[Libunwind-devel] [PATCH] dwarf: Fix incorrect application of restore_state

[Dave Watson]

Repro for a multilib binary on host x86_64:

CFLAGS="-m32" LDFLAGS="-m32" ./configure --enable-debug -- 
host=i686-pc-linux-gnu --target=i686-pc-linux-gnu --libdur=/usr/lib32 
--prefix=/usr --disable-documentation

make check

Gtest-init function fails trying to step through libc_start_main.  The CFA 
function is:

DW_CFA_def_cfa_offset: 112
DW_CFA_advance_loc: 5 to ...643
DW_CFA_restore state

Where the return address is 643.

Generally, it appears we apply all ip <= end_ip, which is incorrect in some 
circumstances.

libgcc only applies ip < end_ip + is_signal_frame, but that seems to break 
async signal handling
tests in libunwind for unknown reasons.

This is somewhat simlar to the fix in e9e8ed73e for GNU_args_size,
where the same ip check was added.
---
 src/dwarf/Gparser.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/dwarf/Gparser.c b/src/dwarf/Gparser.c
index e8eaeac8..9d405e76 100644
--- a/src/dwarf/Gparser.c
+++ b/src/dwarf/Gparser.c
@@ -289,8 +289,10 @@ run_cfi_program (struct dwarf_cursor *c, 
dwarf_state_record_t *sr,
               ret = -UNW_EINVAL;
               break;
             }
-          memcpy (&sr->rs_current, &(*rs_stack)->state, sizeof 
(sr->rs_current));
-         pop_rstate_stack(rs_stack);
+          if (*ip < end_ip) {
+            memcpy (&sr->rs_current, &(*rs_stack)->state, sizeof 
(sr->rs_current));
+            pop_rstate_stack(rs_stack);
+          }
           Debug (15, "CFA_restore_state\n");
           break;
 
-- 
2.13.5