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btf: Allow dynamic pointer parameters in kfuncs

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Allow dynamic pointers (struct bpf_dynptr_kern *) to be specified as
parameters in kfuncs. Also, ensure that dynamic pointers passed as argument
are valid and initialized, are a pointer to the stack, and of the type
local. More dynamic pointer types can be supported in the future.

To properly detect whether a parameter is of the desired type, introduce
the stringify_struct() macro to compare the returned structure name with
the desired name. In addition, protect against structure renames, by
halting the build with BUILD_BUG_ON(), so that developers have to revisit
the code.

To check if a dynamic pointer passed to the kfunc is valid and initialized,
and if its type is local, export the existing functions
is_dynptr_reg_valid_init() and is_dynptr_type_expected().

Cc: Joanne Koong <joannelkoong@gmail.com>
Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220920075951.929132-5-roberto.sassu@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Roberto Sassu
2022-09-20 09:59:42 +02:00
committed by Alexei Starovoitov
parent e9e315b4a5
commit b8d31762a0
4 changed files with 52 additions and 5 deletions
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9
include/linux/btf.h
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@@ -52,6 +52,15 @@
#define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */
#define KF_DESTRUCTIVE (1 << 6) /* kfunc performs destructive actions */
/*
* Return the name of the passed struct, if exists, or halt the build if for
* example the structure gets renamed. In this way, developers have to revisit
* the code using that structure name, and update it accordingly.
*/
#define stringify_struct(x) \
({ BUILD_BUG_ON(sizeof(struct x) < 0); \
__stringify(x); })
struct btf;
struct btf_member;
struct btf_type;