ftrace.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/spinlock.h>
#include <linux/hardirq.h>
#include <linux/ftrace.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/list.h>
#include <trace/syscall.h>

#include <asm/ftrace.h>

#ifdef CONFIG_DYNAMIC_FTRACE
static const u32 ftrace_nop = 0x01000000;

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

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

	return call;
}

static int ftrace_modify_code(unsigned long ip, u32 old, u32 new)
{
	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;
}

int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned long ip = rec->ip;
	u32 old, new;

	old = ftrace_call_replace(ip, addr);
	new = ftrace_nop;
	return ftrace_modify_code(ip, old, new);
}

int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned long ip = rec->ip;
	u32 old, new;

	old = ftrace_nop;
	new = ftrace_call_replace(ip, addr);
	return ftrace_modify_code(ip, old, new);
}

int ftrace_update_ftrace_func(ftrace_func_t func)
{
	unsigned long ip = (unsigned long)(&ftrace_call);
	u32 old, new;

	old = *(u32 *) &ftrace_call;
	new = ftrace_call_replace(ip, (unsigned long)func);
	return ftrace_modify_code(ip, old, new);
}
#endif

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

#ifdef CONFIG_DYNAMIC_FTRACE
extern void ftrace_graph_call(void);

int ftrace_enable_ftrace_graph_caller(void)
{
	unsigned long ip = (unsigned long)(&ftrace_graph_call);
	u32 old, new;

	old = *(u32 *) &ftrace_graph_call;
	new = ftrace_call_replace(ip, (unsigned long) &ftrace_graph_caller);
	return ftrace_modify_code(ip, old, new);
}

int ftrace_disable_ftrace_graph_caller(void)
{
	unsigned long ip = (unsigned long)(&ftrace_graph_call);
	u32 old, new;

	old = *(u32 *) &ftrace_graph_call;
	new = ftrace_call_replace(ip, (unsigned long) &ftrace_stub);

	return ftrace_modify_code(ip, old, new);
}

#endif /* !CONFIG_DYNAMIC_FTRACE */

/*
 * Hook the return address and push it in the stack of return addrs
 * in current thread info.
 */
unsigned long prepare_ftrace_return(unsigned long parent,
				    unsigned long self_addr,
				    unsigned long frame_pointer)
{
	unsigned long return_hooker = (unsigned long) &return_to_handler;

	if (unlikely(atomic_read(&current->tracing_graph_pause)))
		return parent + 8UL;

	if (function_graph_enter(parent, self_addr, frame_pointer, NULL))
		return parent + 8UL;

	return return_hooker;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */