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[v4,04/17] module: ensure __cfi_check alignment

Message ID 20210331212722.2746212-5-samitolvanen@google.com (mailing list archive)
State New, archived
Headers show
Series Add support for Clang CFI | expand

Commit Message

Sami Tolvanen March 31, 2021, 9:27 p.m. UTC 
CONFIG_CFI_CLANG_SHADOW assumes the __cfi_check() function is page
aligned and at the beginning of the .text section. While Clang would
normally align the function correctly, it fails to do so for modules
with no executable code.

This change ensures the correct __cfi_check() location and
alignment. It also discards the .eh_frame section, which Clang can
generate with certain sanitizers, such as CFI.

Link: https://bugs.llvm.org/show_bug.cgi?id=46293
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Jessica Yu <jeyu@kernel.org>
---
 scripts/module.lds.S | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/scripts/module.lds.S b/scripts/module.lds.S
index 168cd27e6122..2ba9e5ce71df 100644
--- a/scripts/module.lds.S
+++ b/scripts/module.lds.S
@@ -3,10 +3,21 @@ 
  * Archs are free to supply their own linker scripts.  ld will
  * combine them automatically.
  */
+#include <asm/page.h>
+
+#ifdef CONFIG_CFI_CLANG
+# define ALIGN_CFI 		ALIGN(PAGE_SIZE)
+# define SANITIZER_DISCARDS	*(.eh_frame)
+#else
+# define ALIGN_CFI
+# define SANITIZER_DISCARDS
+#endif
+
 SECTIONS {
 	/DISCARD/ : {
 		*(.discard)
 		*(.discard.*)
+		SANITIZER_DISCARDS
 	}
 
 	__ksymtab		0 : { *(SORT(___ksymtab+*)) }
@@ -40,7 +51,14 @@  SECTIONS {
 		*(.rodata..L*)
 	}
 
-	.text : { *(.text .text.[0-9a-zA-Z_]*) }
+	/*
+	 * With CONFIG_CFI_CLANG, we assume __cfi_check is at the beginning
+	 * of the .text section, and is aligned to PAGE_SIZE.
+	 */
+	.text : ALIGN_CFI {
+		*(.text.__cfi_check)
+		*(.text .text.[0-9a-zA-Z_]* .text..L.cfi*)
+	}
 }
 
 /* bring in arch-specific sections */