diff mbox series

[bpf-next,v9,1/4] compiler_types: Define __rcu as __attribute__((btf_type_tag("rcu")))

Message ID 20221123045356.2323544-1-yhs@fb.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: Add bpf_rcu_read_lock() support | expand

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netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 18105 this patch: 18105
netdev/cc_maintainers warning 2 maintainers not CCed: keescook@chromium.org haoluo@google.com
netdev/build_clang success Errors and warnings before: 4347 this patch: 4347
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netdev/verify_fixes success No Fixes tag
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bpf/vmtest-bpf-next-PR success PR summary
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Commit Message

Yonghong Song Nov. 23, 2022, 4:53 a.m. UTC 
Currently, without rcu attribute info in BTF, the verifier treats
rcu tagged pointer as a normal pointer. This might be a problem
for sleepable program where rcu_read_lock()/unlock() is not available.
For example, for a sleepable fentry program, if rcu protected memory
access is interleaved with a sleepable helper/kfunc, it is possible
the memory access after the sleepable helper/kfunc might be invalid
since the object might have been freed then. To prevent such cases,
introducing rcu tagging for memory accesses in verifier can help
to reject such programs.

To enable rcu tagging in BTF, during kernel compilation,
define __rcu as attribute btf_type_tag("rcu") so __rcu information can
be preserved in dwarf and btf, and later can be used for bpf prog verification.

Acked-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
 include/linux/compiler_types.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index eb0466236661..7c1afe0f4129 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -49,7 +49,8 @@  static inline void __chk_io_ptr(const volatile void __iomem *ptr) { }
 # endif
 # define __iomem
 # define __percpu	BTF_TYPE_TAG(percpu)
-# define __rcu
+# define __rcu		BTF_TYPE_TAG(rcu)
+
 # define __chk_user_ptr(x)	(void)0
 # define __chk_io_ptr(x)	(void)0
 /* context/locking */