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/asm-generic') 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 From 46f9469247c6f4697cbbf37e4b3961120bf07f29 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Mon, 18 Nov 2019 10:41:29 -0500 Subject: ftrace: Rename ftrace_graph_stub to ftrace_stub_graph The ftrace_graph_stub was created and points to ftrace_stub as a way to assign the functon graph tracer function pointer to a stub function with a different prototype than what ftrace_stub has and not trigger the C verifier. The ftrace_graph_stub was created via the linker script vmlinux.lds.h. Unfortunately, powerpc already uses the name ftrace_graph_stub for its internal implementation of the function graph tracer, and even though powerpc would still build, the change via the linker script broke function tracer on powerpc from working. By using the name ftrace_stub_graph, which does not exist anywhere else in the kernel, this should not be a problem. Link: https://lore.kernel.org/r/1573849732.5937.136.camel@lca.pw Fixes: b83b43ffc6e4 ("fgraph: Fix function type mismatches of ftrace_graph_return using ftrace_stub") Reorted-by: Qian Cai Signed-off-by: Steven Rostedt (VMware) --- include/asm-generic/vmlinux.lds.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'include/asm-generic') diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 0f358be551cd..996db32c491b 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -112,7 +112,7 @@ #ifdef CONFIG_FTRACE_MCOUNT_RECORD #ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY /* - * Need to also make ftrace_graph_stub point to ftrace_stub + * Need to also make ftrace_stub_graph point to ftrace_stub * so that the same stub location may have different protocols * and not mess up with C verifiers. */ @@ -120,17 +120,17 @@ __start_mcount_loc = .; \ KEEP(*(__patchable_function_entries)) \ __stop_mcount_loc = .; \ - ftrace_graph_stub = ftrace_stub; + ftrace_stub_graph = ftrace_stub; #else #define MCOUNT_REC() . = ALIGN(8); \ __start_mcount_loc = .; \ KEEP(*(__mcount_loc)) \ __stop_mcount_loc = .; \ - ftrace_graph_stub = ftrace_stub; + ftrace_stub_graph = ftrace_stub; #endif #else # ifdef CONFIG_FUNCTION_TRACER -# define MCOUNT_REC() ftrace_graph_stub = ftrace_stub; +# define MCOUNT_REC() ftrace_stub_graph = ftrace_stub; # else # define MCOUNT_REC() # endif -- cgit