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[Libunwind-devel] [PATCH] Pass relocated address to tdep_get_func_addr

From: Ulrich Weigand
Subject: [Libunwind-devel] [PATCH] Pass relocated address to tdep_get_func_addr
Date: Tue, 17 Dec 2013 15:00:13 +0100 (CET)

[PATCH] Pass relocated address to tdep_get_func_addr

The ppc64 implementation of tdep_get_func_addr would crash when
attempting to retrieve the address of a function in a shared
library.  The problem was that it needs to dereference the
function descriptor, but common code was passing the *unrelocated*
adddress of the descriptor to the tdep_get_func_addr routine.

Instead, common code would attempt to relocate the *result* of
tdep_get_func_addr, which is also wrong: the ppc64 implementation
reads the function address from the in-memory copy of the
descriptor, which is already relocation and contains the final

This patch fixes the problem by relocating the descriptor address
before passing it to tdep_get_func_addr, instead of relocating
the result of tdep_get_func_addr.  Since ppc64 is the only
non-trivial implementation of tdep_get_func_addr, this cannot
affect any other platform.

Signed-off-by: Ulrich Weigand <address@hidden>
 src/elfxx.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/elfxx.c b/src/elfxx.c
index 3d87331..b1afce2 100644
--- a/src/elfxx.c
+++ b/src/elfxx.c
@@ -128,10 +128,11 @@ elf_w (lookup_symbol) (unw_addr_space_t as,
              if (ELF_W (ST_TYPE) (sym->st_info) == STT_FUNC
                  && sym->st_shndx != SHN_UNDEF)
-                 if (tdep_get_func_addr (as, sym->st_value, &val) < 0)
-                   continue;
+                 val = sym->st_value;
                  if (sym->st_shndx != SHN_ABS)
                    val += load_offset;
+                 if (tdep_get_func_addr (as, val, &val) < 0)
+                   continue;
                  Debug (16, "0x%016lx info=0x%02x %s\n",
                         (long) val, sym->st_info, strtab + sym->st_name);

  Dr. Ulrich Weigand
  GNU/Linux compilers and toolchain

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