[PATCH v5 32/36] x86/boot/compressed: Reorganize zero-size section asserts

Kees Cook
2020-07-31T23:08:16Z

For readability, move the zero-sized sections to the end after DISCARDS
and mark them NOLOAD for good measure.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/x86/boot/compressed/vmlinux.lds.S | 42 +++++++++++++++-----------
1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/arch/x86/boot/compressed/vmlinux.lds.S b/arch/x86/boot/compressed/vmlinux.lds.S
index 3c2ee9a5bf43..42dea70a5091 100644
--- a/arch/x86/boot/compressed/vmlinux.lds.S
+++ b/arch/x86/boot/compressed/vmlinux.lds.S
@@ -42,18 +42,16 @@ SECTIONS
*(.rodata.*)
_erodata = . ;
}
- .rel.dyn : {
- *(.rel.*)
- }
- .rela.dyn : {
- *(.rela.*)
- }
- .got : {
- *(.got)
- }
.got.plt : {
*(.got.plt)
}
+ ASSERT(SIZEOF(.got.plt) == 0 ||
+#ifdef CONFIG_X86_64
+ SIZEOF(.got.plt) == 0x18,
+#else
+ SIZEOF(.got.plt) == 0xc,
+#endif
+ "Unexpected GOT/PLT entries detected!")

.data : {
_data = . ;
@@ -85,13 +83,23 @@ SECTIONS
ELF_DETAILS

DISCARDS
-}

-ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!")
-#ifdef CONFIG_X86_64
-ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, "Unexpected GOT/PLT entries detected!")
-#else
-ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0xc, "Unexpected GOT/PLT entries detected!")
-#endif
+ /*
+ * Sections that should stay zero sized, which is safer to
+ * explicitly check instead of blindly discarding.
+ */
+ .got (NOLOAD) : {
+ *(.got)
+ }
+ ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!")

-ASSERT(SIZEOF(.rel.dyn) == 0 && SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations detected!")
+ /* ld.lld does not like .rel* sections being made "NOLOAD". */
+ .rel.dyn : {
+ *(.rel.*)
+ }
+ ASSERT(SIZEOF(.rel.dyn) == 0, "Unexpected run-time relocations (.rel) detected!")
+ .rela.dyn : {
+ *(.rela.*)
+ }
+ ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) detected!")
+}
--
2.25.1