samples/hw_breakpoint: drop use of kallsyms_lookup_name()

The 'data_breakpoint' test code is the only modular user of
kallsyms_lookup_name(), which was exported as part of fixing the test in
f60d24d2ad04 ("hw-breakpoints: Fix broken hw-breakpoint sample module").

In preparation for un-exporting this symbol, switch the test over to using
__symbol_get(), which can be used to place breakpoints on exported
symbols.

Signed-off-by: Will Deacon <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Masami Hiramatsu <[e-mail]>
Reviewed-by: Quentin Perret <[e-mail]>
Cc: K.Prasad <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Frederic Weisbecker <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Miroslav Benes <[e-mail]>
Cc: Petr Mladek <[e-mail]>
Cc: Joe Lawrence <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Linus Torvalds <[e-mail]>

samples/hw_breakpoint/data_breakpoint.c

···
 
 struct perf_event * __percpu *sample_hbp;
 
-static char ksym_name[KSYM_NAME_LEN] = "pid_max";
+static char ksym_name[KSYM_NAME_LEN] = "jiffies";
 module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO);
 MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any"
 			" write operations on the kernel symbol");
···
 {
 	int ret;
 	struct perf_event_attr attr;
+	void *addr = __symbol_get(ksym_name);
+
+	if (!addr)
+		return -ENXIO;
 
 	hw_breakpoint_init(&attr);
-	attr.bp_addr = kallsyms_lookup_name(ksym_name);
+	attr.bp_addr = (unsigned long)addr;
 	attr.bp_len = HW_BREAKPOINT_LEN_4;
 	attr.bp_type = HW_BREAKPOINT_W;
 
···
 static void __exit hw_break_module_exit(void)
 {
 	unregister_wide_hw_breakpoint(sample_hbp);
+	symbol_put(ksym_name);
 	printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name);
 }