PR10323 Some ustack exelib.exp tests fail with prelinked shared libs.

For shared libraries (.dynamic sections) we need the eh frame section
address offset. This is the sh_addr if the shared library isn't prelinked
(since the base load address is zero in that case), otherwise it is
the module start address minus the bias (which also works for the
non-prelinked case).

* translate.cxx (get_unwind_data): Adjust eh_addr for module start and
  bias if module isn't absolute (has no relocations).
* testsuite/systemtap.exelib/ustack.tcl: Accept all prelink tests.

1 files changed, 8 insertions, 3 deletions

diff --git a/translate.cxx b/translate.cxx
index cc634555..a0164661 100644
--- a/translate.cxx
+++ b/translate.cxx
@@ -4438,13 +4438,13 @@ struct unwindsym_dump_context
 
 // Get the .debug_frame end .eh_frame sections for the given module.
 // Also returns the lenght of both sections when found, plus the section
-// address of the eh_frame data.
+// address (offset) of the eh_frame data.
 static void get_unwind_data (Dwfl_Module *m,
 			     void **debug_frame, void **eh_frame,
 			     size_t *debug_len, size_t *eh_len,
 			     Dwarf_Addr *eh_addr)
 {
-  Dwarf_Addr bias = 0;
+  Dwarf_Addr start, bias = 0;
   GElf_Ehdr *ehdr, ehdr_mem;
   GElf_Shdr *shdr, shdr_mem;
   Elf_Scn *scn;
@@ -4452,6 +4452,7 @@ static void get_unwind_data (Dwfl_Module *m,
   Elf *elf;
 
   // fetch .eh_frame info preferably from main elf file.
+  dwfl_module_info (m, NULL, &start, NULL, NULL, NULL, NULL, NULL);
   elf = dwfl_module_getelf(m, &bias);
   ehdr = gelf_getehdr(elf, &ehdr_mem);
   scn = NULL;
@@ -4464,7 +4465,11 @@ static void get_unwind_data (Dwfl_Module *m,
 	  data = elf_rawdata(scn, NULL);
 	  *eh_frame = data->d_buf;
 	  *eh_len = data->d_size;
-	  *eh_addr = shdr->sh_addr;
+	  // For ".dynamic" sections we want the offset, not absolute addr.
+	  if (dwfl_module_relocations (m) > 0)
+	    *eh_addr = shdr->sh_addr - start + bias;
+	  else
+	    *eh_addr = shdr->sh_addr;
 	  break;
 	}
     }