1/0005-include-gregset.h.patch

@@ -0,0 +1,73 @@
+commit 31925464a80970e37c06192a0c49f8948a2f5da0
+Author: Matthew Wahab <matthew.wahab@arm.com>
+Date:   Mon Aug 15 13:09:04 2016 +0100
+
+    [GDB] Fix builds broken by proc-service changes.
+    
+    GLIBC BZ#20311 introduced a change to install proc_service.h so that gdb
+    didn't have to use the version it embeds in gdb_proc_service.h. The
+    embedded version is guarded by HAVE_PROC_SERVICE_H and
+    gdb_proc_service.h has a number other of includes and definitions, all
+    of which are uncondional except for an include for gregset.h. This is
+    only included if HAVE_PROC_SERIVCE_H is not defined.
+    
+    This causes a build failure when cross compiling gdb with the latest
+    glibc because type definitions in gregset are used independently of
+    HAVE_PROC_SERIVCE_H. In particular, they are used in gdb_proc_service.h
+    when PRFPREGSET_T_BROKEN is set.
+    
+    The error messages on the failure are
+    ----
+    binutils-gdb/gdb/gdb_proc_service.h:173:9: error: ‘gdb_fpregset_t’ does
+    not name a type; did you mean ‘elf_fpregset_t’?
+     typedef gdb_fpregset_t gdb_prfpregset_t;
+             ^~~~~~~~~~~~~~
+             elf_fpregset_t
+    
+    binutils-gdb/gdb/gdb_proc_service.h:173:9: error: ‘gdb_fpregset_t’ does
+    not name a type; did you mean ‘elf_fpregset_t’?
+     typedef gdb_fpregset_t gdb_prfpregset_t;
+             ^~~~~~~~~~~~~~
+             elf_fpregset_t
+    
+    binutils-gdb/gdb/proc-service.c:218:15: error: ‘gdb_prfpregset_t’ does
+    not name a type; did you mean ‘gdb_fpregset_t’?
+             const gdb_prfpregset_t *fpregset)
+                   ^~~~~~~~~~~~~~~~
+                   gdb_fpregset_t
+    ----
+    
+    This patch moves the include for gregset.h to before the code guarded by
+    HAVE_PROC_SERIVCE_H, so that it is always included. This is enough to
+    fix the build.
+    
+    2016-08-15  Matthew Wahab  <matthew.wahab@arm.com>
+    
+            PR gdb/20457
+            * gdb_proc_service.h: Add an include of gregset.h
+            [!HAVE_PROC_SERVICE_H]: Remove the include of gregset.h.
+
+---
+ gdb/gdb_proc_service.h |    4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+--- a/gdb/gdb_proc_service.h
++++ b/gdb/gdb_proc_service.h
+@@ -21,6 +21,8 @@
+ 
+ #include <sys/types.h>
+ 
++#include "gregset.h"
++
+ #ifdef HAVE_PROC_SERVICE_H
+ 
+ /* glibc's proc_service.h doesn't wrap itself with extern "C".  Need
+@@ -60,8 +62,6 @@
+ #include <sys/procfs.h>
+ #endif
+ 
+-#include "gregset.h"
+-
+ EXTERN_C_PUSH
+ 
+ /* Functions in this interface return one of these status codes.  */

scripts/build/debug/300-gdb.sh

@@ -122,7 +122,7 @@ do_debug_gdb_build()
                 gdbserver_extra_config+=("--disable-inprocess-agent")
             fi
             if [ "${CT_GDB_NATIVE}" != "y" ]; then
-                subdir=gdbserver/
+                subdir=gdb/gdbserver/
             fi
         fi
 
@@ -175,6 +175,22 @@ do_gdb_backend()
         esac
     done
 
+    # Starting with glibc 2.25, it now provides a <proc_service.h> header. The
+    # problem is that GDB releases prior to 7.12 used to implement one of the
+    # interfaces, ps_get_thread_are with a const qualifier on one of the arguments.
+    # Therefore, such older versions cannot be compiled against a newer glibc.
+    # If we detect such a combination, mitigate by creating a local proc_service.h
+    # with a prototype adjusted for GDB requirements.
+    if [ -r "${CT_HEADERS_DIR}/proc_service.h" -a "${CT_GDB_CONST_GET_THREAD_AREA}" = "y" ]; then
+        CT_DoLog DEBUG "Fixing up the prototype in <proc_service.h>"
+        CT_DoExecLog ALL mkdir -p gdb/gdbserver
+        CT_DoExecLog ALL cp "${CT_HEADERS_DIR}/proc_service.h" gdb/proc_service.h
+        CT_DoExecLog ALL sed -i \
+            "s/\(ps_get_thread_area *(\).*\(struct ps_prochandle\)/\1const \2/" \
+            gdb/proc_service.h
+        CT_DoExecLog ALL cp gdb/proc_service.h gdb/gdbserver/proc_service.h
+    fi
+
     if [ "${CT_GDB_HAS_PKGVERSION_BUGURL}" = "y" ]; then
         [ -n "${CT_PKGVERSION}" ] && extra_config+=("--with-pkgversion=${CT_PKGVERSION}")
         [ -n "${CT_TOOLCHAIN_BUGURL}" ] && extra_config+=("--with-bugurl=${CT_TOOLCHAIN_BUGURL}")