Commit 745cfeaa authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

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: stable@vger.kernel.org
Reported-by: default avatarArnd Bergmann <arnd@arndb.de>
Acked-by: default avatarArnd Bergmann <arnd@arndb.de>
Link: http://lkml.kernel.org/r/20190304200748.1418790-1-arnd@arndb.de


Fixes: d2a68c4e ("x86/ftrace: Do not call function graph from dynamic trampolines")
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 83540fbc

arch/x86/kernel/ftrace.c

+17 −25
Original line number Diff line number Diff line
@@ -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;

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