libdwfl: Handle unaligned Nhdr in dwfl_segment_report_module

The xlate functions only handle correctly aligned buffers. But they do
handle src == dest. So if the source buffer isn't aligned correctly
just copy it first into the destination (which is already correctly
aligned).

https://sourceware.org/bugzilla/show_bug.cgi?id=28715

Signed-off-by: Mark Wielaard <mark@klomp.org>

2 files changed, 17 insertions, 0 deletions

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index ac0fbe0f..6015f6b7 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,6 +1,11 @@
 2021-12-19  Mark Wielaard  <mark@klomp.org>
 
         * dwfl_segment_report_module.c (dwfl_segment_report_module): Copy
+        data and set xlatefrom.d_buf to notes when data is not aligned.
+
+2021-12-19  Mark Wielaard  <mark@klomp.org>
+
+        * dwfl_segment_report_module.c (dwfl_segment_report_module): Copy
         ph_buffer and set xlatefrom.d_buf to phdrsp when ph_buffer is not
         aligned.
 
diff --git a/libdwfl/dwfl_segment_report_module.c b/libdwfl/dwfl_segment_report_module.c
index de190e90..72c85070 100644
--- a/libdwfl/dwfl_segment_report_module.c
+++ b/libdwfl/dwfl_segment_report_module.c
@@ -573,6 +573,18 @@ dwfl_segment_report_module (Dwfl *dwfl, int ndx, const char *name,
                   xlatefrom.d_size = filesz;
                   xlateto.d_buf = notes;
                   xlateto.d_size = filesz;
+
+                  /* data may be unaligned, in which case xlatetom would not work.
+                     xlatetom does work when the in and out d_buf are equal (but not
+                     for any other overlap).  */
+                  if ((uintptr_t) data != (align == 8
+                                           ? NOTE_ALIGN8 ((uintptr_t) data)
+                                           : NOTE_ALIGN4 ((uintptr_t) data)))
+                    {
+                      memcpy (notes, data, filesz);
+                      xlatefrom.d_buf = notes;
+                    }
+
                   if (elf32_xlatetom (&xlateto, &xlatefrom, xencoding) == NULL)
                     {
                       free (notes);