On Mon, 4 Mar 2019 21:07:39 +0100 Arnd Bergmann <[email protected]> wrote:
> Depending on the configuration, ftrace_jmp_replace() sometimes > has no callers at all, since one of the users was removed: > > arch/x86/kernel/ftrace.c:669:23: error: 'ftrace_jmp_replace' defined but not > used [-Werror=unused-function] > > Rather than trying to figure out the correct #ifdef check for this > time, just mark it __maybe_unused and let the compiler drop it > silently. > Actually, its now only used in one place (that git grep shows). Changing it to "__maybe_unused" is a copout, and really shouldn't be something we do for a static function, especially since it's only used in a single location. Also, it's basically identical to ftrace_call_replace(). I'm going to combine the two and move the jmp replace and have it do this instead. -- Steve >From 8e5c6a3255de709ee0d699494243328cd5a11276 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" <[email protected]> Date: Mon, 4 Mar 2019 16:35:22 -0500 Subject: [PATCH] x86/ftrace: Fix warning and considate ftrace_jmp_replace() and ftrace_call_replace() Arnd reported the following compiler warning: arch/x86/kernel/ftrace.c:669:23: error: 'ftrace_jmp_replace' defined but not used [-Werror=unused-function] The ftrace_jmp_replace() function now only has a single user and should be simply moved by that user. But looking at the code, it shows that ftrace_jmp_replace() is similar to ftrace_call_replace() except that instead of using the opcode of 0xe8 it uses 0xe9. It makes more sense to consolidate that function into one implementation that both ftrace_jmp_replace() and ftrace_call_replace() use by passing in the op code separate. The structure in ftrace_code_union is also modified to replace the "e8" field with the more appropriate name "op". Cc: [email protected] Reported-by: Arnd Bergmann <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Fixes: d2a68c4effd8 ("x86/ftrace: Do not call function graph from dynamic trampolines") Signed-off-by: Steven Rostedt (VMware) <[email protected]> --- arch/x86/kernel/ftrace.c | 42 ++++++++++++++++------------------------ 1 file changed, 17 insertions(+), 25 deletions(-) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 8257a59704ae..763d4264d16a 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -49,7 +49,7 @@ int ftrace_arch_code_modify_post_process(void) union ftrace_code_union { char code[MCOUNT_INSN_SIZE]; struct { - unsigned char e8; + unsigned char op; int offset; } __attribute__((packed)); }; @@ -59,20 +59,23 @@ static int ftrace_calc_offset(long ip, long addr) return (int)(addr - ip); } -static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr) +static unsigned char * +ftrace_text_replace(unsigned char op, unsigned long ip, unsigned long addr) { static union ftrace_code_union calc; - calc.e8 = 0xe8; + calc.op = op; calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr); - /* - * No locking needed, this must be called via kstop_machine - * which in essence is like running on a uniprocessor machine. - */ return calc.code; } +static unsigned char * +ftrace_call_replace(unsigned long ip, unsigned long addr) +{ + return ftrace_text_replace(0xe8, ip, addr); +} + static inline int within(unsigned long addr, unsigned long start, unsigned long end) { @@ -664,22 +667,6 @@ int __init ftrace_dyn_arch_init(void) return 0; } -#if defined(CONFIG_X86_64) || defined(CONFIG_FUNCTION_GRAPH_TRACER) -static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr) -{ - static union ftrace_code_union calc; - - /* Jmp not a call (ignore the .e8) */ - calc.e8 = 0xe9; - calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr); - - /* - * ftrace external locks synchronize the access to the static variable. - */ - return calc.code; -} -#endif - /* Currently only x86_64 supports dynamic trampolines */ #ifdef CONFIG_X86_64 @@ -891,8 +878,8 @@ static void *addr_from_call(void *ptr) return NULL; /* Make sure this is a call */ - if (WARN_ON_ONCE(calc.e8 != 0xe8)) { - pr_warn("Expected e8, got %x\n", calc.e8); + if (WARN_ON_ONCE(calc.op != 0xe8)) { + pr_warn("Expected e8, got %x\n", calc.op); return NULL; } @@ -963,6 +950,11 @@ void arch_ftrace_trampoline_free(struct ftrace_ops *ops) #ifdef CONFIG_DYNAMIC_FTRACE extern void ftrace_graph_call(void); +static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr) +{ + return ftrace_text_replace(0xe9, ip, addr); +} + static int ftrace_mod_jmp(unsigned long ip, void *func) { unsigned char *new; -- 2.20.1
