moonjuice/kernel_arpi
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

static_call: Allow module use without exposing static_call_key

Browse Source 
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
This commit is contained in:
Josh Poimboeuf
2021-01-27 17:18:37 -06:00
committed by Ingo Molnar
parent e59e10f8ef
commit 73f44fe19d
7 changed files with 149 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

27
tools/include/linux/static_call_types.h
View File

@@ -10,6 +10,7 @@
#define STATIC_CALL_KEY_PREFIX_STR __stringify(STATIC_CALL_KEY_PREFIX)
#define STATIC_CALL_KEY_PREFIX_LEN (sizeof(STATIC_CALL_KEY_PREFIX_STR) - 1)
#define STATIC_CALL_KEY(name) __PASTE(STATIC_CALL_KEY_PREFIX, name)
#define STATIC_CALL_KEY_STR(name) __stringify(STATIC_CALL_KEY(name))
#define STATIC_CALL_TRAMP_PREFIX __SCT__
#define STATIC_CALL_TRAMP_PREFIX_STR __stringify(STATIC_CALL_TRAMP_PREFIX)
@@ -39,17 +40,39 @@ struct static_call_site {
#ifdef CONFIG_HAVE_STATIC_CALL
#define __raw_static_call(name) (&STATIC_CALL_TRAMP(name))
#ifdef CONFIG_HAVE_STATIC_CALL_INLINE
/*
* __ADDRESSABLE() is used to ensure the key symbol doesn't get stripped from
* the symbol table so that objtool can reference it when it generates the
* .static_call_sites section.
*/
#define __STATIC_CALL_ADDRESSABLE(name) \
__ADDRESSABLE(STATIC_CALL_KEY(name))
#define __static_call(name) \
({ \
__ADDRESSABLE(STATIC_CALL_KEY(name)); \
&STATIC_CALL_TRAMP(name); \
__STATIC_CALL_ADDRESSABLE(name); \
__raw_static_call(name); \
})
#else /* !CONFIG_HAVE_STATIC_CALL_INLINE */
#define __STATIC_CALL_ADDRESSABLE(name)
#define __static_call(name) __raw_static_call(name)
#endif /* CONFIG_HAVE_STATIC_CALL_INLINE */
#ifdef MODULE
#define __STATIC_CALL_MOD_ADDRESSABLE(name)
#define static_call_mod(name) __raw_static_call(name)
#else
#define __STATIC_CALL_MOD_ADDRESSABLE(name) __STATIC_CALL_ADDRESSABLE(name)
#define static_call_mod(name) __static_call(name)
#endif
#define static_call(name) __static_call(name)
#else