[3/3] Use ARM-specific unwinding tables in unw_step

Message ID 1300819028-31314-4-git-send-email-ken.werner@linaro.org
State New
Headers show

Commit Message

Ken Werner March 22, 2011, 6:37 p.m.
From: Zachary T Welch <zwelch@codesourcery.com>

Uses ex_tables routines to provide a new means of unwinding the stack.
Set UNW_ARM_UNWIND_METHOD=4 to use ARM-specific unwinding tables.

Signed-off-by: Ken Werner <ken.werner@linaro.org>
---
 include/tdep-arm/libunwind_i.h |    1 +
 src/arm/Ginit_local.c          |    4 +++
 src/arm/Gstep.c                |   58 ++++++++++++++++++++++++++++++++++++++-
 3 files changed, 61 insertions(+), 2 deletions(-)

Patch

diff --git a/include/tdep-arm/libunwind_i.h b/include/tdep-arm/libunwind_i.h
index 21628cf..acaf6d7 100644
--- a/include/tdep-arm/libunwind_i.h
+++ b/include/tdep-arm/libunwind_i.h
@@ -260,6 +260,7 @@  extern int tdep_access_fpreg (struct cursor *c, unw_regnum_t reg,
 #define UNW_ARM_METHOD_ALL          0xFF
 #define UNW_ARM_METHOD_DWARF        0x01
 #define UNW_ARM_METHOD_FRAME        0x02
+#define UNW_ARM_METHOD_EXIDX        0x04
 
 #define unwi_unwind_method   UNW_OBJ(unwind_method)
 extern int unwi_unwind_method;
diff --git a/src/arm/Ginit_local.c b/src/arm/Ginit_local.c
index debf5bb..8a4ae3e 100644
--- a/src/arm/Ginit_local.c
+++ b/src/arm/Ginit_local.c
@@ -47,6 +47,10 @@  unw_init_local (unw_cursor_t *cursor, ucontext_t *uc)
 
   c->dwarf.as = unw_local_addr_space;
   c->dwarf.as_arg = uc;
+
+  if (UNW_TRY_METHOD (UNW_ARM_METHOD_EXIDX))
+    arm_exidx_init_local ();
+
   return common_init (c, 1);
 }
 
diff --git a/src/arm/Gstep.c b/src/arm/Gstep.c
index 5eac5f0..90c5f5b 100644
--- a/src/arm/Gstep.c
+++ b/src/arm/Gstep.c
@@ -1,5 +1,6 @@ 
 /* libunwind - a platform-independent unwind library
    Copyright (C) 2008 CodeSourcery
+   Copyright 2011 Linaro Limited
 
 This file is part of libunwind.
 
@@ -24,6 +25,48 @@  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 
 #include "unwind_i.h"
 #include "offsets.h"
+#include "ex_tables.h"
+
+static inline int
+arm_exidx_step (struct cursor *c)
+{
+  unw_word_t old_ip, old_cfa;
+  struct arm_exidx_table *table;
+  struct arm_exidx_entry *entry;
+  uint8_t buf[32];
+  int ret;
+
+  old_ip = c->dwarf.ip;
+  old_cfa = c->dwarf.cfa;
+
+  /* mark PC unsaved */
+  c->dwarf.loc[UNW_ARM_R15] = DWARF_NULL_LOC;
+
+  table = arm_exidx_table_find ((void *)c->dwarf.ip);
+  if (NULL == table)
+    return -UNW_ENOINFO;
+
+  entry = arm_exidx_table_lookup (table, (void *)c->dwarf.ip);
+  if (NULL == entry)
+    return -UNW_ENOINFO;
+
+  ret = arm_exidx_extract (entry, buf);
+  if (ret < 0)
+    return ret;
+
+  ret = arm_exidx_decode (buf, ret, &c->dwarf);
+  if (ret < 0)
+    return ret;
+
+  if (c->dwarf.ip == old_ip && c->dwarf.cfa == old_cfa) 
+    {
+      Dprintf ("%s: ip and cfa unchanged; stopping here (ip=0x%lx)\n",
+	       __FUNCTION__, (long) c->dwarf.ip);
+      return -UNW_EBADFRAME;
+    }
+
+  return (c->dwarf.ip == 0) ? 0 : 1;
+}
 
 PROTECTED int
 unw_step (unw_cursor_t *cursor)
@@ -33,8 +76,7 @@  unw_step (unw_cursor_t *cursor)
 
   Debug (1, "(cursor=%p)\n", c);
 
-  /* Try DWARF-based unwinding...  this is the only method likely to work for
-     ARM.  */
+  /* First, try DWARF-based unwinding. */
   if (UNW_TRY_METHOD(UNW_ARM_METHOD_DWARF))
     {
       ret = dwarf_step (&c->dwarf);
@@ -50,6 +92,18 @@  unw_step (unw_cursor_t *cursor)
       }
     }
 
+  /* Next, try extbl-based unwinding. */
+  if (UNW_TRY_METHOD (UNW_ARM_METHOD_EXIDX))
+    {
+      ret = arm_exidx_step (c);
+      if (ret >= 0)
+        return 1;
+      if (ret == -UNW_ESTOPUNWIND)
+	return 0;
+    }
+
+  /* Fall back on APCS frame parsing.
+     Note: This won't work in case the ARM EABI is used. */
   if (unlikely (ret < 0))
     {
       if (UNW_TRY_METHOD(UNW_ARM_METHOD_FRAME))