[PATCH 2/2] backends: Add arm frame_nregs and set_initial_registers_tid.

[Mark Wielaard <mjw at redhat dot com>]

This allows CFI unwinding for ARM. It relies on having .debug_frame around
which is always the case in our testsuite. All backtrace tests PASS.

For non-debug unwinding ARM uses EXIDX tables, not .eh_frames, which
would have to be translated to CFI to do unwinding without .debug_frame
available.

Signed-off-by: Mark Wielaard <mjw@redhat.com>
---
 backends/ChangeLog                     |  7 ++++
 backends/Makefile.am                   |  2 +-
 backends/arm_init.c                    |  6 +++-
 backends/{arm_init.c => arm_initreg.c} | 58 ++++++++++++++--------------------
 4 files changed, 37 insertions(+), 36 deletions(-)
 copy backends/{arm_init.c => arm_initreg.c} (51%)

diff --git a/backends/ChangeLog b/backends/ChangeLog
index c8e2b30..212b9f6 100644
--- a/backends/ChangeLog
+++ b/backends/ChangeLog
@@ -1,3 +1,10 @@
+2014-01-26  Mark Wielaard  <mjw@redhat.com>
+
+	* Makefile.am (arm_SRCS): Add arm_initreg.c.
+	* arm_init.c (arm_init): Define frame_nregs and hook
+	set_initial_registers_tid.
+	* arm_initreg.c: New file.
+
 2014-01-25  Mark Wielaard  <mjw@redhat.com>
 
 	* arm_cfi.c (arm_abi_cfi): Restore SP (r13) from CFA.
diff --git a/backends/Makefile.am b/backends/Makefile.am
index 90e93a8..4129eee 100644
--- a/backends/Makefile.am
+++ b/backends/Makefile.am
@@ -78,7 +78,7 @@ libebl_alpha_pic_a_SOURCES = $(alpha_SRCS)
 am_libebl_alpha_pic_a_OBJECTS = $(alpha_SRCS:.c=.os)
 
 arm_SRCS = arm_init.c arm_symbol.c arm_regs.c arm_corenote.c \
-	   arm_auxv.c arm_attrs.c arm_retval.c arm_cfi.c
+	   arm_auxv.c arm_attrs.c arm_retval.c arm_cfi.c arm_initreg.c
 libebl_arm_pic_a_SOURCES = $(arm_SRCS)
 am_libebl_arm_pic_a_OBJECTS = $(arm_SRCS:.c=.os)
 
diff --git a/backends/arm_init.c b/backends/arm_init.c
index cf661ce..14b2635 100644
--- a/backends/arm_init.c
+++ b/backends/arm_init.c
@@ -1,5 +1,5 @@
 /* Initialization of Arm specific backend library.
-   Copyright (C) 2002, 2005, 2009, 2013 Red Hat, Inc.
+   Copyright (C) 2002, 2005, 2009, 2013, 2014 Red Hat, Inc.
    This file is part of elfutils.
    Written by Ulrich Drepper <drepper@redhat.com>, 2002.
 
@@ -64,5 +64,9 @@ arm_init (elf, machine, eh, ehlen)
   HOOK (eh, return_value_location);
   HOOK (eh, abi_cfi);
 
+  /* We only unwind the core integer registers.  */
+  eh->frame_nregs = 16;
+  HOOK (eh, set_initial_registers_tid);
+
   return MODVERSION;
 }
diff --git a/backends/arm_init.c b/backends/arm_initreg.c
similarity index 51%
copy from backends/arm_init.c
copy to backends/arm_initreg.c
index cf661ce..c03146e 100644
--- a/backends/arm_init.c
+++ b/backends/arm_initreg.c
@@ -1,7 +1,6 @@
-/* Initialization of Arm specific backend library.
-   Copyright (C) 2002, 2005, 2009, 2013 Red Hat, Inc.
+/* Fetch live process registers from TID.
+   Copyright (C) 2014 Red Hat, Inc.
    This file is part of elfutils.
-   Written by Ulrich Drepper <drepper@redhat.com>, 2002.
 
    This file is free software; you can redistribute it and/or modify
    it under the terms of either
@@ -31,38 +30,29 @@
 # include <config.h>
 #endif
 
-#define BACKEND		arm_
-#define RELOC_PREFIX	R_ARM_
-#include "libebl_CPU.h"
-
-/* This defines the common reloc hooks based on arm_reloc.def.  */
-#include "common-reloc.c"
+#if defined __arm__
+# include <sys/types.h>
+# include <sys/user.h>
+# include <sys/ptrace.h>
+#endif
 
+#define BACKEND arm_
+#include "libebl_CPU.h"
 
-const char *
-arm_init (elf, machine, eh, ehlen)
-     Elf *elf __attribute__ ((unused));
-     GElf_Half machine __attribute__ ((unused));
-     Ebl *eh;
-     size_t ehlen;
+bool
+arm_set_initial_registers_tid (pid_t tid __attribute__ ((unused)),
+			  ebl_tid_registers_t *setfunc __attribute__ ((unused)),
+			       void *arg __attribute__ ((unused)))
 {
-  /* Check whether the Elf_BH object has a sufficent size.  */
-  if (ehlen < sizeof (Ebl))
-    return NULL;
-
-  /* We handle it.  */
-  eh->name = "ARM";
-  arm_init_reloc (eh);
-  HOOK (eh, segment_type_name);
-  HOOK (eh, section_type_name);
-  HOOK (eh, machine_flag_check);
-  HOOK (eh, reloc_simple_type);
-  HOOK (eh, register_info);
-  HOOK (eh, core_note);
-  HOOK (eh, auxv_info);
-  HOOK (eh, check_object_attribute);
-  HOOK (eh, return_value_location);
-  HOOK (eh, abi_cfi);
-
-  return MODVERSION;
+#if ! defined __arm__
+  return false;
+#else
+  struct user_regs user_regs;
+  if (ptrace (PTRACE_GETREGS, tid, NULL, &user_regs) != 0)
+    return false;
+  Dwarf_Word dwarf_regs[16];
+  for (int i = 0; i < 16; i++)
+    dwarf_regs[i] = user_regs.uregs[i];
+  return setfunc (0, 16, dwarf_regs, arg);
+#endif
 }
-- 
1.8.4.2