ftrace.c

#include <linux/spinlock.h>
#include <linux/hardirq.h>
#include <linux/ftrace.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/list.h>

static const u32 ftrace_nop = 0x01000000;

notrace int ftrace_ip_converted(unsigned long ip)
{
	u32 insn = *(u32 *) ip;

	return (insn == ftrace_nop);
}

notrace unsigned char *ftrace_nop_replace(void)
{
	return (char *)&ftrace_nop;
}

notrace unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
	static u32 call;
	s32 off;

	off = ((s32)addr - (s32)ip);
	call = 0x40000000 | ((u32)off >> 2);

	return (unsigned char *) &call;
}

notrace int
ftrace_modify_code(unsigned long ip, unsigned char *old_code,
		   unsigned char *new_code)
{
	u32 old = *(u32 *)old_code;
	u32 new = *(u32 *)new_code;
	u32 replaced;
	int faulted;

	__asm__ __volatile__(
	"1:	cas	[%[ip]], %[old], %[new]\n"
	"	flush	%[ip]\n"
	"	mov	0, %[faulted]\n"
	"2:\n"
	"	.section .fixup,#alloc,#execinstr\n"
	"	.align	4\n"
	"3:	sethi	%%hi(2b), %[faulted]\n"
	"	jmpl	%[faulted] + %%lo(2b), %%g0\n"
	"	 mov	1, %[faulted]\n"
	"	.previous\n"
	"	.section __ex_table,\"a\"\n"
	"	.align	4\n"
	"	.word	1b, 3b\n"
	"	.previous\n"
	: "=r" (replaced), [faulted] "=r" (faulted)
	: [new] "0" (new), [old] "r" (old), [ip] "r" (ip)
	: "memory");

	if (replaced != old && replaced != new)
		faulted = 2;

	return faulted;
}

notrace int ftrace_update_ftrace_func(ftrace_func_t func)
{
	unsigned long ip = (unsigned long)(&ftrace_call);
	unsigned char old[4], *new;

	memcpy(old, &ftrace_call, 4);
	new = ftrace_call_replace(ip, (unsigned long)func);
	return ftrace_modify_code(ip, old, new);
}

notrace int ftrace_mcount_set(unsigned long *data)
{
	unsigned long ip = (long)(&mcount_call);
	unsigned long *addr = data;
	unsigned char old[4], *new;

	/*
	 * Replace the mcount stub with a pointer to the
	 * ip recorder function.
	 */
	memcpy(old, &mcount_call, 4);
	new = ftrace_call_replace(ip, *addr);
	*addr = ftrace_modify_code(ip, old, new);

	return 0;
}


int __init ftrace_dyn_arch_init(void *data)
{
	ftrace_mcount_set(data);
	return 0;
}