x86/build: Add asserts for unwanted sections

In preparation for warning on orphan sections, enforce other
expected-to-be-zero-sized sections (since discarding them might hide
problems with them suddenly gaining unexpected entries).

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200821194310.3089815-25-keescook@chromium.org

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 4b1b936..45d7244 100644 (file)
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -427,6 +427,30 @@ SECTIONS
               SIZEOF(.got.plt) == 0xc,
 #endif
               "Unexpected GOT/PLT entries detected!")
+
+       /*
+        * Sections that should stay zero sized, which is safer to
+        * explicitly check instead of blindly discarding.
+        */
+       .got : {
+               *(.got) *(.igot.*)
+       }
+       ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!")
+
+       .plt : {
+               *(.plt) *(.plt.*) *(.iplt)
+       }
+       ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages detected!")
+
+       .rel.dyn : {
+               *(.rel.*) *(.rel_*)
+       }
+       ASSERT(SIZEOF(.rel.dyn) == 0, "Unexpected run-time relocations (.rel) detected!")
+
+       .rela.dyn : {
+               *(.rela.*) *(.rela_*)
+       }
+       ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) detected!")
 }
 
 #ifdef CONFIG_X86_32