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authorJosh Poimboeuf <jpoimboe@redhat.com>2021-01-28 02:18:37 +0300
committerIngo Molnar <mingo@kernel.org>2021-02-17 16:12:42 +0300
commit73f44fe19d359635a607e8e8daa0da4001c1cfc2 (patch)
tree5b4c6bf010e5595ea2cd2314c239ef47503b84b0 /tools/objtool
parente59e10f8ef63d42fbb99776a5a112841e798b3b5 (diff)
downloadlinux-73f44fe19d359635a607e8e8daa0da4001c1cfc2.tar.xz
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.c17
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);