Commit-ID: 5de0a8c0c240338cb5b73363b0673c6aa804bb1c
Gitweb: http://git.kernel.org/tip/5de0a8c0c240338cb5b73363b0673c6aa804bb1c
Author: Steven Rostedt <rost...@goodmis.org>
AuthorDate: Mon, 24 Oct 2016 15:01:48 -0400
Committer: Thomas Gleixner <t...@linutronix.de>
CommitDate: Wed, 26 Oct 2016 12:38:17 +0200
x86: Fix export for mcount and __fentry__
Commit 784d5699eddc5 ("x86: move exports to actual definitions") removed the
EXPORT_SYMBOL(__fentry__) and EXPORT_SYMBOL(mcount) from x8664_ksyms_64.c,
and added EXPORT_SYMBOL(function_hook) in mcount_64.S instead. The problem
is that function_hook isn't a function at all, but a macro that is defined
as either mcount or __fentry__ depending on the support from gcc.
Originally, I thought this was a macro issue, like what __stringify()
is used for. But the problem is a bit deeper. The Makefile.build has
some magic that does post processing of files to create the CRC
bindings. It does some searches for EXPORT_SYMBOL() and because it
finds a macro name and not the actual functions, this causes
function_hook not to be converted into mcount or __fentry__ and they
are missed.
Instead of adding more magic to Makefile.build, just add
EXPORT_SYMBOL() for mcount and __fentry__ where the ifdef is used.
Since this is assembly and not C, it doesn't require being set after
the function is defined.
Signed-off-by: Steven Rostedt <rost...@goodmis.org>
Tested-by: Borislav Petkov <b...@alien8.de>
Cc: Gabriel C <nix.or....@gmail.com>
Cc: Nicholas Piggin <npig...@gmail.com>
Cc: Al Viro <v...@zeniv.linux.org.uk>
Link: http://lkml.kernel.org/r/20161024150148.4f9d9...@gandalf.local.home
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
arch/x86/kernel/mcount_64.S | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/mcount_64.S b/arch/x86/kernel/mcount_64.S
index efe73aa..7b0d3da 100644
--- a/arch/x86/kernel/mcount_64.S
+++ b/arch/x86/kernel/mcount_64.S
@@ -18,8 +18,10 @@
#ifdef CC_USING_FENTRY
# define function_hook __fentry__
+EXPORT_SYMBOL(__fentry__)
#else
# define function_hook mcount
+EXPORT_SYMBOL(mcount)
#endif
/* All cases save the original rbp (8 bytes) */
@@ -295,7 +297,6 @@ trace:
jmp fgraph_trace
END(function_hook)
#endif /* CONFIG_DYNAMIC_FTRACE */
-EXPORT_SYMBOL(function_hook)
#endif /* CONFIG_FUNCTION_TRACER */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
