From: Steven Rostedt Date: Mon, 24 Oct 2016 19:01:48 +0000 (-0400) Subject: x86: Fix export for mcount and __fentry__ X-Git-Tag: v4.9-rc3~16^2~1 X-Git-Url: http://git.cascardo.info/?p=cascardo%2Flinux.git;a=commitdiff_plain;h=5de0a8c0c240338cb5b73363b0673c6aa804bb1c 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 Tested-by: Borislav Petkov Cc: Gabriel C Cc: Nicholas Piggin Cc: Al Viro Link: http://lkml.kernel.org/r/20161024150148.4f9d90e4@gandalf.local.home Signed-off-by: Thomas Gleixner --- diff --git a/arch/x86/kernel/mcount_64.S b/arch/x86/kernel/mcount_64.S index efe73aacf966..7b0d3da52fb4 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