[ARM] Avoid dereferencing null pointers
Wed Oct 24 11:36:00 GMT 2018
On Wed, Oct 24, 2018 at 10:37:59AM +0100, Thomas Preudhomme wrote:
> Hi Christophe,
> I'm a bit surprised cmse_scan is run at all in your case. Where you
> targeting an M profile core?
> Regarding sym_hashes[X] being null, under what conditions can a global
> symbol have a null hash?
I sent a little more info to Christophe privately, after I thought a
little more about the problem. Guess I should have sent it to the
You can have sym_hashes[n] being 0 when you have an as-needed library
that wasn't needed (it's loaded but then unloaded).
Note this elflink.c code:
if ((elf_dyn_lib_class (abfd) & DYN_AS_NEEDED) != 0)
unsigned int i;
/* Restore the symbol table. */
old_ent = (char *) old_tab + tabsize;
memset (elf_sym_hashes (abfd), 0,
extsymcount * sizeof (struct elf_link_hash_entry *));
The memset zaps all the sym_hashes, because after restoring the symbol
table to as it was before loading the as-needed library, the symbol
pointers are no longer valid.
The patch I suggest instead of the one Christophe posted is:
diff --git a/bfd/elf32-arm.c b/bfd/elf32-arm.c
index 2c321bbcb6..5adec5e473 100644
@@ -6449,7 +6449,8 @@ elf32_arm_size_stubs (bfd *output_bfd,
Elf_Internal_Sym *local_syms = NULL;
- if (!is_arm_elf (input_bfd))
+ if (!is_arm_elf (input_bfd)
+ || (elf_dyn_lib_class (input_bfd) & DYN_AS_NEEDED) != 0)
num_a8_relocs = 0;
Australia Development Lab, IBM
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