diff mbox series

[v4,11/15] x86, relocs: Ignore __typeid__ relocations

Message ID 20210930180531.1190642-12-samitolvanen@google.com (mailing list archive)
State Superseded
Headers show
Series x86: Add support for Clang CFI | expand

Commit Message

Sami Tolvanen Sept. 30, 2021, 6:05 p.m. UTC 
From: Kees Cook <keescook@chromium.org>

The __typeid__* symbols aren't actually relocations, so they can be
ignored during relocation generation.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 arch/x86/tools/relocs.c | 7 +++++++
 1 file changed, 7 insertions(+)

Comments

Josh Poimboeuf Oct. 6, 2021, 3:31 a.m. UTC | #1 
On Thu, Sep 30, 2021 at 11:05:27AM -0700, Sami Tolvanen wrote:
> From: Kees Cook <keescook@chromium.org>
> 
> The __typeid__* symbols aren't actually relocations, so they can be
> ignored during relocation generation.

Then what are they?  It would be good to add that information here.
Sami Tolvanen Oct. 6, 2021, 4:17 p.m. UTC | #2 
On Tue, Oct 5, 2021 at 8:31 PM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> On Thu, Sep 30, 2021 at 11:05:27AM -0700, Sami Tolvanen wrote:
> > From: Kees Cook <keescook@chromium.org>
> >
> > The __typeid__* symbols aren't actually relocations, so they can be
> > ignored during relocation generation.
>
> Then what are they?  It would be good to add that information here.

These relocations are for compiler-generated constants that it uses
for indirect call type checking. I think we can clarify this in the
next version.

Sami
diff mbox series

Patch

diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index 27c82207d387..5304a6037924 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -51,6 +51,7 @@  static const char * const sym_regex_kernel[S_NSYMTYPES] = {
 	"^(xen_irq_disable_direct_reloc$|"
 	"xen_save_fl_direct_reloc$|"
 	"VDSO|"
+	"__typeid__|"
 	"__crc_)",
 
 /*
@@ -811,6 +812,12 @@  static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
 			    symname);
 		break;
 
+	case R_X86_64_8:
+		if (!shn_abs || !is_reloc(S_ABS, symname))
+			die("Non-whitelisted %s relocation: %s\n",
+				rel_type(r_type), symname);
+		break;
+
 	case R_X86_64_32:
 	case R_X86_64_32S:
 	case R_X86_64_64: