2 files changed, 19 insertions, 0 deletions

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 18ffc347..6c7e0c4a 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,5 +1,10 @@
 2021-12-19  Mark Wielaard  <mark@klomp.org>
 
+        * dwfl_segment_report_module.c (dwfl_segment_report_module): Copy
+        buffer and set xlatefrom.d_buf to ehdr when buffer is not aligned.
+
+2021-12-19  Mark Wielaard  <mark@klomp.org>
+
         * dwfl_segment_report_module.c (dwfl_segment_report_module): Check
         notes filesz. Rewrite reading of GElf_Nhdr.
 
diff --git a/libdwfl/dwfl_segment_report_module.c b/libdwfl/dwfl_segment_report_module.c
index a6d6be85..7f756392 100644
--- a/libdwfl/dwfl_segment_report_module.c
+++ b/libdwfl/dwfl_segment_report_module.c
@@ -367,6 +367,20 @@ dwfl_segment_report_module (Dwfl *dwfl, int ndx, const char *name,
   e_ident = ((const unsigned char *) buffer);
   ei_class = e_ident[EI_CLASS];
   ei_data = e_ident[EI_DATA];
+  /* buffer 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).  */
+  size_t ehdr_align = (ei_class == ELFCLASS32
+                       ? __alignof__ (Elf32_Ehdr)
+                       : __alignof__ (Elf64_Ehdr));
+  if (((uintptr_t) buffer & (ehdr_align - 1)) != 0)
+    {
+      memcpy (&ehdr, buffer,
+              (ei_class == ELFCLASS32
+               ? sizeof (Elf32_Ehdr)
+               : sizeof (Elf64_Ehdr)));
+      xlatefrom.d_buf = &ehdr;
+    }
   switch (ei_class)
     {
     case ELFCLASS32: