Commit b17e8a37 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
Browse files

ftrace: disable ftrace on anomalies in trace start and stop 



Impact: robust feature to disable ftrace on start or stop tracing on error

Currently only the initial conversion to nops will disable ftrace
on an anomaly. But if an anomaly happens on start or stopping of the
tracer, it will silently fail.

This patch adds a check there too, to disable ftrace and warn if the
conversion fails.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f3c7ac40

kernel/trace/ftrace.c

+44 −37
Original line number Diff line number Diff line
@@ -348,6 +348,47 @@ ftrace_record_ip(unsigned long ip) 
	return rec;

}



static void print_ip_ins(const char *fmt, unsigned char *p)

{

	int i;



	printk(KERN_CONT "%s", fmt);



	for (i = 0; i < MCOUNT_INSN_SIZE; i++)

		printk(KERN_CONT "%s%02x", i ? ":" : "", p[i]);

}



static void ftrace_bug(int failed, unsigned long ip,

		       unsigned char *expected,

		       unsigned char *replace)

{

	switch (failed) {

	case -EFAULT:

		FTRACE_WARN_ON_ONCE(1);

		pr_info("ftrace faulted on modifying ");

		print_ip_sym(ip);

		break;

	case -EINVAL:

		FTRACE_WARN_ON_ONCE(1);

		pr_info("ftrace failed to modify ");

		print_ip_sym(ip);

		print_ip_ins(" expected: ", expected);

		print_ip_ins(" actual: ", (unsigned char *)ip);

		print_ip_ins(" replace: ", replace);

		printk(KERN_CONT "\n");

		break;

	case -EPERM:

		FTRACE_WARN_ON_ONCE(1);

		pr_info("ftrace faulted on writing ");

		print_ip_sym(ip);

		break;

	default:

		FTRACE_WARN_ON_ONCE(1);

		pr_info("ftrace faulted on unknown error ");

		print_ip_sym(ip);

	}

}



#define FTRACE_ADDR ((long)(ftrace_caller))



static int
@@ -465,21 +506,12 @@ static void ftrace_replace_code(int enable) 
				if ((system_state == SYSTEM_BOOTING) ||

				    !core_kernel_text(rec->ip)) {

					ftrace_free_rec(rec);

				} else

					ftrace_bug(failed, rec->ip, old, new);

			}

		}

	}

}

}



static void print_ip_ins(const char *fmt, unsigned char *p)

{

	int i;



	printk(KERN_CONT "%s", fmt);



	for (i = 0; i < MCOUNT_INSN_SIZE; i++)

		printk(KERN_CONT "%s%02x", i ? ":" : "", p[i]);

}



static int

ftrace_code_disable(struct dyn_ftrace *rec)
@@ -495,32 +527,7 @@ ftrace_code_disable(struct dyn_ftrace *rec) 


	ret = ftrace_modify_code(ip, call, nop);

	if (ret) {

		switch (ret) {

		case -EFAULT:

			FTRACE_WARN_ON_ONCE(1);

			pr_info("ftrace faulted on modifying ");

			print_ip_sym(ip);

			break;

		case -EINVAL:

			FTRACE_WARN_ON_ONCE(1);

			pr_info("ftrace failed to modify ");

			print_ip_sym(ip);

			print_ip_ins(" expected: ", call);

			print_ip_ins(" actual: ", (unsigned char *)ip);

			print_ip_ins(" replace: ", nop);

			printk(KERN_CONT "\n");

			break;

		case -EPERM:

			FTRACE_WARN_ON_ONCE(1);

			pr_info("ftrace faulted on writing ");

			print_ip_sym(ip);

			break;

		default:

			FTRACE_WARN_ON_ONCE(1);

			pr_info("ftrace faulted on unknown error ");

			print_ip_sym(ip);

		}



		ftrace_bug(ret, ip, call, nop);

		rec->flags |= FTRACE_FL_FAILED;

		return 0;

	}

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