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| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2021-01-27 17:18:37 -0600 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2021-02-17 14:12:42 +0100 |
| commit | 73f44fe19d359635a607e8e8daa0da4001c1cfc2 (patch) | |
| tree | 5b4c6bf010e5595ea2cd2314c239ef47503b84b0 /include/linux/static_call.h | |
| parent | e59e10f8ef63d42fbb99776a5a112841e798b3b5 (diff) | |
| download | lwn-73f44fe19d359635a607e8e8daa0da4001c1cfc2.tar.gz lwn-73f44fe19d359635a607e8e8daa0da4001c1cfc2.zip | |
static_call: Allow module use without exposing static_call_key
When exporting static_call_key; with EXPORT_STATIC_CALL*(), the module
can use static_call_update() to change the function called. This is
not desirable in general.
Not exporting static_call_key however also disallows usage of
static_call(), since objtool needs the key to construct the
static_call_site.
Solve this by allowing objtool to create the static_call_site using
the trampoline address when it builds a module and cannot find the
static_call_key symbol. The module loader will then try and map the
trampole back to a key before it constructs the normal sites list.
Doing this requires a trampoline -> key associsation, so add another
magic section that keeps those.
Originally-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210127231837.ifddpn7rhwdaepiu@treble
Diffstat (limited to 'include/linux/static_call.h')
| -rw-r--r-- | include/linux/static_call.h | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/include/linux/static_call.h b/include/linux/static_call.h index d69dd8b976ca..85ecc789f4ff 100644 --- a/include/linux/static_call.h +++ b/include/linux/static_call.h @@ -138,6 +138,12 @@ struct static_call_key { }; }; +/* For finding the key associated with a trampoline */ +struct static_call_tramp_key { + s32 tramp; + s32 key; +}; + extern void __static_call_update(struct static_call_key *key, void *tramp, void *func); extern int static_call_mod_init(struct module *mod); extern int static_call_text_reserved(void *start, void *end); @@ -165,11 +171,18 @@ extern long __static_call_return0(void); #define EXPORT_STATIC_CALL(name) \ EXPORT_SYMBOL(STATIC_CALL_KEY(name)); \ EXPORT_SYMBOL(STATIC_CALL_TRAMP(name)) - #define EXPORT_STATIC_CALL_GPL(name) \ EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name)); \ EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name)) +/* Leave the key unexported, so modules can't change static call targets: */ +#define EXPORT_STATIC_CALL_TRAMP(name) \ + EXPORT_SYMBOL(STATIC_CALL_TRAMP(name)); \ + ARCH_ADD_TRAMP_KEY(name) +#define EXPORT_STATIC_CALL_TRAMP_GPL(name) \ + EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name)); \ + ARCH_ADD_TRAMP_KEY(name) + #elif defined(CONFIG_HAVE_STATIC_CALL) static inline int static_call_init(void) { return 0; } @@ -216,11 +229,16 @@ static inline long __static_call_return0(void) #define EXPORT_STATIC_CALL(name) \ EXPORT_SYMBOL(STATIC_CALL_KEY(name)); \ EXPORT_SYMBOL(STATIC_CALL_TRAMP(name)) - #define EXPORT_STATIC_CALL_GPL(name) \ EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name)); \ EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name)) +/* Leave the key unexported, so modules can't change static call targets: */ +#define EXPORT_STATIC_CALL_TRAMP(name) \ + EXPORT_SYMBOL(STATIC_CALL_TRAMP(name)) +#define EXPORT_STATIC_CALL_TRAMP_GPL(name) \ + EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name)) + #else /* Generic implementation */ static inline int static_call_init(void) { return 0; } |