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Re: RFC: PATCH: PR x86_64/584: Detect call on protected symbol
On Thu, Jan 20, 2005 at 11:17:55AM +0100, Andreas Schwab wrote:
> "H. J. Lu" <hjl@lucon.org> writes:
>
> > I don't think we should worry about anything, like wrong insn, r_offset
> > == 0, jump table or data section.
>
> At least we shouldn't crash.
How about this patch?
H.J.
----
2005-01-20 H.J. Lu <hongjiu.lu@intel.com>
PR 584
* elf64-x86-64.c (is_32bit_relative_branch): New.
(elf64_x86_64_relocate_section): Alllow R_X86_64_PC32 on a
protected function symbol when building shared library for
32bit relative branch instruction.
--- bfd/elf64-x86-64.c.prot 2005-01-11 09:10:28.000000000 -0800
+++ bfd/elf64-x86-64.c 2005-01-20 09:31:25.100049886 -0800
@@ -1745,6 +1745,24 @@ tpoff (struct bfd_link_info *info, bfd_v
return address - htab->tls_size - htab->tls_sec->vma;
}
+/* Is the instruction before OFFSET in CONTENTS a 32bit relative
+ branch? */
+
+static bfd_boolean
+is_32bit_relative_branch (bfd_byte *contents, bfd_vma offset)
+{
+ /* Opcode Instruction
+ 0xe8 call
+ 0xe9 jump
+ 0x0f 0x8x conditional jump */
+ return ((offset > 0
+ && (contents [offset - 1] == 0xe8
+ || contents [offset - 1] == 0xe9))
+ || (offset > 1
+ && contents [offset - 2] == 0x0f
+ && (contents [offset - 1] & 0xf0) == 0x80));
+}
+
/* Relocate an x86_64 ELF section. */
static bfd_boolean
@@ -1950,7 +1968,12 @@ elf64_x86_64_relocate_section (bfd *outp
if (info->shared
&& !SYMBOL_REFERENCES_LOCAL (info, h)
&& (input_section->flags & SEC_ALLOC) != 0
- && (input_section->flags & SEC_READONLY) != 0)
+ && (input_section->flags & SEC_READONLY) != 0
+ && (!h->def_regular
+ || r_type != R_X86_64_PC32
+ || h->type != STT_FUNC
+ || ELF_ST_VISIBILITY (h->other) != STV_PROTECTED
+ || !is_32bit_relative_branch (contents, rel->r_offset)))
{
(*_bfd_error_handler)
(_("%B: relocation %s against `%s' can not be used when making a shared object; recompile with -fPIC"),