path: root/arch/x86/kernel/ft_event.c

#include <linux/types.h>

#include <litmus/feather_trace.h>

/* the feather trace management functions assume
 * exclusive access to the event table
 */

#ifndef CONFIG_DEBUG_RODATA

#define BYTE_JUMP      0xeb
#define BYTE_JUMP_LEN  0x02

/* for each event, there is an entry in the event table */
struct trace_event {
	long 	id;
	long	count;
	long	start_addr;
	long	end_addr;
};

extern struct trace_event  __start___event_table[];
extern struct trace_event  __stop___event_table[];

/* Workaround: if no events are defined, then the event_table section does not
 * exist and the above references cause linker errors. This could probably be
 * fixed by adjusting the linker script, but it is easier to maintain for us if
 * we simply create a dummy symbol in the event table section.
 */
int __event_table_dummy[0] __attribute__ ((section("__event_table")));

int ft_enable_event(unsigned long id)
{
	struct trace_event* te = __start___event_table;
	int count = 0;
	char* delta;
	unsigned char* instr;

	while (te < __stop___event_table) {
		if (te->id == id && ++te->count == 1) {
			instr  = (unsigned char*) te->start_addr;
			/* make sure we don't clobber something wrong */
			if (*instr == BYTE_JUMP) {
				delta  = (((unsigned char*) te->start_addr) + 1);
				*delta = 0;
			}
		}
		if (te->id == id)
			count++;
		te++;
	}

	printk(KERN_DEBUG "ft_enable_event: enabled %d events\n", count);
	return count;
}

int ft_disable_event(unsigned long id)
{
	struct trace_event* te = __start___event_table;
	int count = 0;
	char* delta;
	unsigned char* instr;

	while (te < __stop___event_table) {
		if (te->id == id && --te->count == 0) {
			instr  = (unsigned char*) te->start_addr;
			if (*instr == BYTE_JUMP) {
				delta  = (((unsigned char*) te->start_addr) + 1);
				*delta = te->end_addr - te->start_addr -
					BYTE_JUMP_LEN;
			}
		}
		if (te->id == id)
			count++;
		te++;
	}

	printk(KERN_DEBUG "ft_disable_event: disabled %d events\n", count);
	return count;
}

int ft_disable_all_events(void)
{
	struct trace_event* te = __start___event_table;
	int count = 0;
	char* delta;
	unsigned char* instr;

	while (te < __stop___event_table) {
		if (te->count) {
			instr  = (unsigned char*) te->start_addr;
			if (*instr == BYTE_JUMP) {
				delta  = (((unsigned char*) te->start_addr)
					  + 1);
				*delta = te->end_addr - te->start_addr -
					BYTE_JUMP_LEN;
				te->count = 0;
				count++;
			}
		}
		te++;
	}
	return count;
}

int ft_is_event_enabled(unsigned long id)
{
	struct trace_event* te = __start___event_table;

	while (te < __stop___event_table) {
		if (te->id == id)
			return te->count;
		te++;
	}
	return 0;
}

#endif