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x86/ftrace: Fix warning and considate ftrace_jmp_replace() and ftrace_call_replace()

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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: Arnd Bergmann <arnd@arndb.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: http://lkml.kernel.org/r/20190304200748.1418790-1-arnd@arndb.de
Fixes: d2a68c4eff ("x86/ftrace: Do not call function graph from dynamic trampolines")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2019-03-04 16:35:22 -05:00
parent 83540fbc88
commit 745cfeaac0
1 changed files with 17 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
arch/x86/kernel/ftrace.c
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@ -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;