From b83b43ffc6e4b514ca034a0fbdee01322e2f7022 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Tue, 15 Oct 2019 09:00:55 -0400 Subject: fgraph: Fix function type mismatches of ftrace_graph_return using ftrace_stub The C compiler is allowing more checks to make sure that function pointers are assigned to the correct prototype function. Unfortunately, the function graph tracer uses a special name with its assigned ftrace_graph_return function pointer that maps to a stub function used by the function tracer (ftrace_stub). The ftrace_graph_return variable is compared to the ftrace_stub in some archs to know if the function graph tracer is enabled or not. This means we can not just simply create a new function stub that compares it without modifying all the archs. Instead, have the linker script create a function_graph_stub that maps to ftrace_stub, and this way we can define the prototype for it to match the prototype of ftrace_graph_return, and make the compiler checks all happy! Link: http://lkml.kernel.org/r/20191015090055.789a0aed@gandalf.local.home Cc: linux-sh@vger.kernel.org Cc: Yoshinori Sato Cc: Rich Felker Reported-by: Sami Tolvanen Signed-off-by: Steven Rostedt (VMware) --- include/asm-generic/vmlinux.lds.h | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) (limited to 'include') diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index dae64600ccbf..0f358be551cd 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -111,18 +111,29 @@ #ifdef CONFIG_FTRACE_MCOUNT_RECORD #ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY +/* + * Need to also make ftrace_graph_stub point to ftrace_stub + * so that the same stub location may have different protocols + * and not mess up with C verifiers. + */ #define MCOUNT_REC() . = ALIGN(8); \ __start_mcount_loc = .; \ KEEP(*(__patchable_function_entries)) \ - __stop_mcount_loc = .; + __stop_mcount_loc = .; \ + ftrace_graph_stub = ftrace_stub; #else #define MCOUNT_REC() . = ALIGN(8); \ __start_mcount_loc = .; \ KEEP(*(__mcount_loc)) \ - __stop_mcount_loc = .; + __stop_mcount_loc = .; \ + ftrace_graph_stub = ftrace_stub; #endif #else -#define MCOUNT_REC() +# ifdef CONFIG_FUNCTION_TRACER +# define MCOUNT_REC() ftrace_graph_stub = ftrace_stub; +# else +# define MCOUNT_REC() +# endif #endif #ifdef CONFIG_TRACE_BRANCH_PROFILING -- cgit v1.2.3