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#include <linux/types.h>
#include <linux/module.h>
#include <asm/cacheflush.h>
#include <asm/sections.h>
#include <litmus/feather_trace.h>
/* the feather trace management functions assume
* exclusive access to the event table
*/
#ifndef CONFIG_RELOCATABLE
#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[];
/* NOTE: The following two functions have been stolen from ftrace.c */
static inline int
within(unsigned long addr, unsigned long start, unsigned long end)
{
return addr >= start && addr < end;
}
static unsigned long text_ip_addr(unsigned long ip)
{
/*
* On x86_64, kernel text mappings are mapped read-only, so we use
* the kernel identity mapping instead of the kernel text mapping
* to modify the kernel text.
*
* For 32bit kernels, these mappings are same and we can use
* kernel identity mapping to modify code.
*/
if (within(ip, (unsigned long)_text, (unsigned long)_etext))
ip = (unsigned long)__va(__pa_symbol(ip));
return ip;
}
/* 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;
set_kernel_text_rw();
set_all_modules_text_rw();
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*) text_ip_addr(
((unsigned long) te->start_addr)
+ 1);
*delta = 0;
}
}
if (te->id == id)
count++;
te++;
}
set_all_modules_text_ro();
set_kernel_text_ro();
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;
set_kernel_text_rw();
set_all_modules_text_rw();
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*) text_ip_addr(
((unsigned long) te->start_addr)
+ 1);
*delta = te->end_addr - te->start_addr -
BYTE_JUMP_LEN;
}
}
if (te->id == id)
count++;
te++;
}
set_all_modules_text_ro();
set_kernel_text_ro();
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;
set_kernel_text_rw();
set_all_modules_text_rw();
while (te < __stop___event_table) {
if (te->count) {
instr = (unsigned char*) te->start_addr;
if (*instr == BYTE_JUMP) {
delta = (unsigned char*) text_ip_addr(
((unsigned long) te->start_addr)
+ 1);
*delta = te->end_addr - te->start_addr -
BYTE_JUMP_LEN;
te->count = 0;
count++;
}
}
te++;
}
set_all_modules_text_ro();
set_kernel_text_ro();
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
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