[PATCH] headers: backport IBT / CFI support

[PATCH] headers: backport IBT / CFI support

[Dimitri John Ledkov]

Kernels that support IBT on x86 require module_init/exit() functions
to have cfi protection included. Backport __CFI_ADDRESSABLE changes
from upstream linux/module.h into backports version of module.h
header.

This results in backported modules correctly pick up CFI protection
only when building against IBT enabled kernels.

Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
---
 backport/backport-include/linux/module.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/backport/backport-include/linux/module.h b/backport/backport-include/linux/module.h
index cd342e0d2fdd..efe970f174ed 100644
--- a/backport/backport-include/linux/module.h
+++ b/backport/backport-include/linux/module.h
@@ -3,6 +3,10 @@
 #include_next <linux/module.h>
 #include <linux/rcupdate.h>
 
+#ifndef __CFI_ADDRESSABLE
+#define __CFI_ADDRESSABLE(fn, __attr)
+#endif
+
 /*
  * The define overwriting module_init is based on the original module_init
  * which looks like this:
@@ -34,6 +38,7 @@ extern void backport_dependency_symbol(void);
 		return initfn();					\
 	}								\
 	int init_module(void) __attribute__((cold,alias("__init_backport")));\
+	__CFI_ADDRESSABLE(init_module, __initdata); \
 	BACKPORT_MOD_VERSIONS
 
 /*
@@ -58,7 +63,8 @@ extern void backport_dependency_symbol(void);
 		exitfn();						\
 		rcu_barrier();						\
 	}								\
-	void cleanup_module(void) __attribute__((cold,alias("__exit_compat")));
+	void cleanup_module(void) __attribute__((cold,alias("__exit_compat"))); \
+	__CFI_ADDRESSABLE(cleanup_module, __exitdata);
 #endif
 
 #endif /* __BACKPORT_LINUX_MODULE_H */
-- 
2.32.0

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Re: [PATCH] headers: backport IBT / CFI support

[Hauke Mehrtens]

On 7/11/22 18:11, Dimitri John Ledkov wrote:
> Kernels that support IBT on x86 require module_init/exit() functions
> to have cfi protection included. Backport __CFI_ADDRESSABLE changes
> from upstream linux/module.h into backports version of module.h
> header.
> 
> This results in backported modules correctly pick up CFI protection
> only when building against IBT enabled kernels.
> 
> Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>

Thank you for your patch I applied it to master.

Hauke
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