[ppc64le] Use skip_entrypoint for skip_trampoline_code

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

ppc64le loses control when stepping between two PLT-called functions inside
a shared library:

29        shlib_second (); /* first-hit */^M
(gdb) PASS: gdb.base/solib-intra-step.exp: first-hit
step^M
^M
Program received signal SIGABRT, Aborted.^M
0x00003fffb7cbe578 in __GI_raise (sig=<optimized out>) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56^M
56        return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig);^M
(gdb) FAIL: gdb.base/solib-intra-step.exp: second-hit
->
29        shlib_second (); /* first-hit */^M
(gdb) PASS: gdb.base/solib-intra-step.exp: first-hit
step^M
shlib_second () at ./gdb.base/solib-intra-step-lib.c:23^M
23        abort (); /* second-hit */^M
(gdb) PASS: gdb.base/solib-intra-step.exp: second-hit

This is because gdbarch_skip_trampoline_code() will resolve the final function
as shlib_second+0 and place there the breakpoint, but ld.so will jump after
the breakpoint - at shlib_second+8 - as it is ELFv2 local symbol optimization:

Dump of assembler code for function shlib_second:
   0x0000000000000804 <+0>:	addis   r2,r12,2
   0x0000000000000808 <+4>:	addi    r2,r2,30668
   0x000000000000080c <+8>:	mflr    r0

Currently gdbarch_skip_entrypoint() has been called in skip_prologue_sal() and
fill_in_stop_func() but that is not enough.  I believe
gdbarch_skip_entrypoint() should be called after every
gdbarch_skip_trampoline_code(), shouldn't it?

The attached patch is a bit hack but I am not sure what is a clean solution.
Maybe create a gdbarch_skip_trampoline_code() wrapper function calling also
gdbarch_skip_entrypoint() and forbid calling gdbarch_skip_trampoline_code()
directly?

No regressions on ppc64le-rhel7-linux-gnu.


Jan

gdb/ChangeLog
2015-09-07  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* ppc64-tdep.c (ppc64_skip_trampoline_code): Rename to ...
	(ppc64_skip_trampoline_code_1): ... here.
	(ppc64_skip_trampoline_code): New wrapper function.

gdb/testsuite/ChangeLog
2015-09-07  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.base/solib-intra-step-lib.c: New file.
	* gdb.base/solib-intra-step-main.c: New file.
	* gdb.base/solib-intra-step.exp: New file.

diff --git a/gdb/ppc64-tdep.c b/gdb/ppc64-tdep.c
index bb23b6a..d3c0ece 100644
--- a/gdb/ppc64-tdep.c
+++ b/gdb/ppc64-tdep.c
@@ -454,8 +454,8 @@ ppc64_standard_linkage4_target (struct frame_info *frame,
    When the execution direction is EXEC_REVERSE, scan backward to
    check whether we are in the middle of a PLT stub.  */
 
-CORE_ADDR
-ppc64_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc)
+static CORE_ADDR
+ppc64_skip_trampoline_code_1 (struct frame_info *frame, CORE_ADDR pc)
 {
 #define MAX(a,b) ((a) > (b) ? (a) : (b))
   unsigned int insns[MAX (MAX (MAX (ARRAY_SIZE (ppc64_standard_linkage1),
@@ -530,6 +530,18 @@ ppc64_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc)
   return 0;
 }
 
+/* Wrapper of ppc64_skip_trampoline_code_1 checking also
+   ppc_elfv2_skip_entrypoint.  */
+
+CORE_ADDR
+ppc64_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc)
+{
+  pc = ppc64_skip_trampoline_code_1 (frame, pc);
+  if (pc != 0)
+    pc = gdbarch_skip_entrypoint (get_frame_arch (frame), pc);
+  return pc;
+}
+
 /* Support for convert_from_func_ptr_addr (ARCH, ADDR, TARG) on PPC64
    GNU/Linux.
 
diff --git a/gdb/testsuite/gdb.base/solib-intra-step-lib.c b/gdb/testsuite/gdb.base/solib-intra-step-lib.c
new file mode 100644
index 0000000..07b72cf
--- /dev/null
+++ b/gdb/testsuite/gdb.base/solib-intra-step-lib.c
@@ -0,0 +1,30 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <stdlib.h>
+
+void
+shlib_second (void)
+{
+  abort (); /* second-hit */
+}
+
+void
+shlib_first (void)
+{
+  shlib_second (); /* first-hit */
+}
diff --git a/gdb/testsuite/gdb.base/solib-intra-step-main.c b/gdb/testsuite/gdb.base/solib-intra-step-main.c
new file mode 100644
index 0000000..186bd5f
--- /dev/null
+++ b/gdb/testsuite/gdb.base/solib-intra-step-main.c
@@ -0,0 +1,25 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+extern void shlib_first (void);
+
+int
+main (void)
+{
+  shlib_first ();
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/solib-intra-step.exp b/gdb/testsuite/gdb.base/solib-intra-step.exp
new file mode 100644
index 0000000..5666ede
--- /dev/null
+++ b/gdb/testsuite/gdb.base/solib-intra-step.exp
@@ -0,0 +1,52 @@
+# Copyright 2015 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+standard_testfile
+
+if {[skip_shlib_tests]} {
+    return 0
+}
+
+# Library file.
+set libname "${testfile}-lib"
+set srcfile_lib ${srcdir}/${subdir}/${libname}.c
+set binfile_lib [standard_output_file ${libname}.so]
+set lib_flags [list debug]
+# Binary file.
+set testfile "${testfile}-main"
+set srcfile ${srcdir}/${subdir}/${testfile}.c
+set binfile [standard_output_file ${testfile}]
+set bin_flags [list debug shlib=${binfile_lib}]
+
+if [get_compiler_info] {
+    return -1
+}
+
+if { [gdb_compile_shlib ${srcfile_lib} ${binfile_lib} $lib_flags] != ""
+     || [gdb_compile ${srcfile} ${binfile} executable $bin_flags] != "" } {
+  untested "Could not compile $binfile_lib or $binfile."
+  return -1
+}
+
+clean_restart ${binfile}
+gdb_load_shlibs $binfile_lib
+
+if ![runto_main] then {
+  return 0
+}
+
+gdb_test "step" " first-hit .*" "first-hit"
+
+gdb_test "step" " second-hit .*" "second-hit"