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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 /tools/objtool | |
| parent | e59e10f8ef63d42fbb99776a5a112841e798b3b5 (diff) | |
| download | linux-73f44fe19d359635a607e8e8daa0da4001c1cfc2.tar.bz2 | |
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 'tools/objtool')
| -rw-r--r-- | tools/objtool/check.c | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 4bd30315eb62..f2e5e5ce1a05 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -502,8 +502,21 @@ static int create_static_call_sections(struct objtool_file *file) key_sym = find_symbol_by_name(file->elf, tmp); if (!key_sym) { - WARN("static_call: can't find static_call_key symbol: %s", tmp); - return -1; + if (!module) { + WARN("static_call: can't find static_call_key symbol: %s", tmp); + return -1; + } + + /* + * For modules(), the key might not be exported, which + * means the module can make static calls but isn't + * allowed to change them. + * + * In that case we temporarily set the key to be the + * trampoline address. This is fixed up in + * static_call_add_module(). + */ + key_sym = insn->call_dest; } free(key_name); |