[Libunwind-devel] [PATCH] arm: ptrace: Fix order of probing unwind tables

[Vitaly_Kuzmichev]

From: Vitaly Kuzmichev <address@hidden>

Commit 92327a3 "ARM: prefer to unwind using DWARF info"
changes order of unwind info searching to prefer DWARF (.debug_frame)
section in prior to ARM specific (.ARM.exidx). This patch only affects
local process unwinding. Now the same is done for remote unwinding.

Sometimes probing .ARM.exidx first causes backtrace truncation
after __aeabi_ldiv0 (division by 0 handler that generates SIGFPE),
because it hits [cantunwind] generated by cross-gcc for __divsi3
function copied with __aeabi_ldiv0 from libgcc.a. Perhaps, lack of
debug info for __divsi3 causes [cantunwind], or there is a problem
converting DWARF to ARM unwind tables, but when unwinding using
DWARF, it hits proper entry, and backtrace is shown correctly.

Reported-by: Frederic Berat <address@hidden>
Signed-off-by: Vitaly Kuzmichev <address@hidden>
---
 src/ptrace/_UPT_find_proc_info.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/ptrace/_UPT_find_proc_info.c b/src/ptrace/_UPT_find_proc_info.c
index d2a37ea..b3209f4 100644
--- a/src/ptrace/_UPT_find_proc_info.c
+++ b/src/ptrace/_UPT_find_proc_info.c
@@ -131,15 +131,15 @@ _UPT_find_proc_info (unw_addr_space_t as, unw_word_t ip, 
unw_proc_info_t *pi,
     ret = tdep_search_unwind_table (as, ip, &ui->edi.di_cache,
                                     pi, need_unwind_info, arg);
 
+  if (ret == -UNW_ENOINFO && ui->edi.di_debug.format != -1)
+    ret = tdep_search_unwind_table (as, ip, &ui->edi.di_debug, pi,
+                                    need_unwind_info, arg);
+
 #if UNW_TARGET_ARM
   if (ret == -UNW_ENOINFO && ui->edi.di_arm.format != -1)
     ret = tdep_search_unwind_table (as, ip, &ui->edi.di_arm, pi,
                                     need_unwind_info, arg);
 #endif
 
-  if (ret == -UNW_ENOINFO && ui->edi.di_debug.format != -1)
-    ret = tdep_search_unwind_table (as, ip, &ui->edi.di_debug, pi,
-                                    need_unwind_info, arg);
-
   return ret;
 }
-- 
1.9.1