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authorJosh Poimboeuf <jpoimboe@redhat.com>2021-01-27 17:18:37 -0600
committerIngo Molnar <mingo@kernel.org>2021-02-17 14:12:42 +0100
commit73f44fe19d359635a607e8e8daa0da4001c1cfc2 (patch)
tree5b4c6bf010e5595ea2cd2314c239ef47503b84b0 /arch
parente59e10f8ef63d42fbb99776a5a112841e798b3b5 (diff)
downloadlinux-73f44fe19d359635a607e8e8daa0da4001c1cfc2.tar.gz
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 'arch')
-rw-r--r--arch/x86/include/asm/static_call.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/include/asm/static_call.h b/arch/x86/include/asm/static_call.h
index c37f11999d0c..cbb67b6030f9 100644
--- a/arch/x86/include/asm/static_call.h
+++ b/arch/x86/include/asm/static_call.h
@@ -37,4 +37,11 @@
#define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) \
__ARCH_DEFINE_STATIC_CALL_TRAMP(name, "ret; nop; nop; nop; nop")
+
+#define ARCH_ADD_TRAMP_KEY(name) \
+ asm(".pushsection .static_call_tramp_key, \"a\" \n" \
+ ".long " STATIC_CALL_TRAMP_STR(name) " - . \n" \
+ ".long " STATIC_CALL_KEY_STR(name) " - . \n" \
+ ".popsection \n")
+
#endif /* _ASM_STATIC_CALL_H */